1,286 research outputs found
Supersymmetric hydrodynamics from the AdS/CFT correspondence
We compute holographically the dispersion relation for a hydrodynamic mode of
fluctuation (the phonino) of the density of supersymmetry current in N = 4 SYM
at strong coupling. The mode appears as a pole at low frequency and momentum in
the correlator of supercurrents. It has a wave-like propagation, and we find
its speed and coefficient of attenuation.Comment: 17 page
Flavor corrections to the entanglement entropy
We consider the holographic entanglement entropy in N=4 SYM coupled to
massive flavor degrees of freedom. The flavors are introduced by putting D7
branes in AdS_5. The resulting geometry including the backreaction of the
branes is known in a perturbation expansion in the ratio N_f/N_c. We consider
the expansion to first order, and compute the entanglement entropy of a region
of the boundary. We consider two different cases for the geometry of the
region: a slab and a ball. We find analytic solutions for the minimal surfaces
in the bulk whose area gives the entropy, and analyze the structure of the UV
divergence and the dependence on the masses. Our results confirm the general
structure that was predicted by free field theory calculations, but with
coefficients that depend on the coupling.Comment: 17 pages, 1 figure, references adde
Super-Chern-Simons Theory as Superstring Theory
Superstrings and topological strings with supermanifolds as target space play
a central role in the recent developments in string theory. Nevertheless the
rules for higher-genus computations are still unclear or guessed in analogy
with bosonic and fermionic strings. Here we present a common geometrical
setting to develop systematically the prescription for amplitude computations.
The geometrical origin of these difficulties is the theory of integration of
superforms. We provide a translation between the theory of supermanifolds and
topological strings with supertarget space. We show how in this formulation one
can naturally construct picture changing operators to be inserted in the
correlation functions to soak up the zero modes of commuting ghost and we
derive the amplitude prescriptions from the coupling with an extended
topological gravity on the worldsheet. As an application we consider a simple
model on R^(3|2) leading to super-Chern-Simons theory.Comment: hravmac, 50p
Circuit Complexity and 2D Bosonisation
We consider the circuit complexity of free bosons, or equivalently free
fermions, in 1+1 dimensions. Motivated by the results of [1] and [2, 3] who
found different behavior in the complexity of free bosons and fermions, in any
dimension, we consider the 1+1 dimensional case where, thanks to the
bosonisation equivalence, we can consider the same state from both the bosonic
and the fermionic perspectives. In this way the discrepancy can be attributed
to a different choice of the set of gates allowed in the circuit. We study the
effect in two classes of states: i) bosonic-coherent / fermionic-gaussian
states; ii) states that are both bosonic- and fermionic-gaussian. We consider
the complexity relative to the ground state. In the first class, the different
results can be reconciled admitting a mode-dependent cost function in one of
the descriptions. The differences in the second class are more important, in
terms of the cutoff-dependence and the overall behavior of the complexity.Comment: Fix typos and add reference
Phenomenological characterisation of semi-holographic non-Fermi liquids
We analyse some phenomenological implications of the most general
semi-holographic models for non-Fermi liquids that have emerged with inputs
from the holographic correspondence. We find generalizations of Landau-Silin
equations with few parameters governing thermodynamics, low energy response and
collective excitations. We show that even when there is a Fermi surface with
well-defined quasi-particle excitations, the collective excitations can behave
very differently from Landau's theory.Comment: 5+5 pages, 3 figures, expanded supplementary material, published
versio
Diffusion constant of supercharge density in N=4 SYM at finite chemical potential
We compute holographically the diffusion constant of supercharges in N=4 SYM
at finite chemical potential for the R-charge, by solving the equations of
motion for the transverse mode of the gravitino in the STU black hole in 5
dimensions. We consider the case of one charge and three charges, and we
present analytical solutions for small values of the charges and numerical
solutions for arbitrary values. We compare our results with other known results
in 4 dimensions.Comment: 20 pages, 4 figures; v2: typos correcte
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