4,314 research outputs found
Voter model on a directed network: Role of bidirectional opinion exchanges
The voter model with the node update rule is numerically investigated on a
directed network. We start from a directed hierarchical tree, and split and
rewire each incoming arc at the probability . In order to discriminate the
better and worse opinions, we break the symmetry () by
giving a little more preference to the opinion . It is found that
as becomes larger, introducing more complicated pattern of information flow
channels, and as the network size becomes larger, the system eventually
evolves to the state in which more voters agree on the better opinion, even
though the voter at the top of the hierarchy keeps the worse opinion. We also
find that the pure hierarchical tree makes opinion agreement very fast, while
the final absorbing state can easily be influenced by voters at the higher
ranks. On the other hand, although the ordering occurs much slower, the
existence of complicated pattern of bidirectional information flow allows the
system to agree on the better opinion.Comment: 5 pages, 3 figures, Phys. Rev. E (in press
Double resonance in the infinite-range quantum Ising model
We study quantum resonance behavior of the infinite-range kinetic Ising model
at zero temperature. Numerical integration of the time-dependent Schr\"odinger
equation in the presence of an external magnetic field in the direction is
performed at various transverse field strengths . It is revealed that two
resonance peaks occur when the energy gap matches the external driving
frequency at two distinct values of , one below and the other above the
quantum phase transition. From the similar observations already made in
classical systems with phase transitions, we propose that the double resonance
peaks should be a generic feature of continuous transitions, for both quantum
and classical many-body systems.Comment: 4 pages, 5 figure
Audio-Visual Spatial Integration and Recursive Attention for Robust Sound Source Localization
The objective of the sound source localization task is to enable machines to
detect the location of sound-making objects within a visual scene. While the
audio modality provides spatial cues to locate the sound source, existing
approaches only use audio as an auxiliary role to compare spatial regions of
the visual modality. Humans, on the other hand, utilize both audio and visual
modalities as spatial cues to locate sound sources. In this paper, we propose
an audio-visual spatial integration network that integrates spatial cues from
both modalities to mimic human behavior when detecting sound-making objects.
Additionally, we introduce a recursive attention network to mimic human
behavior of iterative focusing on objects, resulting in more accurate attention
regions. To effectively encode spatial information from both modalities, we
propose audio-visual pair matching loss and spatial region alignment loss. By
utilizing the spatial cues of audio-visual modalities and recursively focusing
objects, our method can perform more robust sound source localization.
Comprehensive experimental results on the Flickr SoundNet and VGG-Sound Source
datasets demonstrate the superiority of our proposed method over existing
approaches. Our code is available at: https://github.com/VisualAIKHU/SIRA-SSLComment: Camera-Ready, ACM MM 202
Phonon arithmetic in a trapped ion system
Single-quantum level operations are important tools to manipulate a quantum state. Annihilation or creation of single particles translates a quantum state to another by adding or subtracting a particle, depending on how many are already in the given state. The operations are probabilistic and the success rate has yet been low in their experimental realization. Here we experimentally demonstrate (near) deterministic addition and subtraction of a bosonic particle, in particular a phonon of ionic motion in a harmonic potential. We realize the operations by coupling phonons to an auxiliary two-level system and applying transitionless adiabatic passage. We show handy repetition of the operations on various initial states and demonstrate by the reconstruction of the density matrices that the operations preserve coherences. We observe the transformation of a classical state to a highly non-classical one and a Gaussian state to a non-Gaussian one by applying a sequence of operations deterministically
Unruh effect of nonlocal field theories with a minimal length
The nonlocal field theory commonly requires a minimal length, and so it
appears to formulate the nonlocal theory in terms of the doubly special
relativity which makes the speed of light and the minimal length invariant
simultaneously. We set up a generic nonlocal model having the same set of
solutions as the local theory but allowing Lorentz violations due to the
minimal length. It is exactly corresponding to the model with the modified
dispersion relation in the doubly special relativity. For this model, we
calculate the modified Wightman function and the rate of response function by
using the Unruh-DeWitt detector method. It turns out that the Unruh effect
should be corrected by the minimal length related to the nonlocality in the
regime of the doubly special relativity. However, for the Lorentz-invariant
limit, it is shown that the Wightman function and the Unruh effect remain the
same as those of the local theory.Comment: 16 pages, version to appear in PL
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