25 research outputs found
S-duality invariant perturbation theory improved by holography
We study anomalous dimensions of unprotected low twist operators in the
four-dimensional supersymmetric Yang-Mills theory. We
construct a class of interpolating functions to approximate the dimensions of
the leading twist operators for arbitrary gauge coupling . The
interpolating functions are consistent with previous results on the
perturbation theory, holographic computation and full S-duality. We use our
interpolating functions to test a recent conjecture by the
superconformal bootstrap that upper bounds on the dimensions are saturated at
one of the duality-invariant points and . It turns
out that our interpolating functions have maximum at , which
are close to the conjectural values by the conformal bootstrap. In terms of the
interpolating functions, we draw the image of conformal manifold in the space
of the dimensions. We find that the image is almost a line despite the
conformal manifold is two-dimensional. We also construct interpolating
functions for the subleading twist operator and study level crossing phenomenon
between the leading and subleading twist operators. Finally we study the
dimension of the Konishi operator in the planar limit. We find that our
interpolating functions match with numerical result obtained by Thermodynamic
Bethe Ansatz very well. It turns out that analytic properties of the
interpolating functions reflect an expectation on a radius of convergence of
the perturbation theory.Comment: 39+14 pages, 22 figures; v3: minor correction
Heat Kernels on the AdS(2) cone and Logarithmic Corrections to Extremal Black Hole Entropy
We develop new techniques to efficiently evaluate heat kernel coefficients
for the Laplacian in the short-time expansion on spheres and hyperboloids with
conical singularities. We then apply these techniques to explicitly compute the
logarithmic contribution to black hole entropy from an N=4 vector multiplet
about a Z(N) orbifold of the near-horizon geometry of quarter--BPS black holes
in N=4 supergravity. We find that this vanishes, matching perfectly with the
prediction from the microstate counting. We also discuss possible
generalisations of our heat kernel results to higher-spin fields over Z(N)
orbifolds of higher-dimensional spheres and hyperboloids.Comment: 41 page
Second order transport from anomalies
We study parity odd transport at second order in derivative expansion for a
non-conformal charged fluid. We see that there are 27 parity odd transport
coefficients, of which 12 are non-vanishing in equilibrium. We use the
equilibrium partition function method to express 7 of these in terms of the
anomaly, shear viscosity, charge diffusivity and thermodynamic functions. The
remaining 5 are constrained by 3 relations which also involve the anomaly. We
derive Kubo formulae for 2 of the transport coefficients and show these agree
with that derived from the equilibrium partition function.Comment: Error in total number of independent parity odd transport
coefficients has been corrected from 29 to 27. Results for the relation of
the transport coefficients to the anomaly unchanged. Added a section on
chiral dispersion relations, includes additional references. Added two
appendices and corrected some typos. 34 page
Higher Spin Cosmology
We construct cosmological solutions of higher spin gravity in 2+1 dimensional
de Sitter space. We show that a consistent thermodynamics can be obtained for
their horizons by demanding appropriate holonomy conditions. This is equivalent
to demanding the integrability of the Euclidean boundary CFT partition
function, and reduces to Gibbons-Hawking thermodynamics in the spin-2 case. By
using a prescription of Maldacena, we relate the thermodynamics of these
solutions to those of higher spin black holes in AdS_3.Comment: 21 pages, v2: many typos fixed, refs added, v3: minor
corrections/improvements, Phys. Rev. D version, v4: one more re
Inevitable manifestation of wiggles in the expansion of the late Universe
Using the fact that the comoving angular diameter distance to the last
scattering surface is strictly constrained almost model independently, we show
that, for any model agreeing with the standard CDM model on its
background dynamics at and size of the comoving sound horizon at last
scattering, the deviations of the Hubble radius from the one of the standard
CDM model must be a member of the set of admissible wavelets. The
family of models characterized by this framework also offers nontrivial
oscillatory behaviours in various functions that define the kinematics of the
Universe, even when the wavelets themselves are very simple. We also discuss
the consequences of attributing these kinematics to, first, dark energy, and
second, varying gravitational coupling strength. Utilizing some simplest
wavelets, we demonstrate the competence of this framework in describing the
baryon acoustic oscillation (BAO) data without any modifications to the
agreement with cosmic microwave background measurements. This framework also
provides a natural explanation for the bumps found in nonparametric
observational reconstructions of the Hubble parameter and dark energy density
as compensations of the dips suggested by some BAO data, and questions the
physical reality of their existence. We note that utilizing this framework on
top of the models that agree with both the cosmic microwave background and
local measurements but are held back by BAO data, one may resurrect these
models through the wiggly nature of wavelets that can naturally accommodate the
BAO data. Finally, we also suggest narrowing the plausible set of admissible
wavelets to further improve our framework by imposing conditions from expected
kinematics of a viable cosmological model or first principle fundamental
physics such as energy conditions.Comment: 16 pages, 4 figures; matches the version published in Physical Review
On the dynamical generation and decay of cosmological anisotropies
We present a simple model which dynamically generates cosmological
anisotropies on top of standard FLRW geometry. This is in some sense
reminiscent of the mean field approximation, where the mean field cosmological
model under consideration would be the standard FLRW, and the dynamical
anisotropy is a small perturbative correction on top of it. Using a
supergravity-inspired model, we confirm that the stable fixed point of our
model corresponds to standard FLRW cosmology. We use a Bianchi VII-type
model supplemented with an axion-like particle (ALP) and gauge fields,
and we show that the anisotropies of the geometry are dynamically generated by
the non-trivial interaction between the gravity sector and the gauge
sector. Studying the attractor flow, we show that the anisotropies are present
at early times (high redshift) and decay asymptotically to an FLRW attractor
fixed point. With such a mechanism, observations of non-isotropy are not
contradictory to FLRW geometry or indeed the CDM model. Such models
could in principle shed some insights on the present cosmological tensions.Comment: 15 pages, 9 figure