Heterostructures, HBTs and Thyristors : Exploring the "different"Shuvan Prashant
This presentation aims at presenting the concepts of heterostructures : a structure resulting from semiconductors of different band gaps are used to form junctions. These junctions could have interesting effects due the potentials formed by the bands at the interfaces.
On this presentation i describe all the features and types of diode. This presentation started from short but understandable history of diode or zener . How diode is working? Answer of this question also clear after read all this presentation.
Here This is the different between Smart and digital Transformer.And the definition of Smart transformer that may helpful for Student for nice presentation.
Heterostructures, HBTs and Thyristors : Exploring the "different"Shuvan Prashant
This presentation aims at presenting the concepts of heterostructures : a structure resulting from semiconductors of different band gaps are used to form junctions. These junctions could have interesting effects due the potentials formed by the bands at the interfaces.
On this presentation i describe all the features and types of diode. This presentation started from short but understandable history of diode or zener . How diode is working? Answer of this question also clear after read all this presentation.
Here This is the different between Smart and digital Transformer.And the definition of Smart transformer that may helpful for Student for nice presentation.
Phase transition and the Casimir effect are studied in the complex scalar field with one spatial dimension to be compactified. It is shown that the phase transition is of the second order and the Casimir effect behaves quite differently
depending on whether it’s under periodic or anti-periodic boundary conditions
A model of electron pairing, with depletion of mediating phonons at fermi sur...Qiang LI
We present a model of electron pairing based on nonstationary interpretation of electron-lattice interaction. Electron-lattice system has an intrinsic time dependent characteristic as featured by Golden Rule, by which electrons on matched pairing states are tuned to lattice wave modes, with pairing competition happening among multiple pairings associated with one electron state. The threshold phonon of an electron pair having a good quality factor can become redundant and be released from the pair to produce a binding energy. Lattice modes falling in a common linewidth compete with one another, like modes competing in a lasing system. In cuprates, due to near-parallel band splitting at and near Fermi Surface (EF), a great number of electron pairs are tuned to a relatively small number of lattice wave modes, leading to strong mode competition, transfer of real pairing-mediating phonons from EF towards the “kink”, and depletion of these phonons at and near EF.
phonon as carrier of electromagnetic interaction between lattice wave modes a...Qiang LI
The new results reported here mainly include: 1) recognition that phonon is carrier of electromagnetic interaction between its lattice wave mode and electrons; 2) recognition that binding energy of electron pairs of high-temperature superconductivity is due to escape of optical threshold phonons, of electron pairs at or near Fermi level, from crystal by direct radiation; 3) recognition that binding energy of electron pairs of low-temperature superconductivity is possibly due to escape of non-optical threshold phonons by anharmonic crystal interactions; and, 4) recognition of a possible mechanism explaining why some crystals never have a superconducting phase. While electron pairing is phonon-mediated in general, HTS should be associated with electron pairing mediated by optical phonon at or near Fermi level (EF), so the rarity of HTS corresponds to the rarity of such pairing match.
phonon as carrier of electromagnetic interaction between lattice wave modes a...Qiang LI
The new results reported here mainly include: 1) recognition that phonon is carrier of electromagnetic interaction between its lattice wave mode and electrons; 2) recognition that binding energy of electron pairs of high-temperature superconductivity is due to escape of optical threshold phonons, of electron pairs at or near Fermi level, from crystal by direct radiation; 3) recognition that binding energy of electron pairs of low-temperature superconductivity is possibly due to escape of non-optical threshold phonons by anharmonic crystal interactions; and, 4) recognition of a possible mechanism explaining why some crystals never have a superconducting phase. While electron pairing is phonon-mediated in general, HTS should be associated with electron pairing mediated by optical phonon at or near Fermi level (EF), so the rarity of HTS corresponds to the rarity of such pairing match.
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A Mechanism Of Electron Pairing Relating To SupperconductivityQiang LI
Mechanism of superconductivity is based on a mechanism of electron pairing near EF with definite binding energy. A candidate mechanism of such electron pairing is described in this paper. Electron pairs are induced by EM wave modes generated by corresponding lattice wave modes. The pairs are formed between E(k) faces from different Brillouin zones, with definite binding energies. The binding energy of an electron pair is characterized by the frequency of the EM mode that induces the pairing.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
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.
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What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
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.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Unveiling the Energy Potential of Marshmallow Deposits.pdf
feynman
1. P780.02 Spring
2003 L3
Richard KassFeynman Diagrams
Feynman diagrams are pictorial representations of
AMPLTUDES of particle reactions, i.e scatterings or
decays. Use of Feynman diagrams can greatly reduce the
amount of computation involved in calculating a rate or
cross section of a physical process, e.g.
muon decay: µ−
→e-
νeνµ or e+
e-
→ µ+
µ-
scattering.
Like electrical circuit diagrams, every line in the diagram has a strict
mathematical interpretation. Unfortunately the mathematical overhead necessary
to do complete calculations with this technique is large and there is not enough
time in this course to go through all the details. The details of Feynman diagrams
are addressed in Advanced Quantum and/or 880.02. For a taste and summary of
the rules look at Griffiths (e.g. sections 6.3, 6.6, and 7.5) or Relativistic Quantum
Mechanics by Bjorken & Drell.
Feynman and his diagrams
2. P780.02 Spring
2003 L3
Richard Kass
Feynman Diagrams
Each Feynman diagram represents an AMPLITUDE (M).
Quantities such as cross sections and decay rates (lifetimes) are proportional to |M|2
.
The transition rate for a process can be calculated using time dependent perturbation
theory using Fermi’s Golden Rule:
qf=final state momentum
vf= speed of final state particle
vi= speed of initial state particle
)(||
2 2
spacephaseMratetransition ×=
π
The differential cross section for two body scattering (e.g. pp→pp) in the CM frame is:
2
2
2
||
4
1
M
vv
q
d
d
fi
f
π
=
Ω
σ
The decay rate (Γ) for a two body decay (e.g. K0
→ π+
π-
) in CM is given by:
M&S B.29, p296
2
2
||
8
||
M
cm
pS
π
=ΓGriffiths 6.32 m=mass of parent
p=momentum of decay particle
S=statistical factor (fermions/bosons)
In most cases |M|2
cannot be calculated exactly.
Often M is expanded in a power series.
Feynman diagrams represent terms in the series expansion of M.
In lowest order perturbation
theory M is the fourier transform
of the potential. M&S B.20-22, p295
“Born Approximation” M&S 1.27, p17
3. P780.02 Spring
2003 L3
Richard KassFeynman Diagrams
Feynman diagrams plot time vs space:
time
space initial state final state
e-
e-
e-
e-
Moller Scattering e-
e-
→e-
e-
OR
time
space
initial state
final state
M&S
style QED Rules
Solid lines are charged fermions
electrons or positrons (spinor wavefunctions)
Wavy (or dashed) lines are photons
Arrow on solid line signifies e-
or e+
e-
arrow in same direction as time
e+
arrow opposite direction as time
At each vertex there is a coupling constant
√α, α= 1/137=fine structure constant
Quantum numbers are conserved at a vertex
e.g. electric charge, lepton number
“Virtual” Particles do not conserve E, p
virtual particles are internal to diagram(s)
for γ’s: E2
-p2
≠0 (off “mass shell”)
in all calculations we integrate over the virtual
particles 4-momentum (4d integral)
Photons couple to electric charge
no photons only vertices
4. P780.02 Spring
2003 L3
Richard Kass
Feynman Diagrams
We classify diagrams by the order of the coupling constant:
Bhabha scattering: e+
e-
→e+
e-
Amplitude is of order α.
Amplitude is of order α2
.
Since αQED =1/137 higher order diagrams should be corrections
to lower order diagrams.
This is just perturbation Theory!!
This expansion in the coupling constant works for QED since αQED =1/137
Does not work well for QCD where αQCD ≈1
α1/2
α1/2
α1/2
α1/2
α1/2
α1/2
5. P780.02 Spring
2003 L3
Richard Kass
Feynman Diagrams
For a given order of the coupling constant there can be many diagrams
Bhabha scattering: e+
e-
→e+
e-
Must add/subtract diagram together to get the total amplitude
total amplitude must reflect the symmetry of the process
e+
e-
→γγ identical bosons in final state, amplitude symmetric under exchange of γ1, γ2.
e+
e-
γ1
γ2 e+
e- γ1
γ2
+
Moller scattering: e-
e-
→e-
e-
identical fermions in initial and final state
amplitude anti-symmetric under exchange of (1,2) and (a,b)
e-
1 e-
a
e-
be-
2
e-
1 e-
b
e-
ae-
2
-
amplitudes can
interfere constructively
or destructively
6. P780.02 Spring
2003 L3
Richard Kass
Feynman Diagrams
Feynman diagrams of a given order are related to each other!
e+
e-
→γγ
γγ→e+
e-
compton scattering
γ e-
→γ e-
electron and positron
wavefunctions are related
to each other.
γ’s in final state
γ’s in inital state
7. P780.02 Spring
2003 L3
Richard KassAnomalous Magnetic Moment
The electron's anomalous magnetic moment (ae
) is now known to 4 parts per billion.
Current theoretical limit is due to 4th order corrections (>100 10-dimensional integrals)
The muons's anomalous magnetic moment (aµ
) is known to 1.3 parts per million.
(recent screwup with sign convention on theoretical a calculations caused a stir!)
Calculation of Anomalous Magnetic Moment
of electron is one of the great triumphs of QED.
In Dirac’s theory a point like spin 1/2 object of electric
charge q and mass m has a magnetic moment: µ=qS/m.
In 1948 Schwinger calculated the first-order radiative correction
to the naïve Dirac magnetic moment of the electron.
The radiation and re-absorption of a single virtual photon,
contributes an anomalous magnetic moment of ae
= α/2π ≈ 0.00116.
Dirac MM modified to: µ=g(qS/m) and
deviation from Dirac-ness is: ae
≡ (ge
- 2) / 2
Basic interaction
with B field photon
First order correction
3rd order corrections