72nd ICREA Colloquium
Laws, Chance and Quantum Randomness
The laws of nature could be indeterministic, in the sense that they simply fail to be deterministic. There are numerous examples of determinism-failure even in classical physics. A different idea entirely is that of irreducibly probabilistic laws of nature: laws whose contents are, or entail, putative objective probabilities or chances for events.
In my work I raise concerns about how well we understand the notion of an irreducible probabilistic law in general. I explain some of these philosophical concerns, and how they motivate interest in the Bohmian approach to quantum physics. I also discuss the relation between Bohmian quantum mechanics and the theoretical and experimental results of physicists such as Acín, Gisin, Colbeck and Renner.
Talk on "Cosmic Anomalies" by Peter Coles given at the Conference "Current and Future Challenges of the Dark and Early Universes", Niels Bohr Institute, Copenhagen, 8-12 August 2011.
Data from the Wilkinson Microwave Anisotropy Probe (WMAP) and, more recently, the Planck Mission, have provided us with unprecedented quantitative information that has helped to establish the current `concordance' cosmology. These observations have also revealed a number of features that we do not understand so well, prompting suggestions of departures from the standard framework. In this talk I will review a few of these interesting such anomalies, touching on the methods used to identify them and what their physical origin might be if they are not simply experimental artifacts of some sort.
69th ICREA Colloquium "Everything you always wanted to know about creating a ...ICREA
Why would you, decent and exemplary ICREA researchers, ever want to get involved in the creation of a spin-off company? In this colloquium we will take a stroll on the ‘dark side of science’: its commercial exploitation. The talk aims at covering both the practical and the institutional points of view. To that end, Joan Seoane, who started his own company ‘Mosaic Biomedicals’ in 2012, will share his experience with all of us. And Emilià Pola will present the vision and the position of ICREA as an institution, or in other words, why an institution like ICREA gets involved in such mundane activities.
Based on recent work on quantum gravity and the holographic principle I argue that, instead of thinking of the universe as a 'bubble out of nothing', we should think of space, time, and gravity as emerging 'out of information'.
General relativity vs. quantum mechanics issues of foundations uv 1_oct2018SOCIEDAD JULIO GARAVITO
En este seminario, nos enfocaremos en los asuntos fundamentales relacionados con los pilares actuales de la física, y discutiremos los problemas para la creación de una teoría cuántica de la gravitación, es decir Teoría de Cuerdas, Super-Simetría o SUSY, o una Teoría del Todo.
Talk on "Cosmic Anomalies" by Peter Coles given at the Conference "Current and Future Challenges of the Dark and Early Universes", Niels Bohr Institute, Copenhagen, 8-12 August 2011.
Data from the Wilkinson Microwave Anisotropy Probe (WMAP) and, more recently, the Planck Mission, have provided us with unprecedented quantitative information that has helped to establish the current `concordance' cosmology. These observations have also revealed a number of features that we do not understand so well, prompting suggestions of departures from the standard framework. In this talk I will review a few of these interesting such anomalies, touching on the methods used to identify them and what their physical origin might be if they are not simply experimental artifacts of some sort.
69th ICREA Colloquium "Everything you always wanted to know about creating a ...ICREA
Why would you, decent and exemplary ICREA researchers, ever want to get involved in the creation of a spin-off company? In this colloquium we will take a stroll on the ‘dark side of science’: its commercial exploitation. The talk aims at covering both the practical and the institutional points of view. To that end, Joan Seoane, who started his own company ‘Mosaic Biomedicals’ in 2012, will share his experience with all of us. And Emilià Pola will present the vision and the position of ICREA as an institution, or in other words, why an institution like ICREA gets involved in such mundane activities.
Based on recent work on quantum gravity and the holographic principle I argue that, instead of thinking of the universe as a 'bubble out of nothing', we should think of space, time, and gravity as emerging 'out of information'.
General relativity vs. quantum mechanics issues of foundations uv 1_oct2018SOCIEDAD JULIO GARAVITO
En este seminario, nos enfocaremos en los asuntos fundamentales relacionados con los pilares actuales de la física, y discutiremos los problemas para la creación de una teoría cuántica de la gravitación, es decir Teoría de Cuerdas, Super-Simetría o SUSY, o una Teoría del Todo.
Dynamical Systems Modeling in NeuroscienceYohan John
A lecture I gave recently as an introduction to computational neuroscience.
Note: the "pentagon of science" was proposed by Eric L Schwartz, a professor at BU who coined the term "computational neuroscience".
My inaugural lecture about the future of applied mathematics. It was delivered in 2006 in Leicester, UK. I analysed the change of era in science, the main locomotive problems and tried to explain the reasons of "Unreasonable Effectiveness of Mathematics".
Differences between Classical and Quantum Probability.
Quantum probability provides a general framework to explain paradoxical findings that cannot be explained through classical probability theory.
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.
81st ICREA Colloquium "Two Perspectives on the Relation between Philosophy an...Mayi Suárez
Casal and Sturm present two different ways in which philosophy relates to science. Sturm begins by sketching “philosophical naturalism”, a view that tries to answer philosophical questions employing methods and data from the empirical sciences. He then analyses the ongoing debate between the “heuristics and biases” approach and the “bounded rationality” program in order to assess the potential of naturalizing rationality, and its limits. Casal turns to ethics. Ethics is a branch of philosophy usually divided in three levels: metaethics, normative ethics and applied ethics. Casal focuses on the relevance of scientific findings, particularly in evolutionary biology, to major controversies in all these levels.
81st ICREA Colloquium "Two Perspectives on the Relation between Philosophy an...Mayi Suárez
Casal and Sturm present two different ways in which philosophy relates to science.
Sturm begins by sketching “philosophical naturalism”, a view that tries to answer philosophical questions employing methods and data from the empirical sciences. He then analyses the ongoing debate between the “heuristics and biases” approach and the “bounded rationality” program in order to assess the potential of naturalizing rationality, and its limits.
Dynamical Systems Modeling in NeuroscienceYohan John
A lecture I gave recently as an introduction to computational neuroscience.
Note: the "pentagon of science" was proposed by Eric L Schwartz, a professor at BU who coined the term "computational neuroscience".
My inaugural lecture about the future of applied mathematics. It was delivered in 2006 in Leicester, UK. I analysed the change of era in science, the main locomotive problems and tried to explain the reasons of "Unreasonable Effectiveness of Mathematics".
Differences between Classical and Quantum Probability.
Quantum probability provides a general framework to explain paradoxical findings that cannot be explained through classical probability theory.
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.
81st ICREA Colloquium "Two Perspectives on the Relation between Philosophy an...Mayi Suárez
Casal and Sturm present two different ways in which philosophy relates to science. Sturm begins by sketching “philosophical naturalism”, a view that tries to answer philosophical questions employing methods and data from the empirical sciences. He then analyses the ongoing debate between the “heuristics and biases” approach and the “bounded rationality” program in order to assess the potential of naturalizing rationality, and its limits. Casal turns to ethics. Ethics is a branch of philosophy usually divided in three levels: metaethics, normative ethics and applied ethics. Casal focuses on the relevance of scientific findings, particularly in evolutionary biology, to major controversies in all these levels.
81st ICREA Colloquium "Two Perspectives on the Relation between Philosophy an...Mayi Suárez
Casal and Sturm present two different ways in which philosophy relates to science.
Sturm begins by sketching “philosophical naturalism”, a view that tries to answer philosophical questions employing methods and data from the empirical sciences. He then analyses the ongoing debate between the “heuristics and biases” approach and the “bounded rationality” program in order to assess the potential of naturalizing rationality, and its limits.
What can and cannot be said about randomness using quantum physics acínMayi Suárez
It is usually said that quantum physics is, contrary to classical physics, intrinsically random. The intrinsic randomness of quantum physics follows from the fact that it is possible to observe correlations among quantum particles for which there exists no classical and deterministic model. The observation of these correlations, however, requires some assumptions about the setup. In particular, it requires some initial randomness, which makes the whole argument apparently circular.
We discuss how it is possible to relax this circularity and conclude that an intrinsic form of randomness with no classical analogue does exist in the quantum world.
Proteins adopt beautiful shapes that enable them to perform an incredible array of tasks. But these wiggly little creatures cannot stay still. Is this a nuisance or a blessing?
Xavier Salvatella discusses where the limit is: can proteins be completely disorganised? Can we study and understand intrinsically disordered proteins from a structural point of view? How can this class proteins perform functions if they have no structure? Why have they evolved? Is it ever going to be possible to modify the function of this class of proteins with small molecules, as we have learned to do with proteins that fold?
71st ICREA Colloquium - The unbearable lightness of being (a protein) by Xavi...Mayi Suárez
Proteins adopt beautiful shapes that enable them to perform an incredible array of tasks. But these wiggly little creatures cannot stay still. Is this a nuisance or a blessing?
After a basic introduction to proteins, Xavier Barril focuses on the implications of protein flexibility for drug discovery. Showing that a rigid representation has been, and continues to be, extremely useful. He presents some of the failures and challenges in introducing a more realistic view, but also how the dynamic perspective is gaining ground thanks to the advances in structural biology and computational chemistry.
70th ICREA Colloquium - "What would Karl say? Two ICREA professors engage wit...Mayi Suárez
ICREA Research Professor David Block argues that a Marxist framing of issues related to language in society can lead to understandings of how the use of language and other semiotic modes is embedded in ongoing political, economic, social and cultural processes, showing how class struggle and class warfare are both materially and discursively constructed.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
insect taxonomy importance systematics and classification
Intrinsic randomness - Carl Hoefer
1. Objective chance and quantum
randomness
Carl Hoefer
ICREA - U. Barcelona
Sept. 27, 2016
1
2. Philosophers of science:
1. Try to understand the notion of law of nature or physical
law.
2. Try to understand the notions of objective or intrinsic
randomness, and objective chance.
Physicists are often curious about these topics too!
2
3. Goals of [the long version of ] this talk:
1. Explore the notion of an (irreducible, fundamental)
probabilistic law of nature, and argue that we don’t have a
good grasp of what it means to postulate such a thing.
Valerio Scarani: “What does it mean, a physical law that
has statistical character?”
A. Einstein: “Der Gott würfelt nicht.”
3
4. Goals of this talk:
1. Explore the notion of an (irreducible, fundamental)
probabilistic law of nature, and argue that we don’t have a
good grasp of what it would mean to postulate such a
thing.
2. Show that, by contrast, a probabilistic law that is grounded
on underlying determinism can be grasped easily - and we
have many good examples of such laws.
3. Offer some comments on how the randomness found in
quantum mechanics could be of this variety.
4
5. Objective probabilities or ‘chances’
• Pr(Heads) = 0.5, flipping a ‘fair’ coin
• Pr(00) in throw of 38-slot roulette wheel = 1/38
• Pr(Pu241 decay in 1 year) = 0.05
• Pr(spin-z up | spin-x up earlier) = 0.5
– ... what kind of facts are these?
– Can we make sense of them as objec*ve and ground-level
truths?
5
6. De Finetti on ‘probability’:
“My thesis, paradoxically, and a little provocatively, but
nonetheless genuinely, is simply this:
PROBABILITY DOES NOT EXIST
The abandonment of superstitious beliefs about the
existence of the Phlogiston, the Cosmic Ether, Absolute
Space and Time, . . . or Fairies and Witches was an
essential step along the road to scientific thinking.
Probability, too, if regarded as something endowed with
some kind of objective existence, is no less a misleading
misconception, an illusory attempt to exteriorize or
materialize our true probabilistic beliefs.”
• (But we must leave this topic to one side for now.)
6
7. Distinctions and notations
• indeterminism = ¬ determinism
• indeterminism vs random behavior
• indeterminism vs probabilistic (or ‘stochastic’) laws
7
8. Non-random indeterminisms
• Classical Mechanics (CM):
–Space Invaders (5-particle system in t-reverse)
–Norton’s Dome (& other symmetry-breaking situations)
8
9. Non-random indeterminisms
• General Relativity (GR):
–Naked singularities (e.g. “white holes”)
–Other types of ‘hole’
–models with no Cauchy surface
• What all these CM and GR cases have in common:
• No involvement of probability; indeterminism = simple breakdown of
determinism.
9
10. Distinctions and notations
• indeterminism = ¬ determinism
• indeterminism vs random behavior
• indeterminism vs probabilistic laws
• randomness in general vs probabilistic-law-randomness
–examples: cancer incidence, vs radioacCve decay rate
10
11. Distinctions and notations
• indeterminism = ¬ determinism
• indeterminism vs random behavior
• indeterminism vs probabilistic laws
• randomness in general vs probabilistic-law-randomness
–examples: cancer incidence, vs radioacCve decay rate
• product randomness vs process randomness
–[apparent randomness vs intrinsic randomness]
11
12. Distinctions and notations
• indeterminism = ¬ determinism
• indeterminism vs random behavior
• indeterminism vs probabilistic laws
• randomness in general vs probabilistic-law-randomness
–examples: cancer incidence, vs radioacCve decay rate
• product randomness vs process randomness
–[apparent randomness vs intrinsic randomness]
12
13. Outline:
I. The dialectics of primitive chance laws.
II. Chances from underlying determinism
III. QM & intrinsic randomness
13
14. Outline:
I. The dialectics of primitive chance laws.
II. Chances from underlying determinism
III. QM & intrinsic randomness
14
25. Bohmian Mechanics
• QM represents physical
systems with a
‘wavefunction’, Ψ.
• Basic idea of BM: In addition
to Ψ, there are in fact point-
like particles with well-
defined positions at all
times, moving on continuous
paths. Ψ acts on the
particles like a ‘pilot wave’,
determining their velocities
at every moment.
25
28. A theory with some appeal …
“Is it not clear from the smallness of the scintillation on the
screen that we have to do with a particle? And is it not clear,
from the diffraction and interference patterns, that the motion
of the particle is directed by a wave? De Broglie showed in
detail how the motion of a particle, passing through just one
of two holes in screen, could be influenced by waves
propagating through both holes. And so influenced that the
particle does not go where the waves cancel out, but is
attracted to where they cooperate. This idea seems to me so
natural and simple, to resolve the wave-particle dilemma in
such a clear and ordinary way, that it is a great mystery to me
that it was so generally ignored.” (J. Bell 1986)
28
30. Bohmian mechanics
1. Characterization of state:
(Ψ, X)
2. Schrödinger’s evolution:
3. The guidance equation (GE):
– If the wave funcCon is wriNen in polar form , the guidance equaCon
simply reads .
4. The statistical postulate:
30
≡ … ∈
Ψ … ∈
! ! !
"
! ! !
"
3
1 2 N
3
1 2
X (X , X , , X )
( , x , , ; )
N
N
Nx x t
t
∂Ψ
= Ψ
∂
ˆHih
∇ Ψ
= =
Ψ
!""" #
v Im
kk
k
k
dx
dt m
ρ = Ψ
2
0 0( , ) (x, )x t t
Ψ = !/iS
Re
= ∇
!""
m v Skk k
31. Bohmian mechanics
• The Bohmian particles follow trajectories in 3d-
space according to the so-called Guidance
equation:
(GE)
31
∇ Ψ
= =
Ψ
!""" #
v Im
kk
k
k
dx
dt m
32. Bohmian mechanics
• BM makes probabilistic predictions because of the
‘Quantum Equilibrium’ or Statistical Postulate:
(SP)
32
ρ = Ψ
2
0 0( , ) (x, )x t t
33. QM & intrinsic randomness. . .
What about Bohmian Mechanics??
• In order to say we have certified randomness from
quantum phenomena, we have to rule out BM and
similar Det hidden variable theories. . . How?
• Usual complaints made against BM:
• BM requires conspiratorial iniCal condiCons
• BM does not allow ‘free choice’ of A, B
• BM allows faster-than-light signalling
33
34. QM & intrinsic randomness. . .
What about Bohmian Mechanics?
• But these complaints are misguided:
• BM involves no conspiratorial super-determinism
• BM allows free choice of measurement se[ngs in Bell
experiments
• BM is a no-signalling theory
– . . . so the standard reasons for excluding ‘hidden
variable’ theories, like BM, seem ineffecCve.
34
35. QM & intrinsic randomness. . .
What about Bohmian Mechanics??
• BM allows free choice of measurement se[ngs in Bell
experiments
35
36. Causal structure (assumed) of EPR-
type experiments
36
• A, B: settings for
measurement device
• X, Y: spin/polarization
measurements (spacelike
separation between A, X
and B, Y).
• Z: pre-existing states able to
causally influence A, X, B
and Y.
A B
X Y
Z
E F
37. Causal structure of EPR experiments
(for Bohmians)
37
• Determination of A, B
partly or fully affected by
external factors E, F.
• Red arrows: non-local
causal influence, a
feature of Bohmian
mechanics.
A B
X Y
Z
E F
38. Causal structure of EPRB experiments
(for Bohmians)
38
• Determination of A, B
can be by human agents’
free choices;
• Or from photons from
opposite sides of the
galaxy if you like.
• No ‘conspiratorial
conditions’ needed for
deterministic story.
A B
X Y
Z
E F
39. QM & intrinsic randomness. . .
What about Bohmian Mechanics??
• Conspiracy (in the sense commonly invoked in the Bell Test
field) not needed. Non-local action at a distance is all that is
required to explain violation of Bell inequality.
• Experimenter ‘free choice’ perfectly OK (unless you think
determinism rules out free choice tout court)
39
40. . . . and what about signalling?
40
• BM is a “parameter
dependent” theory.
• Parameter dependence ≠
effective signalling
• Statistical postulate
ensures no effective
signalling possible
• SP ≠ conspiratorial initial
conditions in the
“superdeterminism” sense.
A B
X Y
Z
E F
41. Important note: I am not endorsing
Bohm’s theory
• There are reasons to be skeptical that BM is on the right
track.
• But - violation of no-signalling (at the surface level,
where we have reason to trust N-S), or of free choice,
are not among those reasons
• Plus: where there’s one theory, there may be more out
there waiting to be discovered.
41
42. Contrast: properties of standard QM
• Non-local
• Contextual
• Parameter-dependence [Copenhagen]
• [arguable] causation at spacelike separation
42
43. Summing up
1. I argued that it’s difficult to spell out what we mean when we postulate
intrinsic randomness of the propensity or chance-law variety.
2. By contrast, I argued, we can understand objective probability claims
if they arise from determinism + nicely-distributed initial conditions.
– Quantum “randomness” in Bohmian Mechanics is of exactly this sort.
3. I noted that while Bohmian QM has no intrinsic randomness (being
deterministic), it satisfies no-signalling in a pragmatic or effective
sense. At the surface, it’s a counterexample to randomness-
certification arguments; but at the deep level one could say it is a
“signalling” theory. But in this deep-level sense, we have no way to
rule out that nature herself is signalling.
4. Distinction: certified [intrinsic] randomness vs certified [effective]
randomness. BM is counterexample to former, but not the latter.
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