Questions tagged [research-level]

The research-level tag applies to questions that arise in graduate and post-secondary work. These questions often require domain-specific knowledge and could not be answered from a general source or may be beyond the level typically covered by Wikipedia and other popular sources. Research-level questions should not require new or groundbreaking research and results to answer.

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Photon number autocorrelation in Cavity QED

I am studying this paper dealing with optomechanical strong coupling, and I don't understand one very relevant part of it. In particular, the authors define (equation (8)) a photon number ...
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3 votes
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+50

Question about field configurations on the boundary of $\mathcal{I}^+$

I am reading Strominger's lecture notes "The infrared structure of gravity and gauge theory" (https://arxiv.org/abs/1703.05448). In chapter two, while trying to derive an expression about ...
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Faddeev - Kulish paper questions

I have several questions regarding the paper Asymptotic conditions and infrared divergences in QED, written by Faddeev and Kulish in 1970. This is not a post about one question, but since all the ...
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3 votes
0 answers
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Subleading soft theorem and gauge invariance

I am reading a paper by Burnett-Norman and Kroll, called extension of the Low soft photon theorem (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.20.86). The authors claim that in order to ...
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Did the founders of the string theory "made a measurement in the history of the physics? [closed]

The paper "BOUNDARY CONDITIONS, FUSION RULES AND THE VERLINDE FORMULA" by John L. Cardy mentioned that This description is somewhat heuristic, however, because the holomorphic part of a ...
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4 votes
2 answers
145 views

String theory hilbert space - Gas of free gravitons

I am trying to understand the arguments given in MAGOO in chapter 3.4.1(Hilbert Space of String Theory). The authors give descriptions of the Hilbert space of String Theory when we consider our theory ...
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5 votes
1 answer
65 views

Conserved charge at null infinity associated with Large gauge transformation

I am reading Strominger's lecture notes "Lectures on the infrared structure of gravity and gauge theory" (https://arxiv.org/abs/1703.05448). At some point, following (I guess) the authors of ...
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Entropy Calculation from Regularized Hamiltonian

I refer to Srednicki's 'Entropy and Area' paper here.I want to derive the expression for entropy (20), given by $$S_{l}(n,N) = \xi_{l}(n)[-\log\xi_{l}(n) + 1], \xi_{l}(n) = \frac{n(n+1)(2n+1)^{2}}{64l^...
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1 vote
1 answer
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Momentum integral yielding $\delta$ function

I am reading the paper Asymptotic conditions and infrared divergences in quantum electrodynamics by P. P. Kulish & L. D. Faddeev (the paper is not important for the question I think, but I will ...
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What subfields, or specific works/articles, would cover the "the physics of ropes"?

Undergraduate student here. Yes, this is very similar to a post I made a year ago, however, as this topic is now pertinent to the research I plan to undertake, and now that I have distilled the idea a ...
1 vote
1 answer
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Faddeev-Kulish Asymptotic Dynamics Question

I am reading a paper by Faddeev and Kulish ("Asymptotic conditions and infrared divergences in QED" written in 1970) and I have a question regarding the nonrelativistic problem of Coulomb ...
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  • 467
1 vote
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An Exotic Transport Phenomena with Zero-Current at Different Voltage Values

I am a researcher working with active matters, and in one of my experiment I've seen a very exotic transport phenomena which we obtain zero-current for many different values of voltage (those values ...
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1 vote
0 answers
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How to apply the boundary condition in the derivation of the 2-point function in MAGOO?

In the famous AdS/CFT review, in section 3.3.1 the authors give the two-point function of the operator $\mathcal{O}$ for which $\phi_0$ is a source, we write $$ \langle\mathcal{O}(p)\mathcal{O}(q)\...
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1 vote
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38 views

Momentum Conserving Delta Function and Soft Gravitons

I am reading a paper called "Testing subleading multiple soft graviton theorem for CHY prescription" written by Subhroneel Chakrabarti, Sitender Pratap Kashyap, Biswajit Sahoo, Ashoke Sena ...
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4 votes
1 answer
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In Quantum Field Theory in Curved Spacetime, are particle states energy eigenstates?

I've been reading the paper Particle and energy cost of entanglement of Hawking radiation with the final vacuum state, by R. M. Wald (arXiv: 1908.06363 [gr-qc], DOI: 10.1103/PhysRevD.100.065019). It ...
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3 votes
0 answers
84 views

QED Soft Theorems and Momentum Conserving $\delta$ function

The sub-leading soft theorem (or Low theorem) states that the radiative Feynman amplitude is associated to the non-radiative Feynman amplitude in the following way $$\mathcal{M}_{\text{rad}}(\omega_k,\...
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2 votes
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There is any kind of research on the use of a "Light-Gas Gun" on the production of Metallic Hydrogen?

Well, if it was that simple, there would already be some research on it, but I couldn't find any. Light-Gas Gun: If you don't know, a Light-Gas Gun is basically an apparatus that is able to shot ...
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3 votes
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Restoration of symmetry explicitly broken by anomaly

What is the meaning of the restoration at finite temperature of a symmetry that is "broken" by the presence of an anomaly. If the symmetry is not there why is it restored at finite ...
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2 votes
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Symmetry group of QCD

In "Remarks on the chiral phase transition in chromodynamics" (1984) by Pisarski and Wilczek it is stated that the (classical) global flavor symmetry is $SU(2)\times SU(2) \times U_A(1)$ ...
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1 vote
1 answer
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Transformations generated by asymptotic Killing vectors

I want to know how tensors transform under the transformations generated by Killing vectors. In particular I am interested in asymptotic symmetries and asymptotic Killing vectors. In order to ...
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3 votes
0 answers
65 views

Question regarding the asymptotic values of out-of-time order correlators (OTOCs)

Quoting A bound on chaos by Maldacena, Shenker and Stanford: Strong chaos, the butterfly effect, is a ubiquitous phenomenon in physical systems, explaining thermal behavior, among other things. In ...
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What research has been done to develop a theory of ideal fluids?

A prof mentioned that there has been a lot of research to develop a theory of ideal fluids. A subsequent literature search wasn't very illuminating. Could somebody please tell me what has been done on ...
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2 votes
0 answers
106 views

Resources to start research on the SYK model, with AdS/CFT in mind

What are the main resources to learn the SYK model, focusing more on the AdS/CFT side rather than pure condensed matter theory, assuming a comfortable background in QFT, GR, and a bit of bosonic ...
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Scaling of Precision in Measurements as inverse of square root of Mass of Objects involved

I am currently reading this article: Direct observation of deterministic macroscopic entanglement https://science.sciencemag.org/content/372/6542/622 The line that I am referring to is in the second ...
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1 vote
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How does the Kalmeyer-Laughlin argument work?

I want to ask about the argument in the Kalmeyer-Laughlin paper that connects the Heisenberg Hamiltonian to a quantum Hall one. I know there is a related question about the same paper. My question is ...
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1 vote
1 answer
67 views

Why are maximally entangled continuous variable states not physical?

I have been going through this paper: https://arxiv.org/abs/quant-ph/9908056 There in, just after eq (1), it's mentioned that maximally entangled continuous variable states are not physical. Why is ...
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3 votes
2 answers
101 views

Boltzmann Law in moving fluids?

In my research, I am concerned with the analysis of systems which operate essential like this: There is a tube, say of radius $r$. In this simplification in can be infinitely long. Air moves along it ...
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1 vote
0 answers
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’t Hooft 1982 Phys. Scr. 25 133 on superconductivity

In G. ’t Hooft 1982 Phys. Scr. 25 133 paper 'The Topological Mechanism for Permanent Quark Confinement in a Non-Abelian Gauge Theory' He wrote in the abstract: We first argue that indeed ...
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1 vote
1 answer
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What is an automated vent valve?

I was inquiring a company about an air-cooled turbo-molecular pump, and the company asked me whether I used an automated vent valve. What does automated vent valve mean and do? How does it relate to ...
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2 votes
2 answers
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What does 3D buckling reconstruction mean?

In condensed matter/material science papers, I often encountered phrases like structural reconstruction, 3D reconstruction, 3D buckling reconstruction, etc. What do these phrases mean (especially the ...
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0 votes
1 answer
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Is there any specific template to write a discovery paper? How to write a paper then? [closed]

I am really an enthusiast of physics! I like to write, read and even live with physics! but the question comes how could I express my researches? I am an amateur physicist but don't really know how to ...
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3 votes
0 answers
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Classification of 10-dimensional heterotic string theories

In many textbooks the typical story is told that there are exactly 2 possible heterotic theories in 10 dimensions, the $E8\times E8$ as well as the $SO(32)$ theories. This is of course only true for ...
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2 answers
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Can a self-educated physicist publish papers? [closed]

I started self learning mathematics and physics .. but the thing is I can't join a college , but I watch online lectures and read textbooks instead .. I am interested in theoritical physics .. But I ...
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16 votes
2 answers
446 views

Is the recent Nature paper by Minev et al. evidence of new physics?

Ok the title might be slightly clickbaity. A better one might be "Why isn't the recent Nature paper by Minev et al. evidence of new physics?", but I didn't want to make too many assumptions ...
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3 votes
0 answers
60 views

Regular black hole with an evanescent horizon

I'm reading a great paper named Geodesically Complete Black Holes by R. Carballo, F. Filippo, S. Liberati and M. Visser about regular black holes and I'm trying to understand a particular situation. ...
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1 vote
0 answers
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Why is the entry barrier in Physics Research Topics so high? [closed]

Why is the entry barrier in physics research so high?? When I try to read a research paper to see the latest developments in a particular topics I am always held back by my mathematical abilities. And ...
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1 vote
0 answers
118 views

Non-markovian random walk. Elephant random walk

When one does the numerics for the usual random walk, one might use the transition matrix in order to get the probability ar time $t$ of the process. As expected, the asymptotic behavior yields a ...
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0 votes
1 answer
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What's the index (or topological charge) of this vector field image?

I am doing some research in a condensed matter system, and found this Berry curvature / vector field configuration that is unusual. I cannot find another example of something similar, either from ...
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0 votes
0 answers
77 views

QCD methods - Dirac trace, trace in color space, trace in flavor space

What is meant by the following terms in QCD - Dirac trace, trace in color space, trace in flavor space, etc. Could someone explain with an example (For eg. what's the diffrerence between something ...
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1 vote
1 answer
192 views

How to transform a given Lagrangian to a Nambu-Gorkov basis?

With reference to the Nambu (or famously, Nambu-Gorkov) transformation in this paper, could someone explain the reason behind using the 3rd Pauli matrix in the Lagrangian after equation (2.3) (would ...
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6 votes
0 answers
107 views

Are Chern-Simons theories classified by bordism groups?

For a long time it was thought that anomalies for a group $G$ were classified by $H^n(BG)$, although it is now understood that they are in fact classified by $\Omega^n(BG)$. On the other hand, ...
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0 votes
1 answer
56 views

Waves on a topological surface

Are there any formulas for wave motion on a topological surface, like a Mobius strip? If not, is this a valid opportunity for research?
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5 votes
1 answer
111 views

Geometric representations of affine Lie algebras

I have recently been reading literature on geometric constructions of representations of affine Lie algebras by Nakajima and others. In particular, the representations arise as cohomologies of moduli ...
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0 votes
1 answer
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Deriving Drude Theory from Plasma Fluid Equations

Does anyone have experience in looking at Drude theory from the perspective of plasma physics instead of the standard, condensed-matter, "electrons in a metal" sort of thing and can point ...
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5 votes
1 answer
246 views

Definition for long range entanglement (LRE) by generalized local unitary (gLU) and generalized stochastic local (gSL) transformations

I am studying this book: Quantum Information Meets Quantum Matter -- From Quantum Entanglement to Topological Phase in Many-Body Systems (https://arxiv.org/abs/1508.02595). In chapter 7, it introduces ...
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0 votes
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Photon rate definition in input-output formalism: why such definition commonly used?

I consider a one dimensional waveguide. I study free field propagation on it. I apply periodic boundary condition with periodization length $L$ to describe the physics with Fourier series and not ...
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0 votes
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How to get algebraic PSG solutions once we got the constraints?

The question is more technical than conceptual. I've been trying to understand the classification of spin liquids as done by Prof.Wen. I have got the constraints on IGG(Invariant gauge group) elements ...
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2 votes
1 answer
218 views

Input-output theory: interpretation of the final expression

I am trying to understand this paper- https://journals.aps.org/pra/abstract/10.1103/PhysRevA.30.1386 I will try to give my understanding of the paper first. We start with the quantum Langevin ...
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  • 149
2 votes
1 answer
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Metal-insulator transition a quantum phase transition?

One can consider two main types of metal-insulator transitions (MIT), nl. interaction-driven (Mott) or disorder-driven (Anderson-Mott). Recently, I have been reading that these MIT might also have ...
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  • 671
3 votes
1 answer
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Constructing W-algebras

I am following the algorithm in W-algebras with two and three generators, in order to construct consistent (anti-)commutator relations for a particular W-algebra. I am considering $W(2,4,4)$ where ...
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