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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11
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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 $^...
5
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1answer
402 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 ...
1
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0answers
52 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 ...
2
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0answers
88 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 ...
5
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0answers
71 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
68 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 $...
1
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0answers
27 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). ...
2
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1answer
2k 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.
3
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0answers
242 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
votes
2answers
395 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
71 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 ...
6
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1answer
773 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
76 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 ...
2
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1answer
252 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 ...
6
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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 ...
6
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2answers
258 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
vote
1answer
77 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
151 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
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 $N$ ...
6
votes
1answer
354 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
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 ...
6
votes
1answer
202 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
192 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 ...
2
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0answers
36 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 ...
10
votes
1answer
832 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
votes
0answers
94 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
185 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 ...
1
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0answers
178 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 ...
5
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0answers
243 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 ...
5
votes
1answer
2k 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 ...
4
votes
1answer
218 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
78 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
158 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 ...
16
votes
1answer
660 views

Existence of the Unruh effect

In the paper Quantum field aspect of Unruh problem (and others with similar approaches) Buchholz and Verch show that applying the rigorous algebraic approach to QFT, the derivation of the Unruh effect ...
6
votes
1answer
192 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 ...
3
votes
0answers
812 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 ...
4
votes
1answer
182 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. ...
2
votes
0answers
49 views

Superconductor-insulator transition at finite temperatures

I know that it is possible to have a phase transition at $T=0$ between a superconductor and an insulator. The mechanism is not the "usual" QPT as the system is not translationally invariant: the ...
2
votes
0answers
72 views

Algebraic curves from (quiver) gauge theory

I'm interested in algebraic curves one can associate to gauge or string theories. Examples involve Seiberg-Witten curves or family of A-polynomials which define holomorphic Lagrangian submanifolds for ...
2
votes
0answers
82 views

Energy of states in non-equilibrium systems

In equilibrium thermodynamics, the Boltzmann distribution gives the probability of finding a system in a certain $i$: $P_i = e^{-\frac{E_i}{k_B T}}$. Conversely, by measuring state probabilities one ...
5
votes
1answer
510 views

Perturbative Results Kitaev Model with Magnetic Field

I am curious if there are results available for the Kitaev model with a magnetic field -- in his 2006 paper, Kitaev obtains the form of the effective hamiltonian (Eq. 46 in https://arxiv.org/abs/cond-...
-2
votes
1answer
126 views

Discovery of anti-deuteron and the implication of CPT violation

From this review by Antonino Zichichi 2009 and this review from T. D. Lee in 2007, it is said that Dirac is very upset when hearing the discovery of anti-deuteron (anti-matter of deuteron, the nucleus ...
0
votes
1answer
72 views

How likely is it that 'Einstein spontaneous transition rate" in these papers refers to the rate of spontaneous emission?

In a prior question I sorta posed the question "What is the Einstein spontaneous transition rate for the selected line?" The main question wasn't really focused on it, and (as of writing this) the ...
1
vote
1answer
370 views

Wigner function for a Lorentzian function

I am calculating the Wigner function for a Lorentzian function, which is the Fourier transform of the exp(-|x|) damping function. But I am having a problem normalizing this function, as I am getting ...
0
votes
0answers
52 views

Where does this equation for ionic abundances come from, and what does it mean?

So I've been attempting to find ionic abundances using visual emission spectra of planetary nebula, and I ran across an equation to do that in the paper Abundances of planetary nebulae NGC 40 and NGC ...
1
vote
0answers
108 views

Calculate comoving distance as a function of density parameters

I'm constructing a likelihood function which has parameters the density parameters found in the Friedman equation found using massive gravity action $H$: $$H(z)^2=a + b (1 + z) + c (1 + z)^2 + d (1 + ...
3
votes
0answers
420 views

The replica trick for interacting fields

The replica trick is essentially a mathematical trick of the form: $$\ln Z = \lim\limits_{n\rightarrow 0}\frac{\partial}{\partial n}\ln Z^n$$ Intuitively, we think of making $n$ copies of a system (in ...
4
votes
0answers
231 views

Plasma physics with application to nuclear fusion research internship [closed]

I am looking for research opportunities for undergraduates in the field of plasma physics. I have found a couple program like SULI but need several more. I would like to know about more programs out ...
0
votes
1answer
43 views

Postlinear gravitational wave generation by Thorne et. al

My question is related to this paper. In this paper, Thorne and Kovacs considered the so-called postlinear gravitational wave formalism. Basically, you want to take into account the influence of the ...
5
votes
1answer
141 views

Scalar field transformation behaviour of N=4 SYM after a topological twist

Why do scalars transform as 2-forms after a topological twist? I'm currently looking at this paper https://arxiv.org/abs/1403.2530. There they analyze a topological twist on N=4 SYM theory on Kähler ...

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