386 research outputs found
GAMMA: A Mathematica package for performing gamma-matrix algebra and Fierz transformations in arbitrary dimensions
We have developed a Mathematica package capable of performing gamma-matrix
algebra in arbitrary (integer) dimensions. As an application we can compute
Fierz transformations.Comment: 12 pages, LaTeX, v2: some clarifications added, updated package
availabl
Non-Commutative Open (p,q)-String Theories
In this paper we make an SL(2,Z)-covariant generalisation of the
noncommutative theories, NCYM and NCOS on the D3-brane, and NCOS on the
D5-brane in type IIB. Usually, the noncommutative theories are obtained by
studying perturbative F-string theory, and the parameters governing the
noncommutative theories are given by the open string data. The S-duality of
NCYM and NCOS on the D3-brane has been seen by dualising the background,
keeping the F-string under study fixed. We give an SL(2,Z)-covariant
generalisation of the open string data relevant when one instead studies
perturbative (p,q)-string theory. The S-duality of NCYM and NCOS on the
D3-brane is reproduced by instead keeping the background fixed and studying
different (p,q)-string theories. We also obtain new noncommutative open
(p,q)-string theories on the D3-brane and the D5-brane which are S-dual to
ordinary NCOS. The theories are studied using the supergravity duals of the
D3-brane and the D5-brane, corresponding to a probe brane in the relevant
background.Comment: AMSLaTeX. 23 pages. Minor clarifications added. To be published in
JHE
Holographic Response of Electron Clouds
In order to make progress towards more realistic models of holographic
fermion physics, we use gauge/gravity duality to compute the dispersion
relations for quasinormal modes and collective modes for the electron cloud
background, i.e. the non-zero temperature version of the electron star. The
results are compared to the corresponding results for the Schwarzschild and
Reissner-Nordstr\"om black hole backgrounds, and the qualitative differences
are highlighted and discussed.Comment: 27 page
On relating multiple M2 and D2-branes
Due to the difficulties of finding superconformal Lagrangian theories for
multiple M2-branes, we will in this paper instead focus on the field equations.
By relaxing the requirement of a Lagrangian formulation we can explore the
possibility of having structure constants satisfying the
fundamental identity but which are not totally antisymmetric. We exemplify this
discussion by making use of an explicit choice of a non-antisymmetric
constructed from the Lie algebra structure constants
of an arbitrary gauge group. Although this choice of does not
admit an obvious Lagrangian description, it does reproduce the correct SYM
theory for a stack of D2-branes to leading order in upon
reduction and, moreover, it sheds new light on the centre of mass coordinates
for multiple M2-branes.Comment: 9 pages, references added and statements concerning the fundamental
identity revise
Off-shell structure of twisted (2,0) theory
A -exact off-shell action is constructed for twisted abelian (2,0) theory
on a Lorentzian six-manifold of the form , where is
a flat two-manifold and is a general Euclidean four-manifold. The
properties of this formulation, which is obtained by introducing two auxiliary
fields, can be summarised by a commutative diagram where the Lagrangian and its
stress-tensor arise from the -variation of two fermionic quantities and
. This completes and extends the analysis in
[arXiv:1311.3300].Comment: 15 pages, 2 figure
Solution of heterotic Killing spinor equations and special geometry
We outline the solution of the Killing spinor equations of the heterotic
supergravity. In addition, we describe the classification of all half
supersymmetric solutions.Comment: 19 page
Anomalously long lifetimes in two-dimensional Fermi liquids
A precise characterization of the recently discovered crossover to
hydrodynamic transport in electron liquids, and in particular of a conjectured
exotic odd-parity transport regime, requires a full solution of the
Fermi-liquid collision integral at all temperatures beyond state-of-the-art
analytic leading-logarithmic approximations. We develop a general basis
expansion of the linearized collision integral applicable at all temperatures,
and employ this to determine the decay rates of Fermi surface perturbations in
two-dimensional electron liquids. In particular, we provide exhaustive data on
the decay rates for a new odd-parity regime, in which parity-even Fermi surface
deformations decay rapidly but odd-parity modes are anomalously long lived. We
find that this transport regime exists at fairly large temperatures , putting this regime within the reach of current experiments.Comment: 6 pages, 3 figure
Holographic Plasmon Relaxation with and without Broken Translations
We study the dynamics and the relaxation of bulk plasmons in strongly coupled
and quantum critical systems using the holographic framework. We analyze the
dispersion relation of the plasmonic modes in detail for an illustrative class
of holographic bottom-up models. Comparing to a simple hydrodynamic formula, we
entangle the complicated interplay between the three least damped modes and
shed light on the underlying physical processes. Such as the dependence of the
plasma frequency and the effective relaxation time in terms of the
electromagnetic coupling, the charge and the temperature of the system.
Introducing momentum dissipation, we then identify its additional contribution
to the damping. Finally, we consider the spontaneous symmetry breaking (SSB) of
translational invariance. Upon dialing the strength of the SSB, we observe an
increase of the longitudinal sound speed controlled by the elastic moduli and a
decrease in the plasma frequency of the gapped plasmon. We comment on the
condensed matter interpretation of this mechanism.Comment: v2: improved discussions, added results in the SSB section,
references added; matching the published version in JHE
Exotic Holographic Dispersion
For strongly interacting systems holographic duality is a powerful framework
for computing e.g. dispersion relations to all orders in perturbation theory.
Using the standard Reissner-Nordst\"om black hole as a holographic model for a
(strange) metal, we obtain exotic dispersion relations for both plasmon modes
and quasinormal modes for certain intermediate values of the charge of the
black hole.
The obtained dispersion relations show dissipative behavior which we compare
to the generic expectations from the Caldeira-Leggett model for quantum
dissipation. Based on these considerations, we investigate how holography can
predict higher order corrections for strongly coupled physics.Comment: 12 pages, 14 figure
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