1,002 research outputs found
Anomaly-corrected supersymmetry algebra and supersymmetric holographic renormalization
We present a systematic approach to supersymmetric holographic
renormalization for a generic 5D gauged supergravity theory
with matter multiplets, including its fermionic sector, with all gauge fields
consistently set to zero. We determine the complete set of supersymmetric local
boundary counterterms, including the finite counterterms that parameterize the
choice of supersymmetric renormalization scheme. This allows us to derive
holographically the superconformal Ward identities of a 4D superconformal field
theory on a generic background, including the Weyl and super-Weyl anomalies.
Moreover, we show that these anomalies satisfy the Wess-Zumino consistency
condition. The super-Weyl anomaly implies that the fermionic operators of the
dual field theory, such as the supercurrent, do not transform as tensors under
rigid supersymmetry on backgrounds that admit a conformal Killing spinor, and
their anticommutator with the conserved supercharge contains anomalous terms.
This property is explicitly checked for a toy model. Finally, using the
anomalous transformation of the supercurrent, we obtain the anomaly-corrected
supersymmetry algebra on curved backgrounds admitting a conformal Killing
spinor.Comment: 51 pages; v2: two references added, typos corrected, a discussion
about the 2-dimensional super-Weyl anomaly added in section
Various Aspects of Holographic Renormalization
In this thesis we explore various aspects of holographic renormalization. The thesis comprises the work done by the candidate during the doctorate programme at SISSA and ICTP under the supervision of A. Tanzini. This consists in the following works.
\begin{itemize}
\item In \cite{An:2016fzu}, reproduced in chapter \ref{asy-conical} we consider holographic renormalization in an exotic spacetime such as an asymptotically conical manifold, showing that it has a close relation with variational principle. The variational problem of gravity theories is directly related to black hole thermodynamics. For asymptotically locally AdS backgrounds it is known that holographic renormalization results in a variational principle in terms of equivalence classes of boundary data under the local asymptotic symmetries of the theory, which automatically leads to finite conserved charges satisfying the first law of thermodynamics. We show that this connection holds well beyond asymptotically AdS black holes. In particular, we formulate the variational problem for STU supergravity in four dimensions with boundary conditions corresponding to those obeyed by the so-called `subtracted geometries'. We show that such boundary conditions can be imposed covariantly in terms of a set of asymptotic second class constraints, and we derive the appropriate boundary terms that render the variational problem well posed in two different duality frames of the STU model. This allows us to define finite conserved charges associated with any asymptotic Killing vector and to demonstrate that these charges satisfy the Smarr formula and the first law of thermodynamics. Moreover, by uplifting the theory to five dimensions and then reducing on a 2-sphere, we provide a precise map between the thermodynamic observables of the subtracted geometries and those of the BTZ black hole. Surface terms play a crucial role in this identification.
\item In \cite{An:2017ihs}, reproduced in chapter \ref{susy-holo} we present a systematic approach to supersymmetric holographic renormalization for a generic 5D gauged supergravity theory with matter multiplets, including its fermionic sector, with all gauge fields consistently set to zero. We determine the complete set of supersymmetric local boundary counterterms, including the finite counterterms that parameterize the choice of supersymmetric renormalization scheme. This allows us to derive holographically the superconformal Ward identities of a 4D superconformal field theory on a generic background, including the Weyl and super-Weyl anomalies. Moreover, we show that these anomalies satisfy the Wess-Zumino consistency condition. The super-Weyl anomaly implies that the fermionic operators of the dual field theory, such as the supercurrent, do not transform as tensors under rigid supersymmetry on backgrounds that admit a conformal Killing spinor, and their anticommutator with the conserved supercharge contains anomalous terms. This property is explicitly checked for a toy model. Finally, using the anomalous transformation of the supercurrent, we obtain the anomaly-corrected supersymmetry algebra on curved backgrounds admitting a conformal Killing spinor.
\end{itemize
Black hole thermodynamics from a variational principle: asymptotically conical backgrounds
The variational problem of gravity theories is directly related to black hole thermodynamics. For asymptotically locally AdS backgrounds it is known that holographic renormalization results in a variational principle in terms of equivalence classes of boundary data under the local asymptotic symmetries of the theory, which automatically leads to finite conserved charges satisfying the first law of thermodynamics. We show that this connection holds well beyond asymptotically AdS black holes. In particular, we formulate the variational problem for STU supergravity in four dimensions with boundary conditions corresponding to those obeyed by the so called `subtracted geometries'. We show that such boundary conditions can be imposed covariantly in terms of a set of asymptotic second class constraints, and we derive the appropriate boundary terms that render the variational problem well posed in two different duality frames of the STU model. This allows us to define finite conserved charges associated with any asymptotic Killing vector and to demonstrate that these charges satisfy the Smarr formula and the first law of thermodynamics. Moreover, by uplifting the theory to five dimensions and then reducing on a 2-sphere, we provide a precise map between the thermodynamic observables of the subtracted geometries and those of the BTZ black hole. Surface terms play a crucial role in this identification
Notes on the post-bounce background dynamics in bouncing cosmologies
We investigate the post-bounce background dynamics in a certain class of
single bounce scenarios studied in the literature, in which the cosmic bounce
is driven by a scalar field with negative exponential potential such as the
ekpyrotic potential. We show that those models can actually lead to cyclic
evolutions with repeated bounces. These cyclic evolutions, however, do not
account for the currently observed late-time accelerated expansion and hence
are not cosmologically viable. In this respect we consider a new kind of cyclic
model proposed recently and derive some cosmological constraints on this model.Comment: 26 pages, 15 figures. Significantly revised and accepted version for
JHE
Iatrogenic Left Internal Mammary Artery to Great Cardiac Vein Anastomosis Treated With Coil Embolization
Inadvertent left internal mammary artery (LIMA)-great cardiac vein (GCV) anastomosis is a rare complication of coronary artery bypass graft surgery. Patients with iatrogenic aortocoronary fistula (ACF) were usually treated surgical repair, percutaneous embolic occlusion with coil or balloon. We report a case of iatrogenic LIMA to GCV anastomosis successfully treated with coil embolization and protected left main coronary intervention through the percutaneous transfemoral approach
Random walk with barriers: Diffusion restricted by permeable membranes
Restrictions to molecular motion by barriers (membranes) are ubiquitous in
biological tissues, porous media and composite materials. A major challenge is
to characterize the microstructure of a material or an organism
nondestructively using a bulk transport measurement. Here we demonstrate how
the long-range structural correlations introduced by permeable membranes give
rise to distinct features of transport. We consider Brownian motion restricted
by randomly placed and oriented permeable membranes and focus on the
disorder-averaged diffusion propagator using a scattering approach. The
renormalization group solution reveals a scaling behavior of the diffusion
coefficient for large times, with a characteristically slow inverse square root
time dependence. The predicted time dependence of the diffusion coefficient
agrees well with Monte Carlo simulations in two dimensions. Our results can be
used to identify permeable membranes as restrictions to transport in disordered
materials and in biological tissues, and to quantify their permeability and
surface area.Comment: 8 pages, 3 figures; origin of dispersion clarified, refs adde
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