8,686 research outputs found
Acceleration-Induced Deconfinement Transitions in de Sitter Spacetime
In this note, we consider confining gauge theories in defined by
or compactification of higher-dimensional conformal field theories
with gravity duals. We investigate the behavior of these theories on de Sitter
spacetime as a function of the Hubble parameter. We find that in each case, the
de Sitter vacuum state of the field theory (defined by Euclidian continuation
from a sphere) undergoes a deconfinement transition as the Hubble parameter is
increased past a critical value. In each case, the corresponding critical de
Sitter temperature is smaller than the corresponding Minkowski-space
deconfinement temperature by a factor nearly equal to the dimension of the de
Sitter spacetime. The behavior is qualitatively and quantitatively similar to
that for confining theories defined by compactification of CFTs, studied
recently in arXiv:1007.3996.Comment: 25 pages, 7 figure
Tailoring Three-Point Functions and Integrability III. Classical Tunneling
We compute three-point functions between one large classical operator and two
large BPS operators at weak coupling. We consider operators made out of the
scalars of N=4 SYM, dual to strings moving in the sphere. The three-point
function exponentiates and can be thought of as a classical tunneling process
in which the classical string-like operator decays into two classical BPS
states. From an Integrability/Condensed Matter point of view, we simplified
inner products of spin chain Bethe states in a classical limit corresponding to
long wavelength excitations above the ferromagnetic vacuum. As a by-product we
solved a new long-range Ising model in the thermodynamic limit.Comment: 37 pages, 10 figure
Universal scaling properties of extremal cohesive holographic phases
We show that strongly-coupled, translation-invariant holographic IR phases at
finite density can be classified according to the scaling behaviour of the
metric, the electric potential and the electric flux introducing four critical
exponents, independently of the details of the setup. Solutions fall into two
classes, depending on whether they break relativistic symmetry or not. The
critical exponents determine key properties of these phases, like thermodynamic
stability, the (ir)relevant deformations around them, the low-frequency scaling
of the optical conductivity and the nature of the spectrum for electric
perturbations. We also study the scaling behaviour of the electric flux through
bulk minimal surfaces using the Hartnoll-Radicevic order parameter, and
characterize the deviation from the Ryu-Takayanagi prescription in terms of the
critical exponents.Comment: v4: corrected a typo in eqn (3.29), now (3.28). Conclusions unchange
Entropy from AdS(3)/CFT(2)
We parametrize the (2+1)-dimensional AdS space and the BTZ black hole with
Fefferman-Graham coordinates starting from the AdS boundary. We consider
various boundary metrics: Rindler, static de Sitter and FRW. In each case, we
compute the holographic stress-energy tensor of the dual CFT and confirm that
it has the correct form, including the effects of the conformal anomaly. We
find that the Fefferman-Graham parametrization also spans a second copy of the
AdS space, including a second boundary. For the boundary metrics we consider,
the Fefferman-Graham coordinates do not cover the whole AdS space. We propose
that the length of the line delimiting the excluded region at a given time can
be identified with the entropy of the dual CFT on a background determined by
the boundary metric. For Rindler and de Sitter backgrounds our proposal
reproduces the expected entropy. For a FRW background it produces a
generalization of the Cardy formula that takes into account the vacuum energy
related to the expansion.Comment: major revision with several clarifications and corrections, 22 page
Observation of Kuznetsov-Ma soliton dynamics in optical fibre
The nonlinear Schrödinger equation (NLSE) is a central model of nonlinear science, applying to hydrodynamics, plasma physics, molecular biology and optics. The NLSE admits only few elementary analytic solutions, but one in particular describing a localized soliton on a finite background is of intense current interest in the context of understanding the physics of extreme waves. However, although the first solution of this type was the Kuznetzov-Ma (KM) soliton derived in 1977, there have in fact been no quantitative experiments confirming its validity. We report here novel experiments in optical fibre that confirm the KM soliton theory, completing an important series of experiments that have now observed a complete family of soliton on background solutions to the NLSE. Our results also show that KM dynamics appear more universally than for the specific conditions originally considered, and can be interpreted as an analytic description of Fermi-Pasta-Ulam recurrence in NLSE propagation
Stimulated superconductivity at strong coupling
Stimulating a system with time dependent sources can enhance instabilities,
thus increasing the critical temperature at which the system transitions to
interesting low-temperature phases such as superconductivity or superfluidity.
After reviewing this phenomenon in non-equilibrium BCS theory (and its marginal
fermi liquid generalization) we analyze the effect in holographic
superconductors. We exhibit a simple regime in which the transition temperature
increases parametrically as we increase the frequency of the time-dependent
source.Comment: 19 pages, 2 figure. v3: Comments, references and one figure added.
Version to appear in JHE
Spinning strings and integrable spin chains in the AdS/CFT correspondence
In this introductory review we discuss dynamical tests of the AdS_5 x S^5
string/N=4 super Yang-Mills duality. After a brief introduction to AdS/CFT we
argue that semiclassical string energies yield information on the quantum
spectrum of the string in the limit of large angular momenta on the S^5. The
energies of the folded and circular spinning string solutions rotating on a S^3
within the S^5 are derived, which yield all loop predictions for the dual gauge
theory scaling dimensions. These follow from the eigenvalues of the dilatation
operator of N=4 super Yang-Mills in a minimal SU(2) subsector and we display
its reformulation in terms of a Heisenberg s=1/2 spin chain along with the
coordinate Bethe ansatz for its explicit diagonalization. In order to make
contact to the spinning string energies we then study the thermodynamic limit
of the one-loop gauge theory Bethe equations and demonstrate the matching with
the folded and closed string result at this loop order. Finally the known gauge
theory results at higher-loop orders are reviewed and the associated long-range
spin chain Bethe ansatz is introduced, leading to an asymptotic all-loop
conjecture for the gauge theory Bethe equations. This uncovers discrepancies at
the three-loop order between gauge theory scaling dimensions and string theory
energies and the implications of this are discussed. Along the way we comment
on further developments and generalizations of the subject and point to the
relevant literature.Comment: 40 pages, invited contribution to Living Reviews in Relativity. v2:
improvements in the text and references adde
Scattering of Giant Magnons in CP^3
We study classical scattering phase of CP^2 dyonic giant magnons in R_t x
CP^3. We construct two-soliton solutions explicitly by the dressing method.
Using these solutions, we compute the classical time delays for the scattering
of giant magnons, and compare them to boundstate S-matrix elements derived from
the conjectured AdS_4/CFT_3 S-matrix by Ahn and Nepomechie in the strong
coupling limit. Our result is consistent with the conjectured S-matrix. The
dyonic solutions play an essential role in revealing the polarization
dependence of scattering phase.Comment: 29 pages; v2: minor corrections; v3: minor corrections, references
added ; v4: minor corrections ; v5: minor corrections based on the published
versio
Coherent quantum phase slip
A hundred years after discovery of superconductivity, one fundamental
prediction of the theory, the coherent quantum phase slip (CQPS), has not been
observed. CQPS is a phenomenon exactly dual to the Josephson effect: whilst the
latter is a coherent transfer of charges between superconducting contacts, the
former is a coherent transfer of vortices or fluxes across a superconducting
wire. In contrast to previously reported observations of incoherent phase slip,
the CQPS has been only a subject of theoretical study. Its experimental
demonstration is made difficult by quasiparticle dissipation due to gapless
excitations in nanowires or in vortex cores. This difficulty might be overcome
by using certain strongly disordered superconductors in the vicinity of the
superconductor-insulator transition (SIT). Here we report the first direct
observation of the CQPS in a strongly disordered indium-oxide (InOx)
superconducting wire inserted in a loop, which is manifested by the
superposition of the quantum states with different number of fluxes. Similarly
to the Josephson effect, our observation is expected to lead to novel
applications in superconducting electronics and quantum metrology.Comment: 14 pages, 3 figure
Schr\"odinger Holography with and without Hyperscaling Violation
We study the properties of the Schr\"odinger-type non-relativistic holography
for general dynamical exponent z with and without hyperscaling violation
exponent \theta. The scalar correlation function has a more general form due to
general z as well as the presence of \theta, whose effects also modify the
scaling dimension of the scalar operator. We propose a prescription for minimal
surfaces of this "codimension 2 holography," and demonstrate the (d-1)
dimensional area law for the entanglement entropy from (d+3) dimensional
Schr\"odinger backgrounds. Surprisingly, the area law is violated for d+1 < z <
d+2, even without hyperscaling violation, which interpolates between the
logarithmic violation and extensive volume dependence of entanglement entropy.
Similar violations are also found in the presence of the hyperscaling
violation. Their dual field theories are expected to have novel phases for the
parameter range, including Fermi surface. We also analyze string theory
embeddings using non-relativistic branes.Comment: 62 pages and 6 figures, v2: several typos in section 5 corrected,
references added, v3: typos corrected, references added, published versio
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