258 research outputs found
Comparing mixing times on sparse random graphs
It is natural to expect that nonbacktracking random walk will mix faster than
simple random walks, but so far this has only been proved in regular graphs. To
analyze typical irregular graphs, let be a random graph on vertices
with minimum degree 3 and a degree distribution that has exponential tails. We
determine the precise worst-case mixing time for simple random walk on , and
show that, with high probability, it exhibits cutoff at time , where is the asymptotic entropy for simple random walk on
a Galton--Watson tree that approximates locally. (Previously this was only
known for typical starting points.) Furthermore, we show that this asymptotic
mixing time is strictly larger than the mixing time of nonbacktracking walk,
via a delicate comparison of entropies on the Galton-Watson tree
Navigating Cultural Chasms: Exploring and Unlocking the Cultural POV of Text-To-Image Models
Text-To-Image (TTI) models, such as DALL-E and StableDiffusion, have
demonstrated remarkable prompt-based image generation capabilities.
Multilingual encoders may have a substantial impact on the cultural agency of
these models, as language is a conduit of culture. In this study, we explore
the cultural perception embedded in TTI models by characterizing culture across
three hierarchical tiers: cultural dimensions, cultural domains, and cultural
concepts. Based on this ontology, we derive prompt templates to unlock the
cultural knowledge in TTI models, and propose a comprehensive suite of
evaluation techniques, including intrinsic evaluations using the CLIP space,
extrinsic evaluations with a Visual-Question-Answer (VQA) model and human
assessments, to evaluate the cultural content of TTI-generated images. To
bolster our research, we introduce the CulText2I dataset, derived from four
diverse TTI models and spanning ten languages. Our experiments provide insights
regarding Do, What, Which and How research questions about the nature of
cultural encoding in TTI models, paving the way for cross-cultural applications
of these models
Magnetic Monopole Noise
Magnetic monopoles are hypothetical elementary particles exhibiting quantized
magnetic charge and quantized magnetic flux . A classic proposal for detecting such magnetic charges is to measure the
quantized jump in magnetic flux threading the loop of a superconducting
quantum interference device (SQUID) when a monopole passes through it.
Naturally, with the theoretical discovery that a plasma of emergent magnetic
charges should exist in several lanthanide-pyrochlore magnetic insulators,
including DyTiO, this SQUID technique was proposed for their direct
detection. Experimentally, this has proven extremely challenging because of the
high number density, and the generation-recombination (GR) fluctuations, of the
monopole plasma. Recently, however, theoretical advances have allowed the
spectral density of magnetic-flux noise due to GR
fluctuations of magnetic charge pairs to be determined. These
theories present a sequence of strikingly clear predictions for the
magnetic-flux noise signature of emergent magnetic monopoles. Here we report
development of a high-sensitivity, SQUID based flux-noise spectrometer, and
consequent measurements of the frequency and temperature dependence of
for DyTiO samples. Virtually all the elements
of predicted for a magnetic monopole plasma, including the
existence of intense magnetization noise and its characteristic frequency and
temperature dependence, are detected directly. Moreover, comparisons of
simulated and measured correlation functions of the magnetic-flux
noise imply that the motion of magnetic charges is strongly
correlated because traversal of the same trajectory by two magnetic charges of
same sign is forbidden
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