Recent content by Physics Monkey

Hey nonequilibrium, This is the XY model. It is exactly solvable using free fermions and there is no symmetry breaking in the model. The fermion ground state is a Fermi gas which is translation invariant, time reversal invariant, and preserves spin rotation symmetry. Note that, if I...

Regarding 1, I would argue that any theory which is not anomalous can be put on a lattice. In practice the lattice model may need to be heavily fine tuned to reach to the target theory in the IR. I'm curious in what context you've heard it claimed that N=2 SUSY YM cannot be put on a lattice?

As far as I understand the proposal, what one requires is that the system approaches a UV fixed point at high energies. The fixed point could be non-interacting but generically I would expect some order one dimensionless interaction strength. Although I haven't thought carefully about it, I...

http://www.latimes.com/science/sciencenow/la-sci-sn-stephen-hawking-black-hole-information-paradox-20150826-story.html in the LA Times is enlightening. There are a few salient quotes from Strominger at the end of the article.

It is definitely closely related but I think Penna does have a new twist in that he considers hair at the horizon in addition to null infinty. SZ seem only to talk about hair at null infinity. EDIT: It's not really clear to me how these two sets of symmetries are related.

I would like to discuss a bit this paper (http://arxiv.org/abs/1508.06577): BMS invariance and the membrane paradigm Robert F. Penna (Submitted on 26 Aug 2015) We reinterpret the BMS invariance of gravitational scattering using the membrane paradigm. BMS symmetries imply an infinite number of...

It looks to me like http://arxiv.org/abs/1508.06577 by R. Penna, which just appeared last night, is a very closely related proposal. BMS invariance and the membrane paradigm Robert F. Penna (Submitted on 26 Aug 2015) We reinterpret the BMS invariance of gravitational scattering using the...

I think the effects of acceleration on entanglement depend on the physical manifestation of the logical state. For example, http://arxiv.org/abs/1006.1394v3 considers entangled states made of modes of scalar and spinor fields. Since these modes transform non-trivially under accelerations it is...

Classically the wormhole grows forever, but if the wormhole growth is dual to the growth of complexity in the quantum state then because complexity cannot be too large the classical picture of eternal wormhole growth must also break down. If the entropy of the black hole is S and we model the...

Hi all, I'm interested in the behavior of electric fields in a gravitational shockwave geometry. I'm specifically thinking about gravitational shockwaves due to null shells as discussed, for example, in Dray-'tHooft http://www.sciencedirect.com/science/article/pii/0550321385905255 (available...

On the question of information loss I can say one thing. I believe that any finite bond dimension MERA (meaning all the lines in the tensor network are finite dimensional) will not be able to exactly capture a conformal field theory (CFT) ground state. This is true even if the CFT is regulated...

I don't seem to have the book and can't find the relevant part to preview online. I did find some other uses of normal ordering in the book which seem consistent with my usual understanding and the definition you gave. I am also not aware of any special normal ordering prescription in condensed...

Usually it just means deleting the degrees of freedom outside some region and removing all the terms in the Hamiltonian that coupled to them. However, sometimes one adds additional boundary-only terms as part of the general notion of open boundary conditions. In the context of DMRG to the best...

The basic statements that flesh out the analogy are as follows. Classical: Requiring probabilities to add to one requires that the integral of the phase space distribution over all phase space must be one. Liouville's theorem implies that this integral is independent of time. So if the...

The most direct way I know to obtain this answer is just to carefully write out all the projection operators on a case by case basis. For example, if x=y=0 so that (x AND y) = 0 then the win conditions are a=b=0 or a=b=1 so that (a XOR b) = 0. Since x=y=0 Alice and Bob are measuring Z and (Z+X)...