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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37 views

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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12answers
13k views

What is spontaneous symmetry breaking in quantum systems?

Most descriptions of spontaneous symmetry breaking, even for spontaneous symmetry breaking in quantum systems, actually only give a classical picture. According to the classical picture, spontaneous ...
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0answers
57 views

’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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1answer
186 views

Schwarzschild radius in matrix models

The Schwarzschild radius for 11D BHs is given by $l_{11}(l_{11}m)^{1/8}$, which is the special case ($D=11$) of the general dimensional case of $(G_Dm)^{\frac{1}{D-3}}$. Here $m$ is the BH mass and $...
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1answer
24 views

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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0answers
14 views

Angular Velocity of Horizontal Pendulum in all 6-DOF for Lagrange EOM

I'm hoping to get some assistance on a topic I (and it seems like many people) struggle with, namely the angular velocity associated of an object oriented in 3D space. I'm an electrical engineer, so ...
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2answers
114 views

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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0answers
9 views

How (or where) to look up vapor pressure of a material at ultra-high vacuum pressure?

Is there a way to look up the vapor pressure of a given material (usually binary compounds or simply elements) at ultra-high vacuum (usually near $10^{-9}$ Torr). For example, if I want to know the ...
18
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1answer
1k views

Relation between cohomology and the BRST operator

Given a manifold $M$, we may define the $p$th de Rham cohomology group $H^p(M)$ as the quotient, $$C^p(M) \, / \, Z^p(M)$$ where $C^p$ and $Z^p$ are the groups of closed and exact $p$-forms ...
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27 views

BEC Relaxation to Dispersion Minimum

I am reading this paper, which looks at the emergence of a double well dispersion in an optical lattice through shaking as in the figure below. I am curious as to what mechanism results in the atoms ...
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1answer
48 views

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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How to use quartz crystal microbalance (QCM) to determine thin film growth time in molecular beam epitaxy (MBE)?

Let's put the question in the context of growing Bi2Se3 thin film. Say, we would like to grow 20 quintuple layers of Bi2Se3 using MBE. The flux rate of Bi dominates that of Se for the purpose of ...
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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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2answers
86 views

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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1answer
342 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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6k views

Linear sigma models and integrable systems

I'm a mathematician who recently became very interested in questions related to mathematical physics but somehow, I faced difficulties in penetrating the literature... I'd highly appreciate any help ...
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1answer
373 views

Truncation of $D=5$, ${\cal N}=8$ Supergravity by $\mathbb Z_2^3$

The scalar manifold of $D=5, \mathcal N=8$ SUGRA is $$\mathcal M = \frac{E_{6(6)}}{Usp(8)}$$ where $USp(8)$ is a maximal compact subgroup of $E_{6(6)}$ and the 42 scalars of the theory correspond ...
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1answer
182 views

Peskin's duality in XY model (Mandelstam-'t Hooft duality in abelian lattice models)

I am studying the old paper by Peskin (1978): Mandelstam-'t Hooft duality in abelian lattice models (https://doi.org/10.1016/0003-4916(78)90252-X). However, I am confused about some details of ...
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0answers
17 views

How to find length of object in photo, object at an angle

I have a picture of a section of a rectangular prism taken at an angle so that it isn't facing parallel with the camera like below. The end of the prism is cut off by the photo, and I have a scale for ...
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5answers
747 views

Connections and applications of SLE in physics

In probability theory, the Schramm–Loewner evolution, also known as stochastic Loewner evolution or SLE, is a conformally invariant stochastic process. It is a family of random planar curves that are ...
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1answer
178 views

How many times do solar protons repeatedly fuse and fission before they form deuteron

In the proton-proton chain reaction in the Sun, the first step is $$p + p \rightarrow \; ^2_2{\rm He} .$$ After this, the most likely thing to happen next is that the reverse reaction occurs: the $^...
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1answer
2k views

ADM Hamiltonian formalism and Quantum gravity

is there a Hamiltonian reformultion of gravity ?=? if so if we use the usual Quantization scheme we can not we quantizy the gravity ?? in terms of a Gauge Theory with the potential $ A_{\mu}^{i} $ ...
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0answers
446 views

Minimal strings and topological strings

In http://arxiv.org/abs/hep-th/0206255 Dijkgraaf and Vafa showed that the closed string partition function of the topological B-model on a Calabi-Yau of the form $uv-H(x,y)=0$ coincides with the free ...
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0answers
52 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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0answers
73 views

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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0answers
898 views

Dynamics of a bouncing capsule

I am working on a research project investigating the bounce of a capsule. I have tried to model it using conservation of energy, where we considered torque by normal force and friction during the ...
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0answers
62 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 ...
7
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1answer
332 views

What is known about Higgs LHC machine learning algorithm for identifying Higgs events?

Recently many LHC-affiliated organizations and otherwise announced the Higgs ML learning challenge (in May) running over the summer. There are many competing teams and significant results posted ...
5
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1answer
86 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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1answer
231 views

Allowed anyons for Chern-Simons at level $k.$

Ref.1. proves that the allowed representations of Chern-Simons $\mathrm{SU}(2)_k$ are those with dimension $$ \dim(R)\le k+1\tag{7.53} $$ Question: Is the generalisation of $(7.53)$ to arbitrary $N$ ...
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2answers
761 views

Lindblad and Input-Output Formalism in Quantum Optics

I'm confused about how to apply the Lindblad formalism and the input-output formalism in practice, and how one goes between the two. Suppose I have a cavity (C) coupled to a reservoir (R), with the ...
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0answers
19 views

Extended Blonder Tinkham Klapwijk in graphene

Background In this paper the author studies the BdG equation for a metal-superconductor-metal system. The left metal is electron doped and is in the region $x<0$, the supercondcutor is in the ...
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1answer
48 views

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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0answers
20 views

Calculating the Nambu-Gorkov propagator (given its inverse) for quarks

I am working through this paper on the calculation of a Nambu-Gorkov propagator, could someone explain how did we reach the next step right after equation (16)?
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1answer
1k views

Strong interacting v.s. Strong Coupling v.s. Strong Correlated

One of the active research areas in present is Strong interacting, Strong Coupling, Strong Correlated regime of the phases of matters. It seems to me that some physicists in the fields often mix the ...
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0answers
38 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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0answers
22 views

Calculating the quark propagator while dealing with the color, Dirac & flavor matrices all together

$S^+$ is a diagonal matrix in color space, and is given as : $S^+ = S_{rg} ^+ \hat{P_{rg}} + S_b ^+ \hat{P_b}, where, \hat{P_b} = 1_c - \hat{P_{rg}}$ is the projector on blue quarks, $\hat{P_{rg}}$ ...
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1answer
92 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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0answers
81 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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0answers
14 views

Inferring angle of source?

Given the relative distance of 3 radio antennae, I want to infer an incident angle for some radio source seen by all 3 antennae, which I know to be on the ground. All I know is the relative locations ...
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1answer
46 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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3answers
1k views

Renormalization Group for non-equilibrium

For equilibrium/ground state systems, a (Wilson) renormalization group transformation produces a series of systems (flow of Hamiltonians/couplings $H_{\Lambda}$ where $\Lambda$ is the cut-off) such ...
9
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1answer
258 views

What compactifications of the Poincaré group have been studied?

As we know, the Poincaré group is non-compact. Poincaré invariance has been observed at velocities and energies up to $10^{20}$ eV in cosmic rays. The other day, I was thinking about how the $SU(2)$ ...
4
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2answers
85 views

By how much are various dibaryon states unbound?

It has been known for a long time that the deuteron is stable but the dineutron (nn) and diproton (pp) are not. Many textbooks comment on this, but all the ones I found so far do not give quantitative ...
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1answer
82 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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1answer
50 views

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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2answers
4k views

Bogomol'nyi-Prasad-Sommerfield (BPS) states: Mathematical definition

What is the proper mathematical definition of BPS states? In string theory the BPS states correspond either to coherent sheaves or special Lagrangians of Calabi-Yau manifold depending upon the type of ...
9
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2answers
598 views

The $I_{3322}$ Inequality

I am trying to understand the $I_{3322}$ inequality which is an another example of Bell inequalities and which is different from the famous CHSH inequality. I haven't got hold of any standard ...
13
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1answer
2k views

String theory from a mathematical point of view

I have a great interest in the area of string theory, but since I am more focused on mathematics, I was wondering if there is any book out there that covers mathematical aspects of string theory. I ...
15
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2answers
5k views

The phrase “Trace Anomaly” seems to be used in two different ways. What's the relation between the two?

I've seen the phrase "Trace Anomaly" refer to two seemingly different concepts, though I assume they must be related in some way I'm not seeing. The first way I've seen it used is in the manner, for ...

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