# Tagged Questions

The study of physical properties condensed phases of matter, including solids and liquids.

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### Proper definition of the Wannier function

I am studying the construction of the Wannier functions for 1D system with periodic boundary conditions and my reasoning seems to be a little bit different from what I can find in textbooks. First ...
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### Sublattice symmetry vs Particle hole symmetry

Sublattice symmetry and particle hole symmetry generally constrain a system's energy spectrum to be symmetric with respect to fermi level. My understanding is that they are both represented by an ...
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### Majorana fermion [on hold]

I know that in condensed matter physics Majorana fermion is neutral and one fermion can be split into two Majorana fermions and vise versa. My question is charge. Two neutral particles can merge into ...
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### Switching Parity in a Superconductor

I've got a pretty simple question that's been bothering me for a while. This is the issue. Suppose we have a superconductor with phase $\phi$, and we change this to $\phi+2\pi$. One would think that ...
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### Why are topological phases described by modular tensor categories?

After some reading, I have an inuitive idea what topological phases of matter are. But where is the connection to modular tensor categories? Is there fundamental literature where this is covered?
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### Renormalization Group in Condensed Matter [on hold]

Are RG calculations done only in the vicinity of a phase transitions in cond-matt?
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### How does superfluids and Bose-Einstein Condensates form?

Superfluids or Bose-Einstein Condensates can form from bosonic particles (such as the integer spin 0 $^4\mathrm{He}$) at low temperatures near absolute zero when all the bosonic particles in it start ...
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### Can superfluids pass through ordinary baryonic matter?

Since superfluids consists of integer spin bosons or effective bosonic Cooper-paired fermions, Pauli Exclusion Principle does not apply to them. They can thus occupy the same quantum state as any ...
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### Systems with extensive ground state degeneracy

This is sort of a follow up to this question: What does it mean for a Hamiltonian or system to be gapped or gapless? There it is stated in one of the answers that a system is gapped if it fulfills ...
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### What is the recursive relation for three-particle Green's functions?

In condensed matter physics, one often choose to study the many-body Green's functions (GF) with the diagram (perturbation) expansion technique. In what follows only two-body interaction is concerned. ...
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### Ionic polarisation: wave-vector of photon ~ 0

While discussing ionic polarization due to electromagnetic waves we discuss interaction of photons and ions of crystal. Now, the next step is to take conservation of momentum under consideration. ...
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### Examples of short-range correlated gapless systems

I thought this must have been asked before, but couldn't find it through search. It was proved by Hastings and Koma in arXiv:math-ph/0507008, given a Hamiltonian satisfying certain locality ...
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### Does Bose-Einstein Condensate other than liquid helium exist?

I have basic understanding of BEC - if you can call it understanding -, and I did a lot of reading to get it, but I never came across any examples other than liquid helium. Is it theoretically ...
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### Projected band structure plot - orbital characteristics plotted vs the K values?

I'm not understanding what is it that I have to plot for obtaining the orbital characteristics of a band in the band structure diagram. Usually we plot the energy eigenvalues for a given k point. ...
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### Decomposition of the Time-Evolution Operator: Translationally Invariant MPO

Hello everyone myself Sudipto. Currently I'm learning the matrix product state technique in order to simulate 1d spin system and study different properties of the system form quantum information ...
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### Why alloy have more resistance?

Is there any simple way to understand why alloy have more resistance than metals? My teacher ask this, I answer that, there might be more free electrons in metals than an alloy, but she said you are ...
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### Vacuum persistance amplitude

E. Fradkin's Field Theories in Condensed Matter Physics formulas 3.57 and 3.58: I feel really sad about it, but all my tries of getting from formula  Z = \operatorname{tr} \hat{T} \prod_{j=1}^{...
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### Is there a block spin renormalization group scheme that preserves Kramers-Wannier duality?

Block spin renormalization group (RG) (or real space RG) is an approach to studying statistical mechanics models of spins on the lattice. In particular, I am interested in the 2D square lattice model ...
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### How do signals go through solid objects? [closed]

So many types of signals pass, or seem to pass I don't know, through solid objects. How do they do this?
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### RPA Charge Instability in One Dimensional Electronic Systems

As we know, no long range order in a one dimensional electron system is expected due to quantum fluctuation. A typical 'phase diagram' for a system with short-range interactions is shown on page 69 of ...