64,209 research outputs found
Exact results for five-dimensional superconformal field theories with gravity duals
We apply the technique of supersymmetric localization to exactly compute the
partition function of several large superconformal field theories in
five dimensions that have duals in massive type IIA supergravity. The
localization computations are performed in the non-renormalizable effective
field theories obtained through relevant deformations of the UV superconformal
field theories. We compare the free energy to a holographic computation
of entanglement entropy in the duals and find perfect agreement. In
particular, we reproduce the scaling of the free energy that
was expected from supergravity.Comment: 21 pages, 1 figure; v2 refs added, typos fixe
Counting quantum jumps: a summary and comparison of fixed-time and fluctuating-time statistics in electron transport
In quantum transport through nanoscale devices, fluctuations arise from
various sources: the discreteness of charge carriers, the statistical
non-equilibrium that is required for device operation, and unavoidable quantum
uncertainty. As experimental techniques have improved over the last decade,
measurements of these fluctuations have become available.} They have been
accompanied by a plethora of theoretical literature using many different
fluctuation statistics to describe the quantum transport. In this paper, we
overview three prominent fluctuation statistics: full counting, waiting time,
and first-passage time statistics. We discuss their weaknesses and strengths,
and explain connections between them in terms of renewal theory. In particular,
we discuss how different information can be encoded in different statistics
when the transport is non-renewal, and how this behavior manifests in the
measured physical quantities of open quantum systems. All theoretical results
are illustrated via a demonstrative transport scenario: a Markovian master
equation for a molecular electronic junction with electron-phonon interactions.
{{} We demonstrate that to obtain non-renewal behavior, and thus to have
temporal correlations between successive electron tunneling events, there must
be a strong coupling between tunneling electrons and out-of-equilibrium
quantized molecular vibrations.Comment: 24 pages, 8 figure
Moduli spaces of irregular singular connections
In the geometric version of the Langlands correspondence, irregular singular
point connections play the role of Galois representations with wild
ramification. In this paper, we develop a geometric theory of fundamental
strata to study irregular singular connections on the projective line.
Fundamental strata were originally used to classify cuspidal representations of
the general linear group over a local field. In the geometric setting,
fundamental strata play the role of the leading term of a connection. We
introduce the concept of a regular stratum, which allows us to generalize the
condition that a connection has regular semisimple leading term to connections
with non-integer slope. Finally, we construct a symplectic moduli space of
meromorphic connections on the projective line that contain a regular stratum
at each singular point.Comment: 53 pages. A new section (Section 4.4) has been added making precise
the relationship between formal types and isomorphism classes of formal
connections. Significant revisions and additions have also been made to
Sections 3.1 and 4.3 and the introduction to Section
Exploring Photometric Redshifts as an Optimization Problem: An Ensemble MCMC and Simulated Annealing-Driven Template-Fitting Approach
Using a grid of million elements () adapted from
COSMOS photometric redshift (photo-z) searches, we investigate the general
properties of template-based photo-z likelihood surfaces. We find these
surfaces are filled with numerous local minima and large degeneracies that
generally confound rapid but "greedy" optimization schemes, even with
additional stochastic sampling methods. In order to robustly and efficiently
explore these surfaces, we develop BAD-Z [Brisk Annealing-Driven Redshifts
(Z)], which combines ensemble Markov Chain Monte Carlo (MCMC) sampling with
simulated annealing to sample arbitrarily large, pre-generated grids in
approximately constant time. Using a mock catalog of 384,662 objects, we show
BAD-Z samples times more efficiently compared to a brute-force
counterpart while maintaining similar levels of accuracy. Our results represent
first steps toward designing template-fitting photo-z approaches limited mainly
by memory constraints rather than computation time.Comment: 14 pages, 8 figures; submitted to MNRAS; comments welcom
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