22 research outputs found
Geodesic congruences in acoustic spacetimes and the role of Raychaudhuri equation
It has been known that the propagation of sound in fluids can be used to
model acoustic spacetimes. These acoustic spacetimes offer analogue models for
gravity. We use the Raychaudhuri equation to study the propagation of sound in
these fluids, which, via the Eikonal approximation, correspond to null geodesic
congruences in the acoustic spacetimes. We explore this within the acoustic
analogues of black holes and cosmological spacetimes. The robustness of the
Raychaudhuri equation and the limits of the acoustic analogue are emphasised
Superconducting Quantum Circuits in the light of Dirac's Constraint Analysis Framework
In this work we introduce a new framework - Dirac's Hamiltonian formalism of
constraint systems - to study different types of Superconducting Quantum
Circuits (SQC) in a {\it{unified}} and unambiguous way. The Lagrangian of a SQC
reveals the constraints, that are classified in a Hamiltonian framework, such
that redundant variables can be removed to isolate the canonical degrees of
freedom for subsequent quantization of the Dirac Brackets via a generalized
Correspondence Principle. This purely algebraic approach makes the application
of concepts such as graph theory, null vector, loop charge,\ etc that are in
vogue, (each for a specific type of circuit), completely redundant
Random geometry at an infinite-randomness fixed point
We study the low-energy physics of the critical (2+1)-dimensional random
transverse-field Ising model. The one-dimensional version of the model is a
paradigmatic example of a system governed by an infinite-randomness fixed
point, for which many results on the distributions of observables are known via
an asymptotically exact renormalization group (RG) approach. In two dimensions,
the same RG rules have been implemented numerically, and demonstrate a flow to
infinite randomness. However, analytical understanding of the structure of this
RG has remained elusive due to the development of geometrical structure in the
graph of interacting spins. To understand the character of the fixed point, we
consider the RG flow acting on a joint ensemble of graphs and couplings. We
propose that the RG effectively occurs in two stages: (1) randomization of the
interaction graph until it belongs to a certain ensemble of random
triangulations of the plane, and (2) a flow of the distributions of couplings
to infinite randomness while the graph ensemble remains invariant. This picture
is substantiated by a numerical RG in which one obtains a steady-state graph
degree distribution and subsequently infinite-randomness scaling distributions
of the couplings. Both of these aspects of the RG flow can be approximately
reproduced in simplified analytical models.Comment: 28 pages, 13 figure
Analytical theory of pyrochlore cooperative paramagnets
The pyrochlore lattice is associated with several potential and actual spin
liquid phases as a result of its strong geometric frustration. At finite
temperature, these can exhibit an unusually broad cross-over regime to a
conventional paramagnet. Here, we study this regime analytically by showing how
a single-tetrahedron Hamiltonian can extrapolate beyond the first term of a
high-temperature expansion and yield insights into the build-up of
correlations. We discuss how this unusual behaviour is brought about by the
structure of the eigenspaces of the coupling matrix. Further interesting
behaviour can appear for parameter values located near phase transitions: we
find coexistence of rods and peaks in the structure factor, as
observed in neutron scattering experiments on YbTiO.Comment: 7 pages, 4 figure
Emergent symmetry near a CDW multicritical point
We consider the critical behavior associated with incommensurate
unidirectional charge-density-wave ordering in a weakly orthorhombic system
subject to uniaxial strain as an experimentally significant example of
multicriticality. We show that, depending on microscopic
details, the phase diagram can have qualitatively different structures which
can involve a vestigial meta-nematic critical point, a pair of tricritical
points, a decoupled tetracritical point, or (at least at mean-field level) a
bicritical point. We analyze the emergent symmetries in the critical regime and
find that these can -- at least in some cases -- involve an emergent
order parameter symmetry.Comment: 7 pages, 2 figure
SpeechNet: Weakly Supervised, End-to-End Speech Recognition at Industrial Scale
End-to-end automatic speech recognition systems represent the state of the
art, but they rely on thousands of hours of manually annotated speech for
training, as well as heavyweight computation for inference. Of course, this
impedes commercialization since most companies lack vast human and
computational resources. In this paper, we explore training and deploying an
ASR system in the label-scarce, compute-limited setting. To reduce human labor,
we use a third-party ASR system as a weak supervision source, supplemented with
labeling functions derived from implicit user feedback. To accelerate
inference, we propose to route production-time queries across a pool of CUDA
graphs of varying input lengths, the distribution of which best matches the
traffic's. Compared to our third-party ASR, we achieve a relative improvement
in word-error rate of 8% and a speedup of 600%. Our system, called SpeechNet,
currently serves 12 million queries per day on our voice-enabled smart
television. To our knowledge, this is the first time a large-scale,
Wav2vec-based deployment has been described in the academic literature.Comment: Accepted to EMNLP 2022 Industry Track; 9 pages, 7 figure
Repurposing Anti-Inflammasome NRTIs for Improving Insulin Sensitivity and Reducing Type 2 Diabetes Development
Innate immune signaling through the NLRP3 inflammasome is activated by multiple diabetes-related stressors, but whether targeting the inflammasome is beneficial for diabetes is still unclear. Nucleoside reverse-transcriptase inhibitors (NRTI), drugs approved to treat HIV-1 and hepatitis B infections, also block inflammasome activation. Here, we show, by analyzing five health insurance databases, that the adjusted risk of incident diabetes is 33% lower in patients with NRTI exposure among 128,861 patients with HIV-1 or hepatitis B (adjusted hazard ratio for NRTI exposure, 0.673; 95% confidence interval, 0.638 to 0.710; P \u3c 0.0001; 95% prediction interval, 0.618 to 0.734). Meanwhile, an NRTI, lamivudine, improves insulin sensitivity and reduces inflammasome activation in diabetic and insulin resistance-induced human cells, as well as in mice fed with high-fat chow; mechanistically, inflammasome-activating short interspersed nuclear element (SINE) transcripts are elevated, whereas SINE-catabolizing DICER1 is reduced, in diabetic cells and mice. These data suggest the possibility of repurposing an approved class of drugs for prevention of diabetes