4,749 research outputs found
Non-Fermi-Liquid/Marginal-Fermi-Liquid Signatures Induced by Van Hove Singularity
We theoretically study the two-dimensional metal that is coupled to critical
magnons and features van Hove singularities on the Fermi surface. When there is
only translationally invariant SYK-liked Yukawa interaction, van Hove points
suppress the contribution from the part of the Fermi surface away from them,
dominating and exhibiting non-Fermi-liquid behavior. When introducing
disordered Yukawa coupling, it leads to a crossover from non-Fermi-liquid to
marginal-Fermi-liquid, and the marginal-Fermi-liquid region exhibits the specific heat and temperature-linear resistivity of strange metal. By
solving the gap equation, we provide the critical temperature for
superconductor induced by van Hove singularities and point out the possible
emergence of pair-density-wave superconductor. Our theory may become a new
mechanism for understanding non-Fermi-liquid or marginal-Fermi-liquid
phenomenons.Comment: 14 pages, 5 figure
GeV {\gamma}-ray Emission Detected by Fermi-LAT Probably Associated with the Thermal Composite Supernova Remnant Kesteven 41 in a Molecular Environment
Hadron emission from supernova remnant (SNR)-molecular cloud (MC) association
systems has been widely regarded as a probe of the shock-accelerated cosmic-ray
protons. Here, we report on the detection of a {\gamma}-ray emission source,
with a significance of 24{\sigma} in 0.2-300 GeV, projected to lie to the
northwest of the thermal composite SNR Kesteven 41, using 5.6 years of
Fermi-Large Area Telescope (LAT) observation data. No significant long-term
variability in the energy range 0.2--300 GeV is detected around this source.
The 3{\sigma} error circle, 0.09 degree; in radius, covers the 1720MHz OH maser
and is essentially consistent with the location of the V_{LSR} ~-50 km/s MC
with which the SNR interacts. The source emission has an exponential cutoff
power-law spectrum with a photon index of 1.9+/-0.1 and a cutoff energy of
4.0+/-0.9 GeV, and the corresponding 0.2-300 GeV luminosity is ~1.3*10^36 erg/s
at a distance of 12 kpc. There is no radio pulsar in the 3{\sigma} circle
responsible for the high {\gamma}-ray luminosity. While the inverse Compton
scattering scenario would lead to a difficulty in the electron energy budget,
the source emission can naturally be explained by the hadronic interaction
between the relativistic protons accelerated by the shock of SNR Kesteven 41
and the adjacent northwestern MC. In this paper, we present a list of Galactic
thermal composite SNRs detected at GeV {\gamma}-ray energies by Fermi-LAT is
presented
Careful at Estimation and Bold at Exploration
Exploration strategies in continuous action space are often heuristic due to
the infinite actions, and these kinds of methods cannot derive a general
conclusion. In prior work, it has been shown that policy-based exploration is
beneficial for continuous action space in deterministic policy reinforcement
learning(DPRL). However, policy-based exploration in DPRL has two prominent
issues: aimless exploration and policy divergence, and the policy gradient for
exploration is only sometimes helpful due to inaccurate estimation. Based on
the double-Q function framework, we introduce a novel exploration strategy to
mitigate these issues, separate from the policy gradient. We first propose the
greedy Q softmax update schema for Q value update. The expected Q value is
derived by weighted summing the conservative Q value over actions, and the
weight is the corresponding greedy Q value. Greedy Q takes the maximum value of
the two Q functions, and conservative Q takes the minimum value of the two
different Q functions. For practicality, this theoretical basis is then
extended to allow us to combine action exploration with the Q value update,
except for the premise that we have a surrogate policy that behaves like this
exploration policy. In practice, we construct such an exploration policy with a
few sampled actions, and to meet the premise, we learn such a surrogate policy
by minimizing the KL divergence between the target policy and the exploration
policy constructed by the conservative Q. We evaluate our method on the Mujoco
benchmark and demonstrate superior performance compared to previous
state-of-the-art methods across various environments, particularly in the most
complex Humanoid environment.Comment: 20 page
Unified Detoxifying and Debiasing in Language Generation via Inference-time Adaptive Optimization
Warning: this paper contains model outputs exhibiting offensiveness and
biases. Recently pre-trained language models (PLMs) have prospered in various
natural language generation (NLG) tasks due to their ability to generate fairly
fluent text. Nevertheless, these models are observed to capture and reproduce
harmful contents in training corpora, typically toxic language and social
biases, raising severe moral issues. Prior works on ethical NLG tackle
detoxifying and debiasing separately, which is problematic since we find
debiased models still exhibit toxicity while detoxified ones even exacerbate
biases. To address such a challenge, we propose the first unified framework of
detoxifying and debiasing called UDDIA, which jointly formalizes these two
problems as rectifying the output space. We theoretically interpret our
framework as learning a text distribution mixing weighted attributes. Besides,
UDDIA conducts adaptive optimization of only a few parameters during decoding
based on a parameter-efficient tuning schema without any training data. This
leads to minimal generation quality loss and improved rectification performance
with acceptable computational cost. Experimental results demonstrate that
compared to several strong baselines, UDDIA achieves debiasing and detoxifying
simultaneously and better balances efficiency and effectiveness, taking a
further step towards practical ethical NLG.Comment: Work in Progress. Preprin
Critical Behavior and Duality in Dimensionally Reduced Planar Chern-Simons Superconductors
Tha quantum electrodynamics of particles constrained to move on a plane is
not a fully dimensionally reduced theory because the gauge fields through which
they interact live in higher dimensions. By constraining the gauge field to the
surface of the bulk, we obtain a fully reduced planar Abelian Chern-Simons
Higgs model that can describe the vortex dynamics and second-order
superconducting-normal phase transitions in planar Chern-Simons
superconductors. Dual analyses performed before and after dimensional reduction
yield the same Lagrangian for describing the vortex dynamics, indicating the
self-consistency of our reduced theory. Compared to ordinary (2+1)-dimensional
electrodynamics, we obtain anomalous fermion statistical vortices, consistent
with results considering boundary effects. An additional electric charge
constraint and different Chern-Simons parameter constraints are also found,
which may help define a self-dual conformal field theory. Our renormalization
group analysis shows that the quantized critical exponent depends on the
Chern-Simons parameter. Quench disorder can bring more stable fixed points with
different dynamical critical exponents. If we dimensionally reduce to a curved
surface, our theory can also be extended to curved spacetimes, where geometric
flow will be introduced and compete with vortex flow.Comment: 17 pages, 8 figure
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