223 research outputs found
Inflation and Holography in String Theory
The encoding of an inflating patch of space-time in terms of a dual theory is
discussed. Following Bousso's interpretation of the holographic principle, we
find that those are generically described not by states in the dual theory but
by density matrices. We try to implement this idea on simple deformations of
the AdS/CFT examples, and an argument is given as to why inflation is so
elusive to string theory.Comment: 15 pages, LaTeX, 2 figures. Uses psbox.te
On the Matter of the Dijkgraaf--Vafa Conjecture
With the aim of extending the gauge theory -- matrix model connection to more
general matter representations, we prove that for various two-index tensors of
the classical gauge groups, the perturbative contributions to the glueball
superpotential reduce to matrix integrals. Contributing diagrams consist of
certain combinations of spheres, disks, and projective planes, which we
evaluate to four and five loop order. In the case of with antisymmetric
matter, independent results are obtained by computing the nonperturbative
superpotential for and 8. Comparison with the Dijkgraaf-Vafa approach
reveals agreement up to loops in matrix model perturbation theory, with
disagreement setting in at loops, being the dual Coxeter number.
At this order, the glueball superfield begins to obey nontrivial relations
due to its underlying structure as a product of fermionic superfields. We
therefore find a relatively simple example of an gauge theory
admitting a large expansion, whose dynamically generated superpotential
differs from the one obtained in the matrix model approach.Comment: 20 pages, harvmac. v2: added comments and reference
dS/CFT correspondence on a brane
We study branes moving in an AdS Schwarzschild black hole background. When
the brane tension exceeds a critical value, the induced metric on the brane is
of FRW type and asymptotically de Sitter. We discuss the relevance of such
configurations to dS/CFT correspondence. When the black hole mass reaches a
critical value that depends on the brane tension, the brane interpolates in the
infinite past and future between a dS space and a finite space of zero Hubble
constant. This corresponds to a cosmological evolution without a Big Bang or a
Big Crunch. Moreover, the central charge of the CFT dual to the dS brane enters
the Cardy-Verlinde formula that gives the entropy of the thermal CFT dual to
the bulk AdS black hole.Comment: 15 pages, 1 figure, v2 references adde
Quantum Criticality via Magnetic Branes
Holographic methods are used to investigate the low temperature limit,
including quantum critical behavior, of strongly coupled 4-dimensional gauge
theories in the presence of an external magnetic field, and finite charge
density. In addition to the metric, the dual gravity theory contains a Maxwell
field with Chern-Simons coupling. In the absence of charge, the magnetic field
induces an RG flow to an infrared AdS geometry, which is
dual to a 2-dimensional CFT representing strongly interacting fermions in the
lowest Landau level. Two asymptotic Virasoro algebras and one chiral Kac-Moody
algebra arise as {\sl emergent symmetries} in the IR. Including a nonzero
charge density reveals a quantum critical point when the magnetic field reaches
a critical value whose scale is set by the charge density. The critical theory
is probed by the study of long-distance correlation functions of the boundary
stress tensor and current. All quantities of major physical interest in this
system, such as critical exponents and scaling functions, can be computed
analytically. We also study an asymptotically AdS system whose magnetic
field induced quantum critical point is governed by a IR Lifshitz geometry,
holographically dual to a D=2+1 field theory. The behavior of these holographic
theories shares important similarities with that of real world quantum critical
systems obtained by tuning a magnetic field, and may be relevant to materials
such as Strontium Ruthenates.Comment: To appear in Lect. Notes Phys. "Strongly interacting matter in
magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Ye
On the energy-momentum tensor for a scalar field on manifolds with boundaries
We argue that already at classical level the energy-momentum tensor for a
scalar field on manifolds with boundaries in addition to the bulk part contains
a contribution located on the boundary. Using the standard variational
procedure for the action with the boundary term, the expression for the surface
energy-momentum tensor is derived for arbitrary bulk and boundary geometries.
Integral conservation laws are investigated. The corresponding conserved
charges are constructed and their relation to the proper densities is
discussed. Further we study the vacuum expectation value of the energy-momentum
tensor in the corresponding quantum field theory. It is shown that the surface
term in the energy-momentum tensor is essential to obtain the equality between
the vacuum energy, evaluated as the sum of the zero-point energies for each
normal mode of frequency, and the energy derived by the integration of the
corresponding vacuum energy density. As an application, by using the zeta
function technique, we evaluate the surface energy for a quantum scalar field
confined inside a spherical shell.Comment: 25 pages, 2 figures, section and appendix on the surface energy for a
spherical shell are added, references added, accepted for publication in
Phys. Rev.
The effect of higher derivative correction on and conductivities in STU model
In this paper we study the ratio of shear viscosity to entropy, electrical
and thermal conductivities for the R-charged black hole in STU model. We
generalize previous works to the case of a black hole with three different
charges. Actually we use diffusion constant to obtain ratio of shear viscosity
to entropy. By applying the thermodynamical stability we recover previous
results. Also we investigate the effect of higher derivative corrections.Comment: revised versio
Obstructions to the Existence of Sasaki-Einstein Metrics
We describe two simple obstructions to the existence of Ricci-flat Kahler
cone metrics on isolated Gorenstein singularities or, equivalently, to the
existence of Sasaki-Einstein metrics on the links of these singularities. In
particular, this also leads to new obstructions for Kahler-Einstein metrics on
Fano orbifolds. We present several families of hypersurface singularities that
are obstructed, including 3-fold and 4-fold singularities of ADE type that have
been studied previously in the physics literature. We show that the AdS/CFT
dual of one obstruction is that the R-charge of a gauge invariant chiral
primary operator violates the unitarity bound.Comment: 35 pages, 1 figure; references and a footnote adde
Phases of N=1 Supersymmetric SO/Sp Gauge Theories via Matrix Model
We extend the results of Cachazo, Seiberg and Witten to N=1 supersymmetric
gauge theories with gauge groups SO(2N), SO(2N+1) and Sp(2N). By taking the
superpotential which is an arbitrary polynomial of adjoint matter \Phi as a
small perturbation of N=2 gauge theories, we examine the singular points
preserving N=1 supersymmetry in the moduli space where mutually local monopoles
become massless. We derive the matrix model complex curve for the whole range
of the degree of perturbed superpotential. Then we determine a generalized
Konishi anomaly equation implying the orientifold contribution. We turn to the
multiplication map and the confinement index K and describe both Coulomb branch
and confining branch. In particular, we construct a multiplication map from
SO(2N+1) to SO(2KN-K+2) where K is an even integer as well as a multiplication
map from SO(2N) to SO(2KN-2K+2) (K is a positive integer), a map from SO(2N+1)
to SO(2KN-K+2) (K is an odd integer) and a map from Sp(2N) to Sp(2KN+2K-2).
Finally we analyze some examples which show some duality: the same moduli space
has two different semiclassical limits corresponding to distinct gauge groups.Comment: 55pp; two paragraphs in page 19 added to clarify the relation between
confinement index and multiplication map index, refs added and to appear in
JHEP; Konishi anomaly equations corrected and some comments on the
degenerated cases for SO(7) and SO(8) adde
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
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