57 research outputs found
Evolution of edge states in topological superfluids during the quantum phase transition
The quantum phase transition between topological and non-topological
insulators or between fully gapped superfluids/superconductors can occur
without closing the gap. We consider the evolution of the Majorana edge states
on the surface of topological superconductor during transition to the
topologically trivial superconductor on example of non-interacting Hamiltonian
describing the spin-triplet superfluid 3He-B. In conventional situation when
the gap is nullified at the transition, the spectrum of Majorana fermions
shrinks and vanishes after the transition to the trivial state. If the
topological transition occurs without the gap closing, the Majorana fermion
spectrum disappears by escaping to ultraviolet, where Green's function
approaches zero. This demonstrates the close connection between the topological
transition without closing the gap and zeroes in the Green's function. Similar
connection takes place in interacting systems where zeroes may occur due to
interaction.Comment: 5 pages, 2 figures, JETP Letters style, version submitted to JETP
Letter
Instabilities of Black Strings and Branes
We review recent progress on the instabilities of black strings and branes
both for pure Einstein gravity as well as supergravity theories which are
relevant for string theory. We focus mainly on Gregory-Laflamme instabilities.
In the first part of the review we provide a detailed discussion of the
classical gravitational instability of the neutral uniform black string in
higher dimensional gravity. The uniform black string is part of a larger phase
diagram of Kaluza-Klein black holes which will be discussed thoroughly. This
phase diagram exhibits many interesting features including new phases,
non-uniqueness and horizon-topology changing transitions. In the second part,
we turn to charged black branes in supergravity and show how the
Gregory-Laflamme instability of the neutral black string implies via a
boost/U-duality map similar instabilities for non- and near-extremal smeared
branes in string theory. We also comment on instabilities of D-brane bound
states. The connection between classical and thermodynamic stability, known as
the correlated stability conjecture, is also reviewed and illustrated with
examples. Finally, we examine the holographic implications of the
Gregory-Laflamme instability for a number of non-gravitational theories
including Yang-Mills theories and Little String Theory.Comment: 119 pages, 16 figures. Invited review for Classical and Quantum
Gravit
Geons with spin and charge
We construct new geon-type black holes in D>3 dimensions for Einstein's
theory coupled to gauge fields. A static nondegenerate vacuum black hole has a
geon quotient provided the spatial section admits a suitable discrete isometry,
and an antisymmetric tensor field of rank 2 or D-2 with a pure F^2 action can
be included by an appropriate (and in most cases nontrivial) choice of the
field strength bundle. We find rotating geons as quotients of the
Myers-Perry(-AdS) solution when D is odd and not equal to 7. For other D we
show that such rotating geons, if they exist at all, cannot be continuously
deformed to zero angular momentum. With a negative cosmological constant, we
construct geons with angular momenta on a torus at the infinity. As an example
of a nonabelian gauge field, we show that the D=4 spherically symmetric SU(2)
black hole admits a geon version with a trivial gauge bundle. Various
generalisations, including both black-brane geons and Yang-Mills theories with
Chern-Simons terms, are briefly discussed.Comment: 26 pages, 1 figure. LaTeX with amssymb, amsmath. (v2: References and
a figure added.
Big Bang Models in String Theory
These proceedings are based on lectures delivered at the "RTN Winter School
on Strings, Supergravity and Gauge Theories", CERN, January 16 - January 20,
2006. The school was mainly aimed at Ph.D. students and young postdocs. The
lectures start with a brief introduction to spacetime singularities and the
string theory resolution of certain static singularities. Then they discuss
attempts to resolve cosmological singularities in string theory, mainly
focusing on two specific examples: the Milne orbifold and the matrix big bang.Comment: 44 pages, 18 figures; v2: misprints in section 4.2 fixed (corrects
published version), reference adde
Specific heat of 2D interacting Majorana fermions from holography
Majorana fermions are a fascinating medium for discovering new phases of matter. However, the standard analytical tools are very limited in probing the non-perturbative aspects of interacting Majoranas in more than one dimensions. Here, we employ the holographic correspondence to determine the specific heat of a two-dimensional interacting gapless Majorana system. To perform our analysis we first describe the interactions in terms of a pseudo-scalar torsion field. We then allow fluctuations in the background curvature thus identifying our model with a (2â+â1)-dimensional Anti-de Sitter (AdS) geometry with torsion. By employing the AdS/CFT correspondence, we show that the interacting model is dual to a (1â+â1)-dimensional conformal field theory (CFT) with central charge that depends on the interaction coupling. This non-perturbative result enables us to determine the effect interactions have in the specific heat of the system at the zero temperature limit
Multiobjective Optimization for Synthesizing Compressor-Aided Distillation Sequences with Heat Integration
A Novel Method for Assessing the Effect of Pressure on VaporâLiquid Equilibrium in Ternary Systems
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