4,582 research outputs found
Measuring Renyi Entropy in Neural Network Quantum States
We compute the Renyi entropy in a one-dimensional transverse-field quantum
Ising model by employing a swapping operator acting on the states which are
prepared from the neural network methods. In the static ground state, Renyi
entropy can uncover the critical point of the quantum phase transition from
paramagnetic to ferromagnetic. At the critical point, the relation between the
Renyi entropy and the subsystem size satisfies the predictions from conformal
field theory. In the dynamical case, we find coherent oscillations of the Renyi
entropy after the end of the linear quench. These oscillations have universal
frequencies which may come from the superpositions of excited states. The
asymptotic form of the Renyi entropy implies a new length scale away from the
critical point. This length scale is also verified by the overlap of the
reduced Renyi entropy against the dimensionless subsystem size
The global geometrical property of jet events in high-energy nuclear collisions
We present the first theoretical study of medium modifications of the global
geometrical pattern, i.e., transverse sphericity () distribution of
jet events with parton energy loss in relativistic heavy-ion collisions. In our
investigation, POWHEG+PYTHIA is employed to make an accurate description of
transverse sphericity in the p+p baseline, which combines the next-to-leading
order (NLO) pQCD calculations with the matched parton shower (PS). The Linear
Boltzmann Transport (LBT) model of the parton energy loss is implemented to
simulate the in-medium evolution of jets. We calculate the event normalized
transverse sphericity distribution in central Pb+Pb collisions at the LHC, and
give its medium modifications. An enhancement of transverse sphericity
distribution at small region but a suppression at large
region are observed in A+A collisions as compared to their p+p references,
which indicates that in overall the geometry of jet events in Pb+Pb becomes
more pencil-like. We demonstrate that for events with 2 jets in the final-state
of heavy-ion collisions, the jet quenching makes the geometry more sphere-like
with medium-induced gluon radiation. However, for events with ~jets,
parton energy loss in the QCD medium leads to the events more pencil-like due
to jet number reduction, where less energetic jets may lose their energies and
then fall off the jet selection kinematic cut. These two effects offset each
other and in the end result in more jetty events in heavy-ion collisions
relative to that in p+p.Comment: 9 pages, 9 figure
Distinguishing Computer-generated Graphics from Natural Images Based on Sensor Pattern Noise and Deep Learning
Computer-generated graphics (CGs) are images generated by computer software.
The~rapid development of computer graphics technologies has made it easier to
generate photorealistic computer graphics, and these graphics are quite
difficult to distinguish from natural images (NIs) with the naked eye. In this
paper, we propose a method based on sensor pattern noise (SPN) and deep
learning to distinguish CGs from NIs. Before being fed into our convolutional
neural network (CNN)-based model, these images---CGs and NIs---are clipped into
image patches. Furthermore, three high-pass filters (HPFs) are used to remove
low-frequency signals, which represent the image content. These filters are
also used to reveal the residual signal as well as SPN introduced by the
digital camera device. Different from the traditional methods of distinguishing
CGs from NIs, the proposed method utilizes a five-layer CNN to classify the
input image patches. Based on the classification results of the image patches,
we deploy a majority vote scheme to obtain the classification results for the
full-size images. The~experiments have demonstrated that (1) the proposed
method with three HPFs can achieve better results than that with only one HPF
or no HPF and that (2) the proposed method with three HPFs achieves 100\%
accuracy, although the NIs undergo a JPEG compression with a quality factor of
75.Comment: This paper has been published by Sensors. doi:10.3390/s18041296;
Sensors 2018, 18(4), 129
Holographic topological defects in a ring: role of diverse boundary conditions
We investigate the formation of topological defects in the course of a
dynamical phase transition with different boundary conditions in a ring from
AdS/CFT correspondence. According to the Kibble-Zurek mechanism, quenching the
system across the critical point to symmetry-breaking phase will result in
topological defects -- winding numbers -- in a compact ring. By setting two
different boundary conditions, i.e., Dirichlet and Neumann boundary conditions
for the spatial component of the gauge fields in the AdS boundary, we achieve
the holographic superfluid and holographic superconductor models, respectively.
In the final equilibrium state, different configurations of the order parameter
phases for these two models indicate a persistent superflow in the holographic
superfluid, however, the holographic superconductor lacks this superflow due to
the existence of local gauge fields. The two-point correlation functions of the
order parameter also behave differently. In particular, for holographic
superfluid the correlation function is a cosine function depending on the
winding number. The correlation function for the holographic superconductor,
however, decays rapidly at short distances and vanishes at long distance, due
to the random localities of the gauge fields. These results are consistent with
our theoretical analysis.Comment: 15pages, 4 figures; Contexts improved and references added; Accepted
by JHE
Topologically Protected Metastable States in Classical Dynamics
We propose that the domain walls formed in a classical Ginzburg-Landau model
can exhibit topologically stable but thermodynamically metastable states. This
proposal relies on Allen-Cahn's assertion that the velocity of domain wall at
some point is proportional to the mean curvature at that point. From this
assertion we speculate that domain wall resembles a rubber band that can winds
the background geometry in a nontrivial way and can exist permanently. We
numerically verify our proposal in two and three spatial dimensions by using
periodic boundary conditions as well as Neumann boundary conditions. We find
that there are always possibilities to form topologically stable domain walls
in the final equilibrium states. However, from the aspects of thermodynamics
these topologically nontrivial domain walls have higher free energies and are
thermodynamically metastable. These metastable states that are protected by
topology could potentially serve as storage media in the computer and
information technology industry.Comment: 5 pages, 4 figure
- …