721 research outputs found
Multilevel Diversity Coding with Secure Regeneration: Separate Coding Achieves the MBR Point
The problem of multilevel diversity coding with secure regeneration (MDC-SR)
is considered, which includes the problems of multilevel diversity coding with
regeneration (MDC-R) and secure regenerating code (SRC) as special cases. Two
outer bounds are established, showing that separate coding of different
messages using the respective SRCs can achieve the
minimum-bandwidth-regeneration (MBR) point of the achievable normalized
storage-capacity repair-bandwidth tradeoff regions for the general MDC-SR
problem. The core of the new converse results is an exchange lemma, which can
be established using Han's subset inequality
Composite Quantum Phases in Non-Hermitian Systems
Non-Hermitian systems have attracted considerable interest in recent years
owing to their unique topological properties that are absent in Hermitian
systems. While such properties have been thoroughly characterized in free
fermion models, they remain an open question for interacting bosonic systems.
In this Letter, we present a precise definition of quantum phases for
non-Hermitian systems and propose a new family of phases referred to as
composite quantum phases. We demonstrate the existence of these phases in a
one-dimensional spin- system and show their robustness against perturbations
through numerical simulations. Furthermore, we investigate the phase diagram of
our model, indicating the extensive presence of these new phases in
non-Hermitian systems. Our work establishes a new framework for studying and
constructing quantum phases in non-Hermitian interacting systems, revealing
exciting possibilities beyond the single-particle picture.Comment: 9 pages, 5 figure
Deforming black holes with even multipolar differential rotation boundary
Motivated by the novel asymptotically global AdS solutions with deforming
horizon in [JHEP {\bf 1802}, 060 (2018)], we analyze the boundary metric with
even multipolar differential rotation and numerically construct a family of
deforming solutions with quadrupolar differential rotation boundary, including
two classes of solutions: solitons and black holes. In contrast to solutions
with dipolar differential rotation boundary, we find that even though the norm
of Killing vector becomes spacelike for certain regions of polar
angle when , solitons and black holes with quadrupolar
differential rotation still exist and do not develop hair due to superradiance.
Moreover, at the same temperature, the horizonal deformation of quadrupolar
rotation is smaller than that of dipolar rotation. Furthermore, we also study
the entropy and quasinormal modes of the solutions, which have the analogous
properties to that of dipolar rotation.Comment: 18 pages, 21 figure
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