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 ...
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1answer
127 views
Unitary transformations in mixed discrete-continuous representations
I am having trouble with the unitary transformation of a certain Hamiltonian in the paper
Zhai, H. Spin-orbit coupled quantum gases. Int. J. Mod. Phys. B 26 no. 1, 1230001 (2012). arXiv:1110.6798 ...
17
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0answers
268 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 have already difficulties in penetrating the literature... I'd highly appreciate any ...
6
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1answer
146 views
Large and small gauge transformations?
I've a questions about the difference between small and large gauge transformations (a small gauge transformation tends to the identity at spatial infinity, whereas the large transformations don't). ...
3
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0answers
42 views
3d Ising Fixed point on general space manifold?
The headline question: Is it known how to construct an equivalent of the 3-D Ising Fixed point theory on an arbitrary 3-D manifold? Or any non-trivial d > 2 fixed point?
The answer is maybe as simple ...
3
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1answer
56 views
Can classical systems exhibit “strong coupling”?
Does the concept of strong coupling mean anything in a classical setting? If strong coupling means just an inability to apply perturbative methods to the Hamiltonian, then obviously yes, we can ...
2
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1answer
49 views
Full calculation of B meson mixing amplitude
I am trying to calculate B mixing in the Standard Model (in preparation to go beyond the SM). I have no trouble doing the gamma matrix algebra etc. but the loop integral keeps tripping me up. In my ...
5
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1answer
90 views
Proof that we can always find a gauge transformation such that $A_0=0$?
I'm trying to follow Coleman's proof from his lectures "Aspects of Symmetry" on page 200-201. He proofs it is always possible to work in the temporal gauge for a general Yang-Mills-Higgs theory. I ...
6
votes
1answer
101 views
Do topological superconductors exhibit symmetry-enriched topological order?
Gapped Hamiltonians with a ground-state having long-range entanglement (LRE), are said to have topological order (TO), while if the ground state is short-range entangled (SRE) they are in the trivial ...
7
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1answer
104 views
About the stability of the ground state of the bosonic string
In Polchinski's string theory vol 1, p. 23, it is said
"It is a complicated question whether the bosonic string has any stable vacuum, and the answer is not known."
The book was published on 1998. ...
7
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1answer
113 views
Experimental signature of topological superconductor
I was wondering if someone can provides some clear experimental signatures of a topological superconductors ?
I was thinking about that, because for topological insulator, one of the hallmarks is ...
6
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1answer
148 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 ...
4
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0answers
76 views
Adiabatic theorem and Berry phase
As far as I can check, the adiabatic theorem in quantum mechanics can be proven exactly when there is no crossing between (pseudo-)time-evolved energy levels. To be a little bit more explicit, one ...
6
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1answer
127 views
What are renormalons from a physics point of view?
This is again a question in the context of this paper about the Exact Renormalization Group. On p 23 and the following few pages, it is explained that for a $\lambda \phi^4$ bare action at the bare ...
5
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1answer
59 views
4D instantons and the moduli space of N=2 on R^3 x S^1
I am reading the paper arXiv:0807.4723 by Gaiotto, Moore, and Neitzke on wall-crossing. I would like to understand whether if the Darboux coordinates in the mutually non-local case contain the ...
5
votes
2answers
178 views
Why is the Fermi surface stable?
As a condensed matter physicist, I take it for granted that a Fermi surface is stable.
But it is stable with respect to what?
For instance, Cooper pairing is known as an instability of the Fermi ...
11
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0answers
200 views
How to evaluate this sum of coupling coefficients?
I would like to evaluate the following summation of Clebsch-Gordan and Wigner 6-j symbols in closed form:
$$\sum_{l,m} C_{l_2,m_2,l_1,m_1}^{l,m} C_{\lambda_2,\mu_2,\lambda_1,\mu_1}^{l,m} \left\{ ...
6
votes
2answers
354 views
What is the most natural new physics one can expect at the TeV scale: new (supersymmetric)particles or some new (non-commutative) spacetime structure?
Up to now, nothing else than one Standard Model (SM) Higgs boson-like resonance has been found at the LHC while many predictions based on effective theories using supersymmetry require several Higgs ...
2
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1answer
71 views
How to justify matter-field interaction for non-gauge-invariant Hamiltonian?
I'm wondering how can one formally justify the electromagnetic response of a system which does not verify local U(1) gauge invariance.
A good example of what I would like to consider is given by the ...
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2answers
38 views
About the microscopic form of magnetocrystalline anisotropy
Currently people write magnetocrystalline anisotropy as
$H_{an}=-K s_x^2$
from its classical counterpart:
$H_{an}=-K ( \sin \theta)^2$
where $K$ is the anisotropy constant, but for spin 1/2, $s_x^2$ ...
3
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0answers
141 views
What are endomorphism bundle valued $p$-forms and exterior covariant derivatives and their use in Chern-Simons theory?
Chern-Simons Forms appears in several places in physics for examples,
Fractional Quantum Hall Effect,
response of Topological Insulator,
invariant of knot,
electromagnetism in 2+1 space-time, ...
5
votes
1answer
88 views
Background Gauge Condition In Moduli Space
I'm really confused on the background gauge condition for the moduli space of BPS-monopoles:
\begin{equation}
D_i \delta A_i + e [\phi , \delta \phi]=0
\end{equation}
I can see that this conditions ...
2
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0answers
96 views
Holographic Field Theory
I am trying to read this paper http://arxiv.org/abs/1204.1780 and I don't understand how to get from eqn 91 which is,
$$S_{2} = N^{2} \{V[P^{(1)}_{m}] + (J^{(1)m} - \mathcal{J}^{m})P_{m}^{(1)}\} ...
6
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0answers
58 views
Is it possible to derive the brane action in pure supergravity?
The branes that source the RR fields of supergravity are described by the DBI action plus a CS term. I know this only from superstring considerations.
Is there a way to find this result without ...
3
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0answers
241 views
Toward the establishment of non-equilibrium (quasi-equilibrium) magnon BEC theory
In 2006, Demokritov et al have reported that they have achieved the observation of quasi-equilibrium magnon Bose-Einstein condensation (BEC) in YIG at finite (room) temperature by using the method ...
3
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0answers
51 views
How do Aharony et. al conclude that all scalar fields in the supergravity multiplet are periodic?
This question is for anyone who has read/gone through the paper above or knows anything about AdS/CFT. The paper can be found here.
On page 46, eq. (2.33), the author finds solutions to the scalar ...
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0answers
27 views
Can TOTEM's T2 detector measure differential cross sections?
My current research involves making a prediction for data collected by the TOTEM experiment at the LHC. The experiment is primarily designed to measure the total inelastic and elastic scattering cross ...
5
votes
1answer
76 views
Conserved currents in higher-spin theories
After the proposal of Maldacena (AdS/CFT), there have been numerous attempts to find out gravity duals of various kinds of CFT. Klebanov and Polyakov gave one such correspondence here. The claim is ...
9
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1answer
247 views
Is there a “covariant derivative” for conformal transformation?
A primary field is defined by its behavior under a conformal transformation $x\rightarrow x'(x)$:
$$\phi(x)\rightarrow\phi'(x')=\left|\frac{\partial x'}{\partial x}\right|^{-h}\phi(x)$$
It's fairly ...
4
votes
2answers
146 views
What is the importance of the Fermi energy $E_F$ or the chem. potential $\mu$ for topological superconductors
A lot of effort is put into shifting the Fermi energy of a topological insulator to exactly zero which then provides some advantages when this TI is coupled with a superconductor.
I don't understand ...
4
votes
2answers
151 views
Whis is the difference between charge fractionalization in 1D and 2D?
Both 1D Polyacetelene and 2D fractional quantum Hall state can support fractional excitations.
But as I can see, there are some differences: the ground state of Polyacetelene breaks translational ...
3
votes
1answer
158 views
How to define the mirror symmetry operator for Kane-Mele model?
Let us take the famous Kane-Mele(KM) model(http://prl.aps.org/abstract/PRL/v95/i22/e226801 and http://prl.aps.org/abstract/PRL/v95/i14/e146802) as our starting point.
Due to the time-reversal(TR), ...
1
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1answer
34 views
Name of a state with $d-1$ excitations, distributed uniformly among $n$ qudits
Is there a particular name for a quantum state of the form (up to the normalization):
$$\sum_{i_1+\ldots+i_n = d-1} |i_1\rangle |i_2\rangle \ldots |i_n\rangle$$
or was it studied is some papers?
...
2
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0answers
134 views
Field content and symmetry groups of Minimal Composite Higgs Models
I'm trying to teach myself the Composite Higgs Model, both its theory and its LHC phenomenology (particularly the 4DCHM). Unfortunately, I'm struggling; the literature is contradictory and/or omits ...
13
votes
2answers
414 views
What does the sum of two qubits tell about their correlations?
How much can I learn about correlations between two quits by measuring
the sum of their values? What is the best way to formalize such a
question?
Below is my original, longer formulation of ...
2
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0answers
57 views
Robot controling pouring process from a bottle
I need to solve a problem within mechanic of fluids for a part of my thesis. Robot will pick up a bottle of beer, cola, julebrus or any other kind of beverage. And then it has to bring it to the glass ...
3
votes
2answers
161 views
Second baryon octet
Let's temporarily ignore spin. If 3 denotes the standard representation of SU(3), 1 the trivial rep, 8 the adjoint rep and 10 the symmetric cube then it's well-known that
3 x 3 x 3 = 1 + 8 + 8 + 10
...
7
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2answers
3k views
Some Korean researchers saying that they solved Yang-mill existence and mass gap problem
Today, Korean media is reporting that a team of South Korean researchers solved Yang-Mill existence and mass gap problem. Did anyone outside Korea even notice this? I was not able to notice anything ...
4
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0answers
110 views
Looking for modern results in semiclassical physics and relevant references
What are some important approximations, especially those that are state-of-the-art, used to approximate the many-body dynamics of atoms and molecules in the semiclassical regime? To be clear, I'm not ...
3
votes
1answer
95 views
Transformation law for fermionic measure in functional integral
I am reading the paper "Bosonization in a Two-Dimensional Riemann-Cartan Geometry", Il Nuovo Cimento B Series 11
11 Marzo 1987, Volume 98, Issue 1, pp 25-36, ...
5
votes
1answer
198 views
A question on the doped Kitaev-Heisenberg model?
Recently, some groups have studied the effects of doping the Kitaev model on honeycomb lattice(e.g.,http://arxiv.org/abs/1109.6681 and http://arxiv.org/abs/1109.4155) and their calculations show the ...
10
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1answer
270 views
What is the “BCS Cooper pair condensation” as a physical phenomenon in terms of experiments?
"Thought" experiments and "numerical" experiments are allowed.
This question is motivated by the question Has BCS Cooper pair condensate been observed in experiment? ,
and by our recent research on ...
2
votes
2answers
124 views
How is the energy/eigenvalue gap plot drawn for adiabatic quantum computation?
I was going through arXiv:quant-ph/0001106v1, the first paper by Farhi on adiabatic quantum computation.
Equation 2.24 says, $$\tilde{H}(s) = (1-s)H_B + sH_P$$ which means the adiabatic evolution ...
1
vote
2answers
231 views
How much pure math should a physics/microelectronics person know [duplicate]
I do condensed matter physics modeling in my phd and I was struck up learning quite an amount of physics. But while having done lot of physics courses, I see that if I learn pure math I would ...
4
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0answers
85 views
Electric potential of a spheroidal gaussian
I'm looking for results that compute the electrostatic potential due to a spheroidal gaussian distribution. Specifically, I'm looking for solutions of equations of the form
$$
...
7
votes
0answers
161 views
Local explanation of the Aharonov-Bohm effect in terms of force fields
Here is an interesting paper for the Physics SE community: On the role of potentials in the Aharonov-Bohm effect, Lev Vaidman, published in PHYSICAL REVIEW A 86, 040101(R) (2012).
You should check it ...
19
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0answers
398 views
Sigma Models on Riemann Surfaces
I'm interested in knowing whether sigma models with an $n$-sheeted Riemann surface as the target space have been considered in the literature. To be explicit, these would have the action ...
5
votes
0answers
112 views
Has hep-th/0312070 forgotten to fix $s_{0} = 1/2$ for the fermionic states in the second table on page 52?
Link to the original paper: The Gauge/String Correspondence Towards Realistic Gauge Theories (arXiv paper)
On page 52 we see that, for a theory of Dp-branes placed at an orbifold (orbifold = ...
14
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2answers
633 views
Topological Charge. What is it Physically?
I have seen the term topological charge defined in an abstract mathematical way as a essentially a labeling scheme for particles which follows certain rules. However I am left guessing when trying to ...
7
votes
1answer
219 views
Canonical quantization in supersymmetric quantum mechanics
Suppose you have a theory of maps
$\phi: {\cal T} \to M$
with $M$ some Riemannian manifold,
Lagrangian
$$L~=~ \frac12 g_{ij}\dot\phi^i\dot\phi^j + \frac{i}{2}g_{ij}(\overline{\psi}^i ...
4
votes
1answer
145 views
Notation in Spin Liquid
When construct spin liquid by projective symmetry group, we can classified spin liquids by the invariant group (IGG) of their mean field ansatze. For example, we can have Z2, U(1) and SU(2) spin ...
