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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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13 views

what is bolch optical mode?

I have read some papers(https://arxiv.org/ftp/arxiv/papers/1206/1206.4342.pdf) where the word ''bolch mode'' used. Now I want to know what kind of optical mode this is and how or why it is generated?
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1answer
105 views

What classifies gaugings?

Gauging a global symmetry $G$ introduces several free parameters to the theory. For example, In $d=4$, gauging a simple and simply-connected Lie group introduces a coupling constant and a theta term, ...
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0answers
17 views

Closest separable/ closest PPT state given an arbitrary state?

After searching for results, the closest result I found was https://aip.scitation.org/doi/pdf/10.1063/1.3591132?class=pdf. The summary of that paper is: Given an arbitrary seperable/PPT quantum state ...
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0answers
12 views

Comparision of using two dimensional mode or one dimensional in case of optical data transmission

Many works have been done to increase capacity of optical communication. I saw that some researcher using 1-D mode ,some 2-D to implement their device.The reson of using 1-d/2-d beacuse of their types ...
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1answer
14 views

What is the relationship of optical mode and data?

This question is on the plot of mode division multiplexing system where it is said capacity crunch can be solved using mdm technique. Now, we know single mode fiber can transmit upto 1Tbps. Now if i ...
1
vote
1answer
28 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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0answers
65 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 ...
8
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1answer
88 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
197 views

How does physics research work? [closed]

I am going to try and be as short and as concise as possible. I was thinking these last few days about how we're still trying to discover a unified Theory of Everything. The question is: how is this ...
0
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0answers
23 views

Maxwell-Chern-Simons equation: Translating from differential form to component form

I am trying to solve the scalar-coupled Maxwell-CS equations (which is one of the equation of motions in $N=2$ supergravity coupled to 3 vector multiplets), which is written in this form in the ...
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0answers
26 views

Vandermonde determinant factor in supersymmetric gauge localisation computation

I am trying to learn supersymmetric localisation computation in which the path integral of a supersymmetric gauge theory (placed on a sphere) can be localised exactly to a BPS configuration ...
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0answers
19 views

Loschmidt Amplitudes In Tight Binding Models

I am trying to understand the calculation in this paper which experimentally looks at dynamical phase transitions in a driven (shaken) haldene-like model. The definition of the Loschmidt Amplitude is ...
1
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0answers
50 views

How exactly does a spin TQFT depend on the spin structure?

Take a spin Chern-Simons TQFT, such as $U(N)$ or $SO(N)$ with odd level. Such system depends on the spin structure of the underlying manifold. But how exactly does the theory depend on the spin ...
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0answers
50 views

Can you do gauge theories over topological groups?

Quantum gauge theories involve (functional) integration over a Lie group. Is there any meaningful generalisation to (non-manifold) topological groups? Consider for example the Whitehead tower $$ \...
3
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0answers
50 views

What is the topological data for $(\mathbb Z_n)_p$ theories?

Consider the 3d TQFT described by the Lagrangian (Dijkgraaf-Witten with gauge group $\mathbb Z_n$ at level $p$): $$ \mathcal L=\frac{n}{2\pi} B\wedge\mathrm dA+\frac{p}{4\pi}A\wedge\mathrm dA $$ with $...
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0answers
23 views

what is the advantages of using 2-μm operating wavelength light in sdm/mdm technology? [closed]

Most of the work have been done in the communication band but recently there has been emerging interest in extending the operating wavelength of communication system to the short-wave infrared (2 μm). ...
1
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1answer
108 views

what is effective index method which is used to solve modes in rectangular waveguide? [closed]

I actually want to know the basics of effective index methods for solving the optical modes in slab/rectangular waveguides.
2
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0answers
107 views

Are broken time reversal symmetry and inversion symmetry forbidden in a Weyl semimetal?

In much of the literature floating around, it is commonly implied that an important part of obtaining a Weyl semimetal phase is to break either time reversal symmetry or inversion symmetry. However, ...
11
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2answers
336 views

Are there aspects of General Relativity that have yet to be tested?

Good evening everyone, I am new in the field of General Relativity and I have been reading and learning about the subject in recent months. For example, I read several articles about experiments ...
3
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0answers
67 views

What is meant by this variant of the euclidean plane: $\mathbb{R}^2_{\hbar}$?

I am reading some papers in mathematical physics (https://arxiv.org/abs/1006.0977) and I came across the following symbol $\mathbb{R}^2_{\hbar}$ I don't recognize nor could I find any background ...
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0answers
29 views

Reference on discussion about the distinction among Schwarzschild vacua

In Schwarzschild spacetime there are a couple of "vacuum" states: the Boulware vacuum, the Unruh vacuum and the Hartle-Hawking vacuum. I actually don't know if there are others. This is something ...
6
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1answer
252 views

“Weak” and “Strong” topological insulators

For translationally invariant systems, we can define some topological invariant based on the translational symmetry, which is referred to "weak" topological invariant. For example, according to Kitaev'...
3
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1answer
63 views

Does a SUSY Chern-Simons term prevent the dualising of the gauge potential to a scalar?

In 3D $\mathcal{N}=2$ supersymmetric field theory with abelian gauge fields, the gauge field $A_{\mu}$ is often dualised to a real scalar $\gamma$. Does a Chern-Simons term prevent this dual ...
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0answers
53 views

Quadrupole Radiation pattern in GR

What is the equation that can be used to show the quadrupole radiation pattern in general relativity? if one wants to plot the quadruple radiation in GR, what should be done?
2
votes
1answer
131 views

In 3D ${\cal N}=2$ SUSY, the linear multiplet contains a global current. How is this related to the gauge field?

I am reading the paper on 3d $\mathcal{N}=2$ supersymmetry by O. Aharony et al. (https://arxiv.org/abs/hep-th/9703110) and I am a bit confused about linear multiplets in section 2.3. A linear ...
5
votes
1answer
294 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 ...
5
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2answers
204 views

How Quantum Information can be important for fundamental physics?

It seems that Quantum Information has been seriously considered as something very important for fundamental physics, and in particular, to quantum gravity. For example, this is the topic of this ...
1
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1answer
66 views

Is this system somehow one toy model for something more complicated?

Sometimes in Physics one builds a toy model to study some more complicated phenomenon. One example would be the Gross-Neveu model and its relation to QCD. Now, consider the following situation in the ...
3
votes
1answer
85 views

Why is the flux quantized in 4D quantum Hall effect?

I am reading "Topological Field Theory of Time-Reversal Invariant Insulators" by Qi, Hughes, and Zhang (https://arxiv.org/abs/0802.3537). It argues that time reversal invariant (TRI) insulators in 2+1 ...
8
votes
1answer
186 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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0answers
26 views

Obtaining low energy effective model of Bernal stacking bilayer graphene

I am now reading some articles about the electronic properties on Bernal stacking bilayer graphene. (https://arxiv.org/abs/1205.6953). In the section II-C-1, the general procedure of obtaining the ...
4
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1answer
238 views

Relation between cobordism and unitary fusion category classification of TQFT/ SPT phase

In the introduction part of Gaiotto's paper (https://arxiv.org/pdf/1712.07950.pdf), he says "in the context of topological field theory, homotopy-theoretic ideas also lead to the classification of ...
2
votes
1answer
90 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 ...
3
votes
1answer
105 views

Relationship between different $Z_{16}$ classifications

I find that there exist two classifications which have a $Z_{16}$ group structure: The sixteen fold way of classifying Majorana fermions, vortex systems appearing in Kitaev's paper on his honeycomb ...
1
vote
1answer
98 views

What is the actual importance of Dixon's extended bodies theory for fundamental physics?

Disclaimer: I'm unsure if this question fits here. If it doesn't please let me know if it can be modified so that it does. In the end if it simply doesn't fit here, I'll delete it. The motivation for ...
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0answers
32 views

On the optimality of Stabilizer codes

I have been studying about quantum error correction codes, specifically aobut the so-called stabilzer codes, and I wonder if are this class of quantum codes the best codes known (in terms of capacity ...
9
votes
1answer
624 views

On a rigorous definition of Feynman's functional integral$.$

It is often stated that there is no mathematically rigorous definition of Feynman's functional integral, except for some very specific examples. I may be very naïve, but to me there is at least one ...
3
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0answers
91 views

How to get the eigenvalue density contribution $\rho_1(x)$?

I'm studying the $1/N$ expansion beyond the planar limit in matrix models. Currently I'm trying to understand and reproduce the results of: Antisymmetric Wilson loops in $\mathcal N \geq 4$ SYM ...
2
votes
1answer
100 views

Hawking radiation on Kruskal-Szekeres coordinates

Recently a physicist I know said he was interested in the following question: "would one observer following Kruskal-Szekeres coordinates in the presence of a Schwarzschild black hole (i.e., whose ...
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0answers
99 views

Producing double-slit interference in string theory

My full question is What brane configuration most economically reproduces a double-slit interference effect? It was inspired by this question, which asks whether string theory has anything to say ...
4
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0answers
151 views

Different definitions of topological phases

When doing classification of topological phases, one need to formalize the problems mathematically. But, it seems that there are two not obviously equivalent ways to describe topological phases. In ...
4
votes
1answer
861 views

Ground state degeneracy: Spin vs Fermionic language

Let us first consider the Hamiltonian of well-known 1D periodic Ising model as $$ H = -\frac{1}{2} \sum_{j=1}^N \sigma^x_j \sigma^x_{j+1} + \frac{h}{2}\sum_{j=1}^N \sigma^z_j. $$ Now, in the ...
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0answers
86 views

Research about extended bodies in Einstein-Cartan gravity

There is out there an approach to deal with extended bodies in General Relativity due to Dixon that seems to be quite well known and believed to be the correct way to describe such phenomena on this ...
4
votes
1answer
128 views

Wightman's theorem, in terms of time-ordered functions$.$

According to Wightman's theorem, given a set of distributions $\{W_n\}$ satisfying a set of axioms, we may conclude the existence of a set of operators $\{\phi\}$ which satisfy some properties, and ...
3
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0answers
63 views

Books for studying non-linear dynamics [closed]

I've recently developed interest into non-linear dynamics and chaos theory after having read a large part of the book by Steven Strogatz. Is it possible for me to delve into a research area dealing ...
2
votes
1answer
129 views

Quark condensate alignment with Yukawa Higgs couplings

It is well known in QCD that the light quark condensates are a unit matrix in flavor space: $\langle \bar{u}u\rangle=\langle \bar{d}d\rangle=\langle \bar{s}s\rangle\sim\Lambda_{\rm QCD}^3$. Thus, we ...
9
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0answers
429 views

Existence of the Unruh effect

In the paper Quantum field aspect of Unruh problem (and others with similar approaches) the author shows that applying the rigorous algebraic approach to QFT, the derivation of the Unruh effect ...
6
votes
1answer
161 views

Peculiarities of non-Abelian gauge groups: self-coupling and topology

There are two striking aspects of non-Abelian gauge groups (compared to their Abelian cousins): (1) The pure gauge parts of non-Abelian Lagrangians contain self-interaction terms that are trilinear ...
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0answers
436 views

Ising model density of states

1D Ising model: exact result In the 1D Ising model with fixed $J_{ij} = J$, without magnetic field, the density of states (dos) can be calculated exactly. There is a caveat in the case of periodic ...
5
votes
1answer
150 views

SLE applied to theoretical physics (eg. CFT), too untractable? not informative enough?

It is has been 15 years since the SLE area took off, and it helped rigourize known predictions from RG and the conformal invariance of the interface (eg. percolation and Ising) and other applications. ...