21 research outputs found
Quantum Current Algebra for the Superstring
The sigma model describing the dynamics of the superstring in the background can be constructed using the coset
. A basic set of operators in this two
dimensional conformal field theory is composed by the left invariant currents.
Since these currents are not (anti) holomorphic, their OPE's is not determined
by symmetry principles and its computation should be performed perturbatively.
Using the pure spinor sigma model for this background, we compute the one-loop
correction to these OPE's. We also compute the OPE's of the left invariant
currents with the energy momentum tensor at tree level and one loop.Comment: 28 pages, 12 figures, v2: typos corrected
First-principles derivation of the AdS/CFT Y-systems
We provide a first-principles, perturbative derivation of the AdS5/CFT4
Y-system that has been proposed to solve the spectrum problem of N=4 SYM. The
proof relies on the computation of quantum effects in the fusion of some loop
operators, namely the transfer matrices. More precisely we show that the
leading quantum corrections in the fusion of transfer matrices induce the
correct shifts of the spectral parameter in the T-system. As intermediate steps
we study UV divergences in line operators up to first order and compute the
fusion of line operators up to second order for the pure spinor string in
AdS5xS5. We also argue that the derivation can be easily extended to other
integrable models, some of which describe string theory on AdS4, AdS3 and AdS2
spacetimes.Comment: 45 pages, 5 figures; v2: minor additions, JHEP versio
Bosonic Fractionalisation Transitions
At finite density, charge in holographic systems can be sourced either by
explicit matter sources in the bulk or by bulk horizons. In this paper we find
bosonic solutions of both types, breaking a global U(1) symmetry in the former
case and leaving it unbroken in the latter. Using a minimal bottom-up model we
exhibit phase transitions between the two cases, under the influence of a
relevant operator in the dual field theory. We also embed solutions and
transitions of this type in M-theory, where, holding the theory at constant
chemical potential, the cohesive phase is connected to a neutral phase of
Schr\"odinger type via a z=2 QCP.Comment: references added. minor changes. version published in JHE
Holographic three-point functions of semiclassical states
We calculate the holographic three-point functions in N = 4 super-Yang-Mills
theory in the case when two of the operators are semiclassical and one is dual
to a supergravity mode. We further discuss the transition to the regime when
all three operators are semiclassical.Comment: 17 pages, 3 figures; v2: refs. added, discussion in sec. 2.1
expanded; v3: misprint in (2.28) corrected, published versio
Stellar spectroscopy: Fermions and holographic Lifshitz criticality
Electron stars are fluids of charged fermions in Anti-de Sitter spacetime.
They are candidate holographic duals for gauge theories at finite charge
density and exhibit emergent Lifshitz scaling at low energies. This paper
computes in detail the field theory Green's function G^R(w,k) of the
gauge-invariant fermionic operators making up the star. The Green's function
contains a large number of closely spaced Fermi surfaces, the volumes of which
add up to the total charge density in accordance with the Luttinger count.
Excitations of the Fermi surfaces are long lived for w <~ k^z. Beyond w ~ k^z
the fermionic quasiparticles dissipate strongly into the critical Lifshitz
sector. Fermions near this critical dispersion relation give interesting
contributions to the optical conductivity.Comment: 38 pages + appendices. 9 figure
Friedel Oscillations in Holographic Metals
In this article we study the conditions under which holographic metallic
states display Friedel oscillations. We focus on systems where the bulk charge
density is not hidden behind a black hole horizon. Understanding holographic
Friedel oscillations gives a clean way to characterize the boundary system,
complementary to probe fermion calculations. We find that fermions in a "hard
wall" AdS geometry unambiguously display Friedel oscillations. However, similar
oscillations are washed out for electron stars, suggesting a smeared continuum
of Fermi surfaces.Comment: 26 pages, 5 figure
Strings on Semisymmetric Superspaces
Several string backgrounds which arise in the AdS/CFT correspondence are
described by integrable sigma-models. Their target space is always a Z(4)
supercoset (a semi-symmetric superspace). Here we list all semi-symmetric
cosets which have zero beta function and central charge c<=26 at one loop in
perturbation theory.Comment: 25 pages, 1 figur
Stringy Stability of Charged Dilaton Black Holes with Flat Event Horizon
Electrically charged black holes with flat event horizon in anti-de Sitter
space have received much attention due to various applications in Anti-de
Sitter/Conformal Field Theory (AdS/CFT) correspondence, from modeling the
behavior of quark-gluon plasma to superconductor. Crucial to the physics on the
dual field theory is the fact that when embedded in string theory, black holes
in the bulk may become vulnerable to instability caused by brane
pair-production. Since dilaton arises naturally in the context of string
theory, we study the effect of coupling dilaton to Maxwell field on the
stability of flat charged AdS black holes. In particular, we study the
stability of Gao-Zhang black holes, which are locally asymptotically anti-de
Sitter. We find that for dilaton coupling parameter > 1, flat black
holes are stable against brane pair production, however for 0 < < 1,
the black holes eventually become unstable as the amount of electrical charges
is increased. Such instability however, behaves somewhat differently from that
of flat Reissner-Nordstr\"om black holes. In addition, we prove that the
Seiberg-Witten action of charged dilaton AdS black hole of Gao-Zhang type with
flat event horizon (at least in 5-dimension) is always logarithmically
divergent at infinity for finite values of , and is finite and positive
in the case tends to infinity . We also comment on the robustness of
our result for other charged dilaton black holes that are not of Gao-Zhang
type.Comment: Fixed some confusions regarding whether part of the discussions
concern electrically charged hole or magnetically charged one. No changes to
the result