140 research outputs found
Entanglement Entropy in Lifshitz Theories
We discuss and compute entanglement entropy (EE) in (1+1)-dimensional free
Lifshitz scalar field theories with arbitrary dynamical exponents. We consider
both the subinterval and periodic sublattices in the discretized theory as
subsystems. In both cases, we are able to analytically demonstrate that the EE
grows linearly as a function of the dynamical exponent. Furthermore, for the
subinterval case, we determine that as the dynamical exponent increases, there
is a crossover from an area law to a volume law. Lastly, we deform Lifshitz
field theories with certain relevant operators and show that the EE decreases
from the ultraviolet to the infrared fixed point, giving evidence for a
possible c-theorem for deformed Lifshitz theories.Comment: 24 pages, 8 figures; v2: Clarified discussions in Subsection 3.3 and
appendix; v3: Major extension of results, including an analytic computation
of subinterval entanglement in massless scalar Lifshitz theories; v4: Added
footnote 4 for clarification, version to appear in SciPos
Instanton Solutions for the Universal Hypermultiplet
We expand our previous analysis on fivebrane and membrane instanton solutions
in the universal hypermultiplet, including near-extremal multi-centered
solutions and mixed fivebrane-membrane charged instantons. The results are most
conveniently described in terms of a double-tensor multiplet.Comment: Minor changes, clarification added. Contribution to the proceedings
of the 36th International Symposium Ahrenshoop, August 200
Order parameter fluctuations in the holographic superconductor
We investigate the effect of order parameter fluctuations in the holographic
superconductor. In particular, using a fully backreacted bulk geometry, the
intrinsic spectral functions of the order parameter in both the normal and the
superconducting phase are computed. We also present a vector-like large-
version of the Ginzburg-Landau model that accurately describes our
long-wavelength results in both phases. The large- limit of the latter model
explains why the Higgs mode and the second-sound mode are not present in the
spectral functions. Our results indicate that the holographic superconductor
describes a relativistic multi-component superfluid in the universal regime of
the BEC-BCS crossover.Comment: 21 pages, 15 figures; version accepted for publicatio
Self-dual Einstein Spaces, Heavenly Metrics and Twistors
Four-dimensional quaternion-Kahler metrics, or equivalently self-dual
Einstein spaces M, are known to be encoded locally into one real function h
subject to Przanowski's Heavenly equation. We elucidate the relation between
this description and the usual twistor description for quaternion-Kahler
spaces. In particular, we show that the same space M can be described by
infinitely many different solutions h, associated to different complex (local)
submanifolds on the twistor space, and therefore to different (local)
integrable complex structures on M. We also study quaternion-Kahler
deformations of M and, in the special case where M has a Killing vector field,
show that the corresponding variations of h are related to eigenmodes of the
conformal Laplacian on M. We exemplify our findings on the four-sphere S^4, the
hyperbolic plane H^4 and on the "universal hypermultiplet", i.e. the
hypermultiplet moduli space in type IIA string compactified on a rigid
Calabi-Yau threefold.Comment: 44 pages, 1 figure; misprints correcte
D-instantons and twistors: some exact results
We present some results on instanton corrections to the hypermultiplet moduli
space in Calabi-Yau compactifications of Type II string theories. Previously,
using twistor methods, only a class of D-instantons (D2-instantons wrapping
A-cycles) was incorporated exactly and the rest was treated only linearly. We
go beyond the linear approximation and give a set of holomorphic functions
which, through a known procedure, capture the effect of D-instantons at all
orders. Moreover, we show that for a sector where all instanton charges have
vanishing symplectic invariant scalar product, the hypermultiplet metric can be
computed explicitly.Comment: 32 pages, 3 figures, uses JHEP3.cls; some changes in section 3.3.3;
corrected formula for the contact potentia
Multi-Instanton Calculus and the AdS/CFT Correspondence in N=4 Superconformal Field Theory
We present a self-contained study of ADHM multi-instantons in SU(N) gauge theory, especially the novel interplay with supersymmetry and the large-N limit. We give both field- and string-theoretic derivations of the N=4 supersymmetric multi-instanton action and collective coordinate integration measure. As a central application, we focus on certain n-point functions G_n, n=16, 8 or 4, in N=4 SU(N) gauge theory at the conformal point (as well as on related higher-partial-wave correlators); these are correlators in which the 16 exact supersymmetric and superconformal fermion zero modes are saturated. In the large-N limit, for the first time in any 4-dimensional theory, we are able to evaluate all leading-order multi-instanton contributions exactly. We find compelling evidence for Maldacena's conjecture: (1) The large-N k-instanton collective coordinate space has the geometry of a single copy of AdS_5 x S^5. (2) The integration measure on this space includes the partition function of 10-dimensional N=1 SU(k) gauge theory dimensionally reduced to 0 dimensions, matching the description of D-instantons in Type IIB string theory. (3) In exact agreement with Type IIB string calculations, at the k-instanton level, G_n = \sqrt{N} g^8 k^{n-7/2} e^{2\pi ik\tau} \sum_{d|k} d^{-2} F_n(x_1,...,x_n), where F_n is identical to a convolution of n bulk-to-boundary supergravity propagators
Instantons in the Double-Tensor Multiplet
The double-tensor multiplet naturally appears in type IIB superstring
compactifications on Calabi-Yau threefolds, and is dual to the universal
hypermultiplet. We revisit the calculation of instanton corrections to the
low-energy effective action, in the supergravity approximation. We derive a
Bogomolny'i bound for the double-tensor multiplet and find new instanton
solutions saturating the bound. They are characterized by the topological
charges and the asymptotic values of the scalar fields in the double-tensor
multiplet.Comment: 17 pages, LaTeX2e with amsmath.sty; v2: minor change
Hypermultiplets and Topological Strings
The c-map relates classical hypermultiplet moduli spaces in compactifications
of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces
via a further compactification on a circle. We give an off-shell description of
the c-map in N=2 superspace. The superspace Lagrangian for the hypermultiplets
is a single function directly related to the prepotential of special geometry,
and can therefore be computed using topological string theory. Similarly, a
class of higher derivative terms for hypermultiplets can be computed from the
higher genus topological string amplitudes. Our results provide a framework for
studying quantum corrections to the hypermultiplet moduli space, as well as for
understanding the black hole wave-function as a function of the hypermultiplet
moduli.Comment: 21 pages, references adde
Theory of Ultracold Superstrings
The combination of a vortex line in a one-dimensional optical lattice with
fermions bound to the vortex core makes up an ultracold superstring. We give a
detailed derivation of the way to make this supersymmetric string in the
laboratory. In particular, we discuss the presence of a fermionic bound state
in the vortex core and the tuning of the laser beams needed to achieve
supersymmetry. Moreover, we discuss experimental consequences of supersymmetry
and identify the precise supersymmetry in the problem. Finally, we make the
mathematical connection with string theory.Comment: 16 pages, 9 figures, important factor 2 corrected, accepted for
publication in PR
N=2 supergravity in five dimensions revisited
We construct matter-coupled N=2 supergravity in five dimensions, using the
superconformal approach. For the matter sector we take an arbitrary number of
vector-, tensor- and hyper-multiplets. By allowing off-diagonal vector-tensor
couplings we find more general results than currently known in the literature.
Our results provide the appropriate starting point for a systematic search for
BPS solutions, and for applications of M-theory compactifications on Calabi-Yau
manifolds with fluxes.Comment: 35 pages; v.2: A sign changed in a bilinear fermion term in (5.7
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