Holographic relations between theories have become an important theme in quantum gravity research. These relations entail that a theory without gravity is equivalent to a gravitational theory with an extra spatial dimension. The idea of holography was first proposed in 1993 by ‘t Hooft on the basis of his studies of evaporating black holes. Soon afterwards the holographic AdS/CFT duality was introduced, which since has been intensively studied in the string theory community and beyond. Recently, Verlinde has proposed that Newton’s law of gravitation can be related holographically to the ‘thermodynamics of information’ on screens. I discuss the last two scenarios, with special attention to the status of the holographic relation in them and to the question of whether they make gravity and spacetime emergent. I conclude that only Verlinde’s scheme instantiates emergence in a clear and uncontroversial way. I suggest that a reinterpretation of AdS/CFT may create room for the emergence of spacetime and gravity there as well.
Talk given at Oxford Philosophy of Physics, LSE's Sigma Club, the Munich Center for Mathematical Philosophy, Carlo Rovelli's 60th birthday conference.
I construe dualities in physics as particular cases of theoretical equivalence. The question then naturally arises whether duality is compatible with emergence. For the the focus of emergence is on novelty rather than on equivalence.
In the first part of the talk, I review recent work dealing with this question. I exhibit two ways in which duality and equivalence can be made compatible, and I give an example of emergence in gauge/gravity dualities: dualities between a theory of gravity in (d+1) dimensions and a quantum field theory (QFT) in d dimensions.
In the second part of the talk, I present new results on the question whether diffeomorphisms in gravity theories emerge from QFTs. I critically assess the following idea, taken from the physics literature: given that (a) the QFT is not a diffeomorphism invariant theory, and that (b) there is a duality between the QFT and the gravity theory, are we entitled to (c) conclude that the diffeomorphisms of the gravity theory emerge from the QFT?
I argue that one must distinguish different kinds of diffeomorphisms: some diffeomorphisms are ‘invisible’ to the QFT: all of the QFT’s quantities are invariant under them, therefore the QFT does not ‘see’ them. But other diffeomorphisms are ‘visible’ to the QFT. The invisible diffeomorphisms prompt a ‘Bulk Argument’, in analogy with the Hole Argument. The analysis of emergence is different for these different kinds of diffeomorphisms, and I discuss the way in which we can speak of emergence of diffeomorphisms in gauge/gravity dualities.
(1) The document discusses the concepts of emergence and reduction in physics, specifically arguing that they pose a false dichotomy as they are logically independent.
(2) It provides examples where emergence occurs alongside reduction, such as the emergence of classical behavior from quantum mechanics in certain limits, and the emergence of thermodynamic laws and properties from statistical mechanics.
(3) The key point is that reduction, viewed as deduction, allows for novelty through the choices made in taking limits, such as which symmetries to break or states to keep. So emergence and reduction can be compatible.
Pittsburgh talk on Emergence and in Gauge/Gravity DualitiesSebastian De Haro
This document discusses emergence and duality in gauge/gravity dualities. It begins by introducing gauge/gravity dualities, which relate a theory of gravity in (d+1) dimensions to a quantum field theory without gravity in d dimensions. The document then discusses two ways in which emergence can occur in theories related by duality: 1) the duality map breaks down at some level of fine-graining, and 2) an approximation scheme is applied to each side of the duality, only holding the duality approximately. Even if gauge/gravity duality is exact, emergence can occur through the second way by approximating the full string theory with a semiclassical gravity theory, where the radial direction corresponds to energy scale
Vasil Penchev. Gravity as entanglement, and entanglement as gravityVasil Penchev
1. The document discusses interpreting gravity as entanglement by investigating the conditions under which general relativity and quantum mechanics can be mapped to each other mathematically.
2. It outlines a strategy to interpret entanglement as inertial mass and gravitational mass, and to view gravity as another interpretation of any quantum mechanical or mechanical movement.
3. This would allow gravity to be incorporated into the standard model by generalizing the concept of quantum field to include entanglement, represented by a cyclic Yin-Yang mathematical structure.
Talk given at Oxford Philosophy of Physics, LSE's Sigma Club, the Munich Center for Mathematical Philosophy, Carlo Rovelli's 60th birthday conference.
I construe dualities in physics as particular cases of theoretical equivalence. The question then naturally arises whether duality is compatible with emergence. For the the focus of emergence is on novelty rather than on equivalence.
In the first part of the talk, I review recent work dealing with this question. I exhibit two ways in which duality and equivalence can be made compatible, and I give an example of emergence in gauge/gravity dualities: dualities between a theory of gravity in (d+1) dimensions and a quantum field theory (QFT) in d dimensions.
In the second part of the talk, I present new results on the question whether diffeomorphisms in gravity theories emerge from QFTs. I critically assess the following idea, taken from the physics literature: given that (a) the QFT is not a diffeomorphism invariant theory, and that (b) there is a duality between the QFT and the gravity theory, are we entitled to (c) conclude that the diffeomorphisms of the gravity theory emerge from the QFT?
I argue that one must distinguish different kinds of diffeomorphisms: some diffeomorphisms are ‘invisible’ to the QFT: all of the QFT’s quantities are invariant under them, therefore the QFT does not ‘see’ them. But other diffeomorphisms are ‘visible’ to the QFT. The invisible diffeomorphisms prompt a ‘Bulk Argument’, in analogy with the Hole Argument. The analysis of emergence is different for these different kinds of diffeomorphisms, and I discuss the way in which we can speak of emergence of diffeomorphisms in gauge/gravity dualities.
(1) The document discusses the concepts of emergence and reduction in physics, specifically arguing that they pose a false dichotomy as they are logically independent.
(2) It provides examples where emergence occurs alongside reduction, such as the emergence of classical behavior from quantum mechanics in certain limits, and the emergence of thermodynamic laws and properties from statistical mechanics.
(3) The key point is that reduction, viewed as deduction, allows for novelty through the choices made in taking limits, such as which symmetries to break or states to keep. So emergence and reduction can be compatible.
Pittsburgh talk on Emergence and in Gauge/Gravity DualitiesSebastian De Haro
This document discusses emergence and duality in gauge/gravity dualities. It begins by introducing gauge/gravity dualities, which relate a theory of gravity in (d+1) dimensions to a quantum field theory without gravity in d dimensions. The document then discusses two ways in which emergence can occur in theories related by duality: 1) the duality map breaks down at some level of fine-graining, and 2) an approximation scheme is applied to each side of the duality, only holding the duality approximately. Even if gauge/gravity duality is exact, emergence can occur through the second way by approximating the full string theory with a semiclassical gravity theory, where the radial direction corresponds to energy scale
Vasil Penchev. Gravity as entanglement, and entanglement as gravityVasil Penchev
1. The document discusses interpreting gravity as entanglement by investigating the conditions under which general relativity and quantum mechanics can be mapped to each other mathematically.
2. It outlines a strategy to interpret entanglement as inertial mass and gravitational mass, and to view gravity as another interpretation of any quantum mechanical or mechanical movement.
3. This would allow gravity to be incorporated into the standard model by generalizing the concept of quantum field to include entanglement, represented by a cyclic Yin-Yang mathematical structure.
Space is not fundamental (although time might be). Talk at the 2010 Philosophy of Science Association Meeting, Montreal. By Sean Carroll, http://preposterousuniverse.com/
Three levels of scientific hypotheses are curves/functions, models, and theories. Curves represent empirical relationships between variables, models incorporate adjustable parameters, and theories are broad sets of principles. Curve fitting involves three steps: 1) determining variables, 2) selecting a model family of curves, and 3) estimating parameter values for the best fitting curve. Models play an essential role by representing families of curves and allowing indirect confirmation of hypotheses. Overlooking models can misconstrue processes like measurement and curve fitting.
What We (Don't) Know About the Beginning of the UniverseSean Carroll
A plenary talk at the January 2017 meeting of the American Astronomical Society, on whether the universe truly had a beginning, and what might have come before.
This document provides an overview of general philosophy of science and introduces some key concepts in logic that are relevant to philosophy of science. It discusses how general philosophy of science seeks to understand science across many disciplines rather than focusing on a single field. It also introduces deductive logic and different types of arguments, focusing on the distinction between valid and sound arguments. The document examines how logic has been used as a tool in philosophy of science but may have limitations, as scientific theories are not always logical deductions from evidence alone.
This document summarizes and compares different models of a beam balance experiment. It finds that simpler models are often nested within more complex models. The simplest model (SIMP) represents the mass ratio as a single parameter, while a more complex model (COMP) adds a second parameter. An even more complex model (COMPTOO) adds a third object on the beam. The document examines problems with selecting the best model based only on fit to the data, and discusses alternatives like parsimony and falsification.
This document summarizes a research paper on chaotic group actions. It begins with an abstract discussing how group actions can be considered "chaotic" if they exhibit sensitive dependence on initial conditions and have a dense set of points with finite orbits. The paper then provides definitions and examples of chaotic group actions, discussing how the concept generalizes the definition of chaotic maps. It explores which groups can admit chaotic dynamics on topological spaces and which spaces admit chaotic group actions. Specifically, it shows a group has a chaotic action if and only if it is residually finite. It also constructs examples of chaotic actions and proves several theorems about when group actions are chaotic.
This document discusses the relationship between algebraic formulations of quantum mechanics, algebraic geometry, and Bohm's notion of pre-space. It examines how the Heisenberg algebra and Dirac's ket can be viewed through this framework. Fermion and boson algebras are presented based on methods that generalize functions without reference to space-time. The implications of these algebraic structures for studying pre-space are discussed. Quantum mechanics is interpreted as being fundamentally algebraic in nature, with bras and kets viewed as elements within the underlying dynamical algebra.
This document provides an overview of research on multi-metric gravity theories. It begins by introducing linear massive gravity and how it generates an extra ghost degree of freedom. Developments in nonlinear massive gravity and bi-metric gravity resolved this by introducing interaction terms between the metrics. The document then discusses proposals for tri-metric and multi-metric gravity, but notes the ghost problem remains unresolved in tri-metric gravity. It proceeds to analyze the Hamiltonian of an example tri-metric gravity theory to investigate the presence of ghosts. Finally, it contrasts metric and vielbein formulations of multiple interacting spin-2 fields.
Dynamical Systems Methods in Early-Universe CosmologiesIkjyot Singh Kohli
The document discusses applying dynamical systems methods to develop models of the early universe. Specifically, it discusses:
1. Applying these methods to the Einstein field equations to obtain cosmological models that are spatially homogeneous but anisotropic.
2. Describing the process of analyzing the dynamics of these models, which involves identifying invariant sets, equilibrium points, monotone functions, and bifurcations in the parameter space.
3. The importance of numerical methods in understanding the global behavior of these systems, since analytical methods are often limited to local analysis near equilibrium points.
This document discusses rational ergodicity properties of rank-one transformations. It proves that all rank-one transformations are subsequence boundedly rationally ergodic, and that there exist rank-one transformations that are not weakly rationally ergodic. It also proves that rank-one transformations with a bounded sequence of cuts satisfy the stronger property of being boundedly rationally ergodic. The document provides background on rational ergodicity, rank-one transformations, and cutting and stacking constructions.
This document proposes an alternative theory called Fluid Space Theory to explain the galaxy rotation problem without dark matter. It suggests that space-time flows inward around massive objects like galaxies due to velocity fields, and that this inward flow accounts for the "missing" mass. The theory applies principles of special relativity to argue that the inward moving space-time becomes compressed, so its volume decreases without limit as it approaches light speed, resolving issues with an unlimited accumulation of space-time near massive objects. It proposes this inward flowing and compressing space-time can explain the observed faster rotation speeds of galaxies.
Berlin - Conceptual Aspects of Gauge-Gravity DualitySebastian De Haro
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms for those who already suffer from conditions like depression and anxiety.
Epstemologic controversy on quantum operatorsraalbe autor
This document discusses the epistemological controversy around the role of space and time in quantum operators. Specifically:
- There is debate around whether space and time have their own algebraic operators in quantum theory. Some argue they do, which would imply particles have "coordinates of position", though these cannot be determined with perfect precision.
- The document analyzes the proper role of space and time in non-relativistic quantum physics. It finds the "Heisenberg fourth relation" concerning time and energy has a different basis than assumed.
- It also discusses that in quantum physics, particles are not point-like objects, so there are no true "coordinates of position". The conceptual structure of quantum physics does not
This document is Albert Einstein's book "Relativity: The Special and General Theory" which was published in 1916. It aims to give an accessible introduction to the theory of relativity for readers without an extensive mathematical background. The book is divided into three parts, with Part I focusing on Einstein's Special Theory of Relativity. It begins by discussing the meaning of geometrical propositions and their relationship to empirical objects in nature. It then introduces the concept of coordinate systems and how they are used to specify positions in space and time.
This document provides an overview of fractal geometry. It begins with an abstract that outlines how fractal patterns found in nature will be used to introduce the concept of fractals. It then provides a brief history of fractals, covering mathematicians like Georg Cantor and Benoit Mandelbrot who contributed to the discovery and study of fractals. The document goes on to examine key properties of fractals in depth, including recursion, self-similarity, iteration, and fractal dimension. It also provides examples of well-known fractals like the Sierpinski triangle and Mandelbrot set to illustrate these properties.
1. Several theories propose that nothingness or a mathematical/logical structure could be the main source of the universe's existence. These include the ideas that nothingness is pure energy/negativity that can fluctuate and create existence, or that logical consequences or relations emerging from nothingness could explain the universe.
2. However, there are various criticisms for each theory. For the nothingness theories, it is unclear why existence should necessarily arise from nothingness. The mathematical universe hypotheses face issues like how to account for the observed simplicity of the real universe and the problem of measure or existence. While promising, each theory currently has outstanding objections.
3. Some alternatives propose that certain things like logic, observers, or mathematical
OBC | String theory and quests for unification of fundamental forces of natureOut of The Box Seminar
Mirjam Cvetič, University of Pennsylvania, Philadelphia, USA
String theory and quests for unification of fundamental forces of nature
http://obc2012.outofthebox.si/
SIGMA Study of Industrial Gravity Measurement Applications: Objectives and wo...George Tuckwell
SIGMA (Study of Industrial Gravity Measurement Applications) is a £350k Innovate UK funded research project investigating the next generation of quantum technology based geophysical instruments which aims to quantify their potential to create a step change in how the ground is investigated
Space is not fundamental (although time might be). Talk at the 2010 Philosophy of Science Association Meeting, Montreal. By Sean Carroll, http://preposterousuniverse.com/
Three levels of scientific hypotheses are curves/functions, models, and theories. Curves represent empirical relationships between variables, models incorporate adjustable parameters, and theories are broad sets of principles. Curve fitting involves three steps: 1) determining variables, 2) selecting a model family of curves, and 3) estimating parameter values for the best fitting curve. Models play an essential role by representing families of curves and allowing indirect confirmation of hypotheses. Overlooking models can misconstrue processes like measurement and curve fitting.
What We (Don't) Know About the Beginning of the UniverseSean Carroll
A plenary talk at the January 2017 meeting of the American Astronomical Society, on whether the universe truly had a beginning, and what might have come before.
This document provides an overview of general philosophy of science and introduces some key concepts in logic that are relevant to philosophy of science. It discusses how general philosophy of science seeks to understand science across many disciplines rather than focusing on a single field. It also introduces deductive logic and different types of arguments, focusing on the distinction between valid and sound arguments. The document examines how logic has been used as a tool in philosophy of science but may have limitations, as scientific theories are not always logical deductions from evidence alone.
This document summarizes and compares different models of a beam balance experiment. It finds that simpler models are often nested within more complex models. The simplest model (SIMP) represents the mass ratio as a single parameter, while a more complex model (COMP) adds a second parameter. An even more complex model (COMPTOO) adds a third object on the beam. The document examines problems with selecting the best model based only on fit to the data, and discusses alternatives like parsimony and falsification.
This document summarizes a research paper on chaotic group actions. It begins with an abstract discussing how group actions can be considered "chaotic" if they exhibit sensitive dependence on initial conditions and have a dense set of points with finite orbits. The paper then provides definitions and examples of chaotic group actions, discussing how the concept generalizes the definition of chaotic maps. It explores which groups can admit chaotic dynamics on topological spaces and which spaces admit chaotic group actions. Specifically, it shows a group has a chaotic action if and only if it is residually finite. It also constructs examples of chaotic actions and proves several theorems about when group actions are chaotic.
This document discusses the relationship between algebraic formulations of quantum mechanics, algebraic geometry, and Bohm's notion of pre-space. It examines how the Heisenberg algebra and Dirac's ket can be viewed through this framework. Fermion and boson algebras are presented based on methods that generalize functions without reference to space-time. The implications of these algebraic structures for studying pre-space are discussed. Quantum mechanics is interpreted as being fundamentally algebraic in nature, with bras and kets viewed as elements within the underlying dynamical algebra.
This document provides an overview of research on multi-metric gravity theories. It begins by introducing linear massive gravity and how it generates an extra ghost degree of freedom. Developments in nonlinear massive gravity and bi-metric gravity resolved this by introducing interaction terms between the metrics. The document then discusses proposals for tri-metric and multi-metric gravity, but notes the ghost problem remains unresolved in tri-metric gravity. It proceeds to analyze the Hamiltonian of an example tri-metric gravity theory to investigate the presence of ghosts. Finally, it contrasts metric and vielbein formulations of multiple interacting spin-2 fields.
Dynamical Systems Methods in Early-Universe CosmologiesIkjyot Singh Kohli
The document discusses applying dynamical systems methods to develop models of the early universe. Specifically, it discusses:
1. Applying these methods to the Einstein field equations to obtain cosmological models that are spatially homogeneous but anisotropic.
2. Describing the process of analyzing the dynamics of these models, which involves identifying invariant sets, equilibrium points, monotone functions, and bifurcations in the parameter space.
3. The importance of numerical methods in understanding the global behavior of these systems, since analytical methods are often limited to local analysis near equilibrium points.
This document discusses rational ergodicity properties of rank-one transformations. It proves that all rank-one transformations are subsequence boundedly rationally ergodic, and that there exist rank-one transformations that are not weakly rationally ergodic. It also proves that rank-one transformations with a bounded sequence of cuts satisfy the stronger property of being boundedly rationally ergodic. The document provides background on rational ergodicity, rank-one transformations, and cutting and stacking constructions.
This document proposes an alternative theory called Fluid Space Theory to explain the galaxy rotation problem without dark matter. It suggests that space-time flows inward around massive objects like galaxies due to velocity fields, and that this inward flow accounts for the "missing" mass. The theory applies principles of special relativity to argue that the inward moving space-time becomes compressed, so its volume decreases without limit as it approaches light speed, resolving issues with an unlimited accumulation of space-time near massive objects. It proposes this inward flowing and compressing space-time can explain the observed faster rotation speeds of galaxies.
Berlin - Conceptual Aspects of Gauge-Gravity DualitySebastian De Haro
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms for those who already suffer from conditions like depression and anxiety.
Epstemologic controversy on quantum operatorsraalbe autor
This document discusses the epistemological controversy around the role of space and time in quantum operators. Specifically:
- There is debate around whether space and time have their own algebraic operators in quantum theory. Some argue they do, which would imply particles have "coordinates of position", though these cannot be determined with perfect precision.
- The document analyzes the proper role of space and time in non-relativistic quantum physics. It finds the "Heisenberg fourth relation" concerning time and energy has a different basis than assumed.
- It also discusses that in quantum physics, particles are not point-like objects, so there are no true "coordinates of position". The conceptual structure of quantum physics does not
This document is Albert Einstein's book "Relativity: The Special and General Theory" which was published in 1916. It aims to give an accessible introduction to the theory of relativity for readers without an extensive mathematical background. The book is divided into three parts, with Part I focusing on Einstein's Special Theory of Relativity. It begins by discussing the meaning of geometrical propositions and their relationship to empirical objects in nature. It then introduces the concept of coordinate systems and how they are used to specify positions in space and time.
This document provides an overview of fractal geometry. It begins with an abstract that outlines how fractal patterns found in nature will be used to introduce the concept of fractals. It then provides a brief history of fractals, covering mathematicians like Georg Cantor and Benoit Mandelbrot who contributed to the discovery and study of fractals. The document goes on to examine key properties of fractals in depth, including recursion, self-similarity, iteration, and fractal dimension. It also provides examples of well-known fractals like the Sierpinski triangle and Mandelbrot set to illustrate these properties.
1. Several theories propose that nothingness or a mathematical/logical structure could be the main source of the universe's existence. These include the ideas that nothingness is pure energy/negativity that can fluctuate and create existence, or that logical consequences or relations emerging from nothingness could explain the universe.
2. However, there are various criticisms for each theory. For the nothingness theories, it is unclear why existence should necessarily arise from nothingness. The mathematical universe hypotheses face issues like how to account for the observed simplicity of the real universe and the problem of measure or existence. While promising, each theory currently has outstanding objections.
3. Some alternatives propose that certain things like logic, observers, or mathematical
OBC | String theory and quests for unification of fundamental forces of natureOut of The Box Seminar
Mirjam Cvetič, University of Pennsylvania, Philadelphia, USA
String theory and quests for unification of fundamental forces of nature
http://obc2012.outofthebox.si/
SIGMA Study of Industrial Gravity Measurement Applications: Objectives and wo...George Tuckwell
SIGMA (Study of Industrial Gravity Measurement Applications) is a £350k Innovate UK funded research project investigating the next generation of quantum technology based geophysical instruments which aims to quantify their potential to create a step change in how the ground is investigated
The document discusses the concept of center of gravity and how it relates to an object's stability. It defines center of gravity as the point where an object's entire weight seems to act and explains that an object's stability depends on the position of its center of gravity relative to its base. Specifically, an object will be stable if tilting moves the center of gravity higher within the base, unstable if tilting lowers it outside the base, and neutrally stable if tilting does not change the height. Real-life examples like buses and lamps are designed with low, broad bases to lower the center of gravity and increase stability.
1 banasik-the implementation of the mipaa directives in australiaifa2012_2
The document analyzes budgets from Australian federal, state, and local governments over an 11-year period to determine the implementation of the Madrid International Plan of Action on Ageing (MIPAA). It finds that while governments funded initiatives benefiting older people indirectly, direct funding of programs tailored to older adults' needs declined after 2009. Specifically, the federal government supported 5 out of 8 policy areas identified in Australia's National Strategy for an Ageing Population initially but not continuously throughout the period. Direct funding of older adult programs ceased in the 2011/2012 federal budget.
La oxitocina es una hormona producida en el hipotálamo que regula dos funciones principales: 1) La contracción del útero durante el parto y 2) La eyección de la leche de los alveolos mamarios hacia el pezón durante la lactancia. La oxitocina también juega un papel en otras funciones como la contracción de la musculatura lisa del útero después del parto, la eyaculación y la liberación de fluido seminal.
The Eclipse Public License (EPL) defines key terms like Contributor and Program. It grants Contributors a non-exclusive copyright license to reproduce and distribute their Contributions in source and object code form. The license requires compliance with the agreement terms, including effectively disclaiming warranties and excluding liability for damages. Commercial distributors may accept responsibilities for end users but are solely responsible for any claims or warranties related to their products.
Лицензирование СПО в российских условиях. Анализ проблем и решенийLWandWs
В презентации рассматриваются основные особенности лицензирования свободного ПО в России, приводятся ссылки на Законодательство РФ, предлагаются варианты предупреждения и решения проблем, возможных при использовании нелицензионных программных продуктов и решений, распространяемых по лицензии GPL.
This document outlines key findings from a literature review on aging with developmental disabilities. It discusses how individuals with developmental disabilities experience accelerated aging, showing signs of aging in their 40s-50s that others typically see in their 60s-70s. Health challenges like obesity, mental health issues, and diseases like Alzheimer's are more prevalent. Barriers to healthy aging include a lack of tailored health promotion and difficulties with identification and diagnosis of issues. Recommendations include improving practitioner education, regular health monitoring from age 40, and empowering individuals to participate in their own healthcare.
Este documento narra la historia de cómo la autora le enseñó a su madre, Dora Lilia Reyes Beltran, a usar un celular y aplicaciones como WhatsApp. Explica que su madre no tenía conocimientos tecnológicos debido a que no pudo ir a la escuela, por lo que la autora se propuso compartir sus conocimientos sobre el uso básico de un celular, incluyendo cómo buscar contactos, revisar registros de llamadas y usar WhatsApp para comunicarse con otras personas e intercambiar fotos. También le explicó a
Este documento presenta la historia de Carmen Yulieth Fuentes Parra, una estudiante de 15 años en Colombia, y su trabajo con Bladimir Fuentes Corredor, un comerciante de 45 años, para enseñarle cómo usar una computadora y acceder a YouTube e Internet a través del programa Redvolución. El documento describe las lecciones sobre las partes de la computadora, el navegador, cómo ingresar a YouTube y buscar videos, y cómo Bladimir aprendió lo fácil que es usar Internet gracias a Redvolución.
The document proposes a method for extracting and integrating information from different websites using crowdsourcing. It involves using a DOM tree analysis and K-means clustering to identify keywords. Crowdsourcing is then used twice: first to select keywords and then to label data and generate extraction rules. An experiment on books, movies, and music websites showed the method could accurately extract data up to 98%. The method reduces the workload for individual workers and costs compared to previous methods.
This document discusses green open spaces and defines the public and private sectors as well as two kinds of green open spaces - preserved open spaces and built open spaces. It aims to teach about the public and private sectors' roles in green open spaces.
Florence Duality Talk: Reduction and Emergence in Holographic Scenarios for G...Sebastian De Haro
Philosophical talk about the status of dualities and the emergence of gravity in two holographic scenarios: 1) AdS/CFT and 2) Verlinde's scenario of emergent gravity.
Talk on the philosophy of dualities, in particular AdS/CFT. Joint talk delivered with Jeremy Butterfield at the Biennial Meeting of the Philosophy of Science Association, Chicago, 7 Nov. 2014.
Reality in a few thermodynamic reference frames: Statistical thermodynamics ...Vasil Penchev
Boltzmann's theory introduced statistical mechanics and viewed thermodynamic phenomena as emerging from the mechanical motion of atoms and molecules. This represented a shift where [1] the size of entities changed from macroscopic to microscopic, [2] the relation between theory and empirical observation changed from direct coincidence to indirect testability, and [3] the relation between the whole and parts changed from harmonized to reductionist. Gibbs's theory was also reductionist but eliminated atoms, instead using ensembles of systems in phase space. Einstein's theory viewed reality as both macroscopic and microscopic, consisting of a whole and parts, generating a relative theoretical model to reconcile mismatches between theories rather than directly solving problems.
Gravity as entanglement, and entanglement as gravityVasil Penchev
1) The document discusses the relationship between gravity and quantum entanglement, exploring the possibility that they are equivalent or closely connected concepts.
2) It outlines an approach to interpret gravity in terms of a generalized quantum field theory that includes entanglement, which could explain why gravity cannot be quantized.
3) The key idea is that entanglement expressed "outside" of space-time points looks like gravity "inside", and vice versa, with gravity representing a smooth constraint on the quantum behavior of entities imposed by all others.
Einstein's theories of relativity include the special and general theories. The special theory, published in 1905, deals with inertial frames of reference and the constancy of the speed of light. The general theory, published in 1915, extends these concepts to accelerated frames and explains gravity as a consequence of spacetime curvature. Key findings include spacetime being dynamic, light bending in gravity, and the equivalence of mass and energy. The Michelson-Morley experiment's null results disproved the ether hypothesis and supported Einstein's postulate that the speed of light is independent of motion.
This document discusses the connection between deterministic evolution over time and differential equations from philosophical, historical, and mathematical perspectives.
From a philosophical viewpoint, the author argues that deterministic motion can be associated with semigroups and is characterized by differential equations with time derivatives. Historically, the exponential function and semigroup theory emerged from efforts to solve linear differential equations. Mathematically, the document outlines the basic theory of uniformly, strongly, and σ(X,F)-continuous semigroups of linear operators and their generators.
This essay is a compilation of ideas, opinions, and conjectures from two previous essays, "Is Science Solving the Reality Riddle," and "Order, Chaos, and the End of Reductionism," and was expanded to include subsequent essays. It is very much a work in progress and has been repeatedly amended when necessary. The author concludes that current scientific theories are incomplete and limit our understanding of nature in a fundamental way, the current description of how the universe eveolved is wrong, and a new evolutionary paradigm is presented that explains both the physical and mental evolutionary processes.
Short Presentation of the Theory of Everything. It includes the discovery of an extra spatial dimension and that the whole Universe is traveling at the speed of light (radially). This discovery refutes General Relativity and all the current scientific framework.
This document provides an overview of uncertainty relations in physics. It discusses canonically conjugate variables, which are pairs of variables that are Fourier transform duals and related by Noether's theorem. Position and momentum, energy and time, and angle turned and angular momentum are provided as examples of conjugate variable pairs. The document explains that conjugate variables cannot be measured precisely at the same time according to the uncertainty principle. It provides the mathematical formulation of the uncertainty principle for common conjugate variable pairs and discusses the physical significance of limiting the precision of complementary observable measurements.
Mind blowing theories about the universe and realityBASKARAN P
The document discusses several scientific theories about the universe and reality, including:
- The Big Bang Theory, which proposes that the universe began as an infinitesimally small, infinitely hot and dense singularity around 13.7 billion years ago.
- The Bubble Theory or Eternal Inflation theory, which extends the Big Bang Theory by proposing the inflationary phase of the universe's expansion lasts forever in some regions, producing an infinite multiverse.
- String Theory, which proposes that elementary particles are different vibrational states of fundamental strings and aims to be a theory of quantum gravity by unifying quantum mechanics and general relativity.
This document summarizes a physics research project on models of cosmological inflation. The project analytically and numerically evaluates single field models, multifield hybrid models, and f(R) models arising from modified gravity. It calculates the dynamics of these models and makes theoretical predictions for observables like the scalar spectral index and tensor-to-scalar ratio. These predictions are compared to experimental data to determine which models produce viable inflationary theories. The project reproduces known single field results and explores higher-order f(R) terms, showing they can only be a small correction to Starobinsky inflation. It also evaluates a multifield hybrid potential and how two fields can combine to produce inflation.
2012 09 duality and ontic structural realism bristolIoan Muntean
Dualities in string theory relate different regions of the theory's moduli space where coupling constants may take on different values, potentially interchanging what is viewed as fundamental versus composite. These dualities do not provide unification or explanation according to the author, but may still reveal deeper underlying structures without requiring a single deeper theory. The document discusses various interpretations of string theory and issues regarding background dependence, structuralism, and the role of dualities.
Is Mass at Rest One and the Same? A Philosophical Comment: on the Quantum I...Vasil Penchev
The way, in which quantum information can unify quantum mechanics (and therefore the standard
model) and general relativity, is investigated. Quantum information is defined as the generalization
of the concept of information as to the choice among infinite sets of alternatives. Relevantly, the
axiom of choice is necessary in general. The unit of quantum information, a qubit is interpreted
as a relevant elementary choice among an infinite set of alternatives generalizing that of a bit.
The invariance to the axiom of choice shared by quantum mechanics is introduced: It constitutes
quantum information as the relation of any state unorderable in principle (e.g. any coherent quantum
state before measurement) and the same state already well-ordered (e.g. the well-ordered statistical
ensemble of the measurement of the quantum system at issue). This allows of equating the classical and
quantum time correspondingly as the well-ordering of any physical quantity or quantities and their
coherent superposition. That equating is interpretable as the isomorphism of Minkowski space and
Hilbert space. Quantum information is the structure interpretable in both ways and thus underlying
their unification. Its deformation is representable correspondingly as gravitation in the deformed
pseudo-Riemannian space of general relativity and the entanglement of two or more quantum
systems. The standard model studies a single quantum system and thus privileges a single reference
frame turning out to be inertial for the generalized symmetry [U(1)]X[SU(2)]X[SU(3)] “gauging” the
standard model. As the standard model refers to a single quantum system, it is necessarily linear
and thus the corresponding privileged reference frame is necessary inertial. The Higgs mechanism
U(1) → [U(1)]X[SU(2)] confirmed enough already experimentally describes exactly the choice of the
initial position of a privileged reference frame as the corresponding breaking of the symmetry. The
standard model defines ‘mass at rest’ linearly and absolutely, but general relativity non-linearly
and relatively. The “Big Bang” hypothesis is additional interpreting that position as that of the
“Big Bang”. It serves also in order to reconcile the linear standard model in the singularity of the
“Big Bang” with the observed nonlinearity of the further expansion of the universe described very
well by general relativity. Quantum information links the standard model and general relativity in
another way by mediation of entanglement. The linearity and absoluteness of the former and the
nonlinearity and relativeness of the latter can be considered as the relation of a whole and the same
whole divided into parts entangled in general.
General Relativity is inconsistent with quantum theory which
leaves our understanding of nature incomplete and unsatisfactory. The now 80 years old quest for a consistent theory of quantum gravity has so far almost entirely focused on mathematical consistency. But as of recently the possibility to look for observational evidence has received an increased amount of attention, as a tool to provide guidance for the construction of of the theory.
Here, I summarize recent developments in the search for
experimental signatures for quantum gravitational effects and how these help to put constraints on the theory-construction. Some of the topics that I will cover are the prospects of finding Planck scale effects in gamma ray bursts, in neutral Kaon oscillations, or with massive quantum oscillators. If time allows, I will also comment on the search for holographic noise and how to find evidence for space-time discreteness.
Quantum phenomena modeled by interactions between many classical worldsLex Pit
Michael J. W. Hall, Dirk-André Deckert, and Howard M. Wiseman
ABSTRACT
We investigate whether quantum theory can be understood as the continuum limit of a mechanical theory, in which there is a huge, but finite, number of classical “worlds,” and quantum effects arise solely from a universal interaction between these worlds, without reference to any wave function. Here, a “world” means an entire universe with well-defined properties, determined by the classical configuration of its particles and fields. In our approach, each world evolves deterministically, probabilities arise due to ignorance as to which world a given observer occupies, and we argue that in the limit of infinitely many worlds the wave function can be recovered (as a secondary object) from the motion of these worlds. We introduce a simple model of such a “many interacting worlds” approach and show that it can reproduce some generic quantum phenomena—such as Ehrenfest’s theorem, wave packet spreading, barrier tunneling, and zero-point energy—as a direct consequence of mutual repulsion between worlds. Finally, we perform numerical simulations using our approach. We demonstrate, first, that it can be used to calculate quantum ground states, and second, that it is capable of reproducing, at least qualitatively, the double-slit interference phenomenon.
DOI: http://dx.doi.org/10.1103/PhysRevX.4.041013
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3. For gravity to vanish as the second law of thermodynamics requires, gravity and entropy must be the same phenomenon and gravity must end when maximum entropy is reached in an isolated system like the universe.
The document discusses Gerard 't Hooft's proposal of a superdeterministic interpretation of quantum mechanics that denies experimenters have free will in choosing experimental parameters. It outlines the assumptions behind Bell's Inequalities, which are violated by quantum mechanics experiments, and argues that superdeterminism is not tenable as it would require an implausibly complex physical mechanism to predetermine experimenters' choices. While a deterministic universe may be possible, the document concludes that superdeterminism cannot validly explain quantum mechanics given the assumptions required are weakly defended.
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We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
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cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
PPT on Alternate Wetting and Drying presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
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Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
HUMAN EYE By-R.M Class 10 phy best digital notes.pdf
Berlin Slides Dualities and Emergence of Space-Time and Gravity
1. Dualities and Emergent Gravity:
AdS/CFT and Verlinde’s Scheme
Sebastian de Haro
University of Amsterdam and University of Cambridge
Emergent Time and Emergent Space in Quantum Gravity
AEI Potsdam, 18 December 2014
Partly based on PhilSci 10606 with D. Dieks, J. van Dongen
2. 2
• Duality and emergence of space-time have
been a strong focus in quantum gravity and
string theory research in recent years
4. 4
• The notion of ‘emergence’ of space-time
and/or gravity is often attached to the
existence of a ‘duality’.
• An argument along the following lines is often
made:
a) Theory F ('fundamental') and theory G ('gravity')
are dual to one another.
b) Theory F does not contain gravity (and/or
space-time) whereas theory G does.
c) Therefore space-time (and/or gravity) emerges
in theory G. Theory F is to be regarded as more
fundamental.
5. • But this argument is problematic: it replaces ‘duality’ by
‘emergence’.
• Duality is a symmetric relation, whereas emergence is not
symmetric
• We need to explain what breaks the symmetry
• Emergence of space-time requires more than simply ‘the
space-time being dual to something that is not spatio-
temporal’.
• It might lead to bad heuristics for constructing new theories, in
particular when we are told that we should not pursue theory
G but just work on theory F.
• I will discuss the notions of duality and emergence in
holographic scenarios:
• Duality: AdS/CFT
• Emergence: Verlinde’s holographic scenario and AdS/CFT
• I will only discuss the possible emergence of gravity
together with one, spatial dimension.
• This is a non-trivial task: for obtaining the right classical
dynamics for the metric is hard!
6. ’t Hooft’s Holographic Hypothesis
• The total number of degrees of freedom, 𝑛, in a region of spacetime
containing a black hole, is:
𝑛 =
𝑆
log 2
=
𝐴
4𝐺log 2
• Hence, “we can represent all that happens inside [a volume] by
degrees of freedom on the surface”
• “This suggests that quantum gravity should be described entirely by a
topological quantum field theory, in which all degrees of freedom can
be projected on to the boundary”
• “We suspect that there simply are no more degrees of freedom to
talk about than the ones one can draw on a surface [in bit/Planck
length2]. The situation can be compared with a hologram of a three
dimensional image on a two dimensional surface”.
7. ’t Hooft’s Holographic Hypothesis
• The observables “can best be described as if“ they were Boolean
variables on a lattice, which suggests that the description on the
surface only serves as one possible representation.
• Nevertheless, 't Hooft's account more often assumes that the
fundamental ontology is the one of the degrees of freedom that scale
with the spacetime's boundary. He argued that quantum gravity
theories that are formulated in a four dimensional spacetime, and
that one would normally expect to have a number of degrees of
freedom that scales with the volume, must be “infitely correlated" at
the Planck scale.
• The explanatory arrow here clearly goes from surface to bulk, with
the plausible implication that the surface theory should be taken as
more basic than the theory of the enclosed volume.
• There is no indication that a notion of emergence is relevant here.
8. ’t Hooft’s Holographic Hypothesis
• ’t Hooft’s paper wavers between boundary and bulk as fundamental
ontologies.
• There is an interpretative tension here, that resurfaces in other
contexts where there are dualities.
9. Philosophical concerns regarding
holographic dualities:
•Can one decide which side of the duality is
more fundamental?
•Is one facing emergence of space, time,
and/or gravity?
9
10. Plan
•Duality: AdS/CFT
• Introduction
• Duality
• Renormalization group
• Diffeomorphism invariance and background
independence
• Interpretation
•Emergence: Verlinde’s scenario and AdS/CFT
10
11. AdS/CFT
• 𝐷-dim. anti-de Sitter space
• Can be extended to (AL)AdS
• In local coordinates:
d𝑠2
=
ℓ2
𝑟2
d𝑟2
− d𝑡2
+ d𝐱2
• Fields 𝜙 𝑟, 𝑥
• Mass 𝑚
• CFT on ℝ 𝐷−1
• QFT with a fixed point,
other backgrounds
• Operators 𝒪 𝑥
• Dimension Δ
11
12. Duality Statement
•One-to-one map of states and quantities
(observables) between distinct theories preserving
certain structures.
•String theory in (AL)AdS space = QFT on boundary
•Fields 𝜙 𝑟, 𝑥 ↔ Operators 𝒪 𝑥
•Partition function 𝑑 = 𝐷 − 1 :
𝑍string 𝑟Δ −𝑑 𝜙 𝑟, 𝑥
𝑟=0
= 𝜙 0 𝑥 = 𝑒 d 𝑑 𝑥 𝜙 0 𝑥 𝒪 𝑥
CFT
•Physical equivalence, mathematical structure
different
•Large distance ↔ high energy divergences
•Strictly speaking, the AdS/CFT correspondence has
the status of a ‘conjecture’, though there is massive
evidence for it (and it is usually called a
‘correspondence’: compare e.g. Fermat’s last
‘theorem’ before it was proven!)
(1)
12
13. Renormalization Group
• Radial integration: • Wilsonian renormalization:
Λ𝑏Λ0
𝑘
integrate out
New cutoff 𝑏Λ
rescale 𝑏Λ → Λ until 𝑏 → 0
AdS 𝑟
𝜕AdS 𝑟 𝜕AdS 𝜖
new boundary condition
integrate out
IR cutoff 𝜖 in AdS ↔ UV cutoff Λ in QFT
13
14. Conditions for AdS/CFT Duality
• What could lead to the failure of AdS/CFT as a duality?
• Two conditions must be met for this bijection to exist. The observable
structures of these theories should be:
i. Complete (sub-) structures of observables, i.e. no other observables can
be written down than (1): this structure of observables contains what the
theories regard to be ‘physical’ independently on each side of the duality.
ii. Identical, i.e. the (sub-) structures of observables are identical to each
other.
If ii. is not met, we can have a weaker form of the conjecture: a relation that is
non-exact. For instance, if the duality holds only in some particular regime of the
coupling constants.
• There are no good reasons to believe that i. fails.
• Whether ii. is met is still open, but all available evidence indicates that it is
satisfied, including some non-perturbative tests.
14
15. Remarks on Background Independence
• Theories of gravity are usually required to be ‘background independent’. In
Einstein’s theory of relativity, the metric is a dynamical quantity, determined
from the equations of motion rather than being fixed from the outset.
• The concept of ‘background independence’ does not have a fixed meaning, see
Belot (2011).
• Here I will adopt a ‘minimalist approach’: a theory is background independent
if it is generally covariant and its formulation does not make reference to a
background/fixed metric. In particular, the metric is determined dynamically
from the equations of motion.
• In this minimalist sense, classical gravity in AdS is fully background
independent: Einstein’s equations with negative cosmological constant.
• Quantum corrections do not change this conclusion: they appear perturbatively as
covariant higher-order corrections to Einstein’s theory.
• Could background independence be broken by a choice of particular solutions
of Einstein’s equations?
• The equations of motion do not determine the boundary conditions, which need to
be specified additionally (de Haro et al. 2001).
• But this is not a restriction on the class of solutions considered; as in classical
mechanics, the equations of motion simply do not contain the informtion about the
boundary/initial conditions.
• This does not seem a case of lack of background independence of the theory. At
most, it may lead to spontaneous breaking of the symmetry by a choice of a
particular solution. 15
16. Diffeomorphism Invariance of (1)
• I have discussed background independence of the equations of
motion. What about the observables?
• Partition function (1):
• It depends on the boundary conditions on the metric (as do the classical
solutions).
• It is diffeomorphism invariant, for those diffeomorphisms that preserve the
asymptotic form of the metric.
• Other observables obtained by taking derivatives of (1): they
transform as tensors under these diffeomorphisms. These
observables are covariant, for odd d (=boundary dimension):
• For odd 𝑑:
• Invariance/covariance holds.
• For even 𝑑:
• Bulk diffeomorphisms that yield conformal transformations of the boundary
metric are broken due to IR divergences (holographic Weyl anomaly). Is this
bad?
16
𝑍string 𝑟Δ −𝑑
𝜙 𝑟, 𝑥
𝑟=0
= 𝜙 0 𝑥 = 𝑒 d 𝑑 𝑥 𝜙 0 𝑥 𝒪 𝑥
CFT
(1)
17. Diffeomorphism Invariance (even 𝑑)
• The breaking of diffeomorphism invariance exactly mirrors the
breaking of conformal invariance by quantum effects in the CFT.
• The partition function now depends on the representative of the
conformal structure picked for regularization.
• The observables (1) such as the stress-tensor no longer transform
covariantly, but pick up an anomalous term.
• Anomalies are usually quantum effects, proportional to ℏ. Here,
the anomaly is (inversely) proportional to Newton’s constant 𝐺.
• The anomaly is robust: it is fully non-linear and it does not rely on
classical approximations.
• This anomaly does not lead to any inconsistencies because the
metric is not dynamical in the CFT (see Huggett’s talk).
17
18. Philosophical Questions
•Is one side of the duality more fundamental?
• If QFT more fundamental, space-time could be ‘emergent’
• If the duality is only approximate: room for emergence
(e.g. thermodynamics vs. atomic theory)
• If duality holds good: one-to-one relation between the
values of physical quantities. In this case we have to
give the duality a physical interpretation
18
19. Interpretation
•External view: meaning of observables is externally
fixed. Duality relates different physical quantities
• No empirical equivalence, numbers correspond to
different physical quantities
• The symmetry of the terms related by duality is broken by
the different physical interpretation given to the symbols
• Example: 𝑟 fixed by the interpretation to mean ‘radial
distance’ in the bulk theory. In the boundary theory, the
corresponding symbol is fixed to mean ‘renormalization
group scale’. The two symbols clearly describe different
physical quantities. More generally, the two theories
describe different physics hence are not empirically
equivalent
• Only one of the two sides provides a correct
interpretation of empirical reality 19
20. Interpretation
•Internal point of view:
• The meaning of the symbols is not fixed beforehand
• There is only one set of observables that is described by
the two theories. The two descriptions are equivalent. No
devisable experiment could tell one from the other (each
observation can be reinterpreted in the ‘dual’ variables)
• Cannot decide which description is superior. One
formulation may be superior on practical grounds (e.g.
computational simplicity in a particular regime)
• On this formulation we would normally say that we have
two formulations of one theory, not two different
theories
20
21. Interpretation
•The internal point of view seems more natural for
theories of the whole world
•Even if one views a theory as a partial description of
empirical reality, in so far as one takes it seriously in
a particular domain of applicability, the internal
view seems the more natural description.
• Compare: position/momentum duality in QM. Equivalence of
frames in special relativity.
21
22. Interpretation
•The internal point of view seems more natural for
theories of the whole world
•Even if one views a theory as a partial description of
empirical reality, in so far as one takes it seriously in
a particular domain of applicability, the internal
view seems the more natural description.
• Compare: position/momentum duality in QM. Equivalence of
frames in special relativity.
• We should worry about the measurement problem, but it
is not necessarily part of what is here meant by ‘theories
of the whole world’, because the statement is still true in
the classical limit, where we get Einstein gravity.
22
23. •Butterfields’s puzzling scenario about truth (2014): Does
reality admit two or more complete descriptions which
• (Different): are not notational variants of each other; and yet
• (Success): are equally and wholly successful by all epistemic
criteria one should impose?
•On the external view, the two theories are not equally
successful because they describe different physical
quantities: only one of them may describe this world.
•On the internal view, the two descriptions are equivalent
hence equally successful.
• If they turn out to be notational variants of each other (e.g.
different choices of gauge in a bigger theory) then the
philosophical conclusion is less exciting, but new physics is to
be expected. This is what often happens when there is a
duality. Currently there is no indication that the two theories
are notational variants of each other.
• If the two theories are not notational variants of each other,
then we do face the puzzling scenario! 23
24. • On the external view, the two theories describe
different physics
• The dual theory is only a tool that might be useful, but does
not describe the physics of our world
• Here, the idea of ‘emergence’ does not suggest itself
because whichever side describes our world, it does not
emerge from something else.
• On the internal view there is a one-to-one relation
between the values of physical quantities
• Again emergence does not suggest itself: the two
descriptions are equivalent
• If the duality is only approximate then there may be room
for emergence of space-time (analogy: thermodynamics
vs. statistical mechanics)
24
Emergence
25. Example: Verlinde’s Scheme
• Working out the idea of an approximate duality for the
specific case of Newtonian gravity
• Gravity is special: it is universal. It applies to all matter
and energy, regardless of specific interactions; it seems
to relate to space itself
• This universality reminds one of the universal character
of thermodynamical behavior, which is independent of
microscopic details
• Gravity distinguishes itself from other forces because it
is difficult to quantize; is it fundamentally different?
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26. Guiding idea about force as a
thermodynamic phenomenon
•Entropic processes: as a result of random motion of its
microscopic constituents a physical system will end up in a
state of greater entropy, i.e. higher probability: the system
seems to be directed
•Although there are no forces on the microscopic level, on
the thermodynamic level the system appears driven, and this
can be described by a “macroscopic force”
•Like a stretched polymer. Spring constant not a fundamental
constant but depends on 𝑇!
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27. Applying this to Gravity
•Start with a theory without gravity on a two-
dimensional screen, e.g. the surface of a sphere
•Holography: this theory codifies information about
matter in an additional spatial dimension (“in the
bulk”)
•The microscopic details of this gravitation-free
theory remain unspecified: it is a theory of
holographic degrees of freedom (Verlinde calls
them “bits”)
•Make gravity appear as a macroscopic
thermodynamic phenomenon
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28. Working this out
•Imagine a sphere, whose area is divided into small
cells with each one degree of freedom (“bit”). Call
this the ‘system’.
•On the sphere an entropic process takes place: this
system is coupled to a reservoir at fixed
temperature (the ‘environment’), and the
distribution of dof of the system tends to
equilibrium.
•This process will correspond to gravitational motion
inside the sphere
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29. Appearance of Space
•In the surface theory, there are no spatial dimensions
other than those within the surface itself
•Consider several spheres, namely different surface
theories that relate to each other via ‘renormalization’
(‘coarse-graining’ steps)
•Coarse-graining:
• Removing some dof reduces the area of the sphere
• ‘Coarse-grained’ theories describe less dof, i.e. less space
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30. Appearance of Space
• Thus, a spatial dimension 𝑥 appears as a bookkeeping device
that records the level of coarse graining on the sphere
• Entropy grows when a particle is thrown in (Bekenstein):
Δ𝑆 ~ 𝑚 ∆𝑥
Picture: http://media02.hongkiat.com/black-white-photo-water/black-and-white-drops.jpg
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31. The Appearance of Gravity
1) Holography: number of bits in the reservoir
𝑁 =
𝐴 𝑐3
𝐺ℏ
=
4𝜋𝑅2 𝑐3
𝐺ℏ
2) Equipartition: 𝐸 = 𝑀𝑐2 ~ 𝑁 𝑇
3) Bekenstein: Δ𝑆 ~ 𝑚 ∆𝑥
4) Second law of thermodynamics: 𝐹 = 𝑇
∆𝑆
∆𝑥
j 31
32. The Appearance of Gravity
1) Holography: number of bits in the reservoir
𝑁 =
𝐴 𝑐3
𝐺ℏ
=
4𝜋𝑅2
𝑐3
𝐺ℏ
2) Equipartition: 𝐸 = 𝑀𝑐2 ~ 𝑁 𝑇
3) Bekenstein: Δ𝑆 ~ 𝑚 ∆𝑥
4) Second law of thermodynamics: 𝐹 = 𝑇
∆𝑆
∆𝑥
From which we get Newton’s law: 𝐹 ~
𝑀𝑚
𝑅2
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33. Some Distinctions in Verlinde’s Scheme
• We should not regard the process of ‘throwing a
particle in’ as increasing the number of bits in the
theory on the sphere
• Remember duality: the bits on the screen are dual to the
particles near the screen
• Throwing a particle in thus decreases the number of bits in the
system. More precisely: it increases the number of bits in the
reservoir and decreases the number of bits in the system.
• So the boundary theory is not a theory about what is inside the
screen (the reservoir) but about the bits that are within one
Compton wavelength of the screen (the system)
• The relation 𝑁 =
𝐴𝑐3
𝐺ℏ
is the definition of the relation
between the bulk and the boundary. It is not a
statement about entropy. We can rescale the area and
rescale ℏ at the same time without changing anything
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35. • The holographic relation may well be a bijective map.
• There is no reason in this case to think that one side is
more fundamental than the other (left-right).
• But the thermodynamic limit introduces the emergence
of gravity in an uncontroversial sense (top-bottom).
Does Gravity Emerge?
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36. At which level does this require holography?
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• The emergence of gravity only requires approximate holography.
• In Verlinde’s scheme, the microscopic bulk theory can be
dispensed with.
37. Emergence of Space and Gravity
• Gravity could thus emerge in the same way (via coarse
graining) in other situations where gauge/gravity duality
does not hold exactly (e.g. cosmological scenarios: dS/CFT).
• But this idea can be applied more generally to AdS/CFT,
where the renormalization group flow introduces coarse
graining over high-energy degrees of freedom.
• In this case, Einstein gravity may emerge from the
fundamental bulk theory, whether the latter contains gravity
or not.
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38. Conclusions
•In holographic scenarios with an exact duality, the
microscopic surface theory is not necessarily more
fundamental than the microscopic bulk theory.
• The bulk does not emerge from the boundary in such
cases.
•However, the appearance of gravity in the
thermodynamic limit makes it a clear case of
emergence, connected with robustness and novelty
of behavior. This robustness explains the universality
of gravity.
•That gravity is emergent could give rise to new
predictions: the law of gravity is not exact but subject
to fluctuations.
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