689 research outputs found
Photon regions, shadow observables and constraints from M87* of a charged rotating black hole
Inspired by the observations of supermassive black hole M87* in \emph{Event
Horizon Telescope }(EHT) experiment, a remarkable surge in black hole physics
is to use the black hole shadow's observables to distinguish general relativity
(GR) and modified theories of gravity (MoG), which could also help to disclose
the astrophysical nature of the center black hole in EHT observation. In this
paper, we shall extensively carry out the study of a charged rotating black
hole in conformal gravity, in which the term related with the charge has
different falloffs from the usual Kerr-Newman (KN) black hole. We investigate
the spacetime properties including the horizons, ergospheres and the photon
regions; afterward, we show the boundary of black hole shadow and investigate
its characterized observables. The features closely depend on the spin and
charge parameters, which are compared with those in Kerr and KN black holes.
Then presupposing the M87* a charged rotating black hole in conformal gravity,
we also constrain the black hole parameters via the observation constraints
from EHT experiment. We find that the constraints on the inferred circularity
deviation, , and on the shadow axial ratio, , for the M87* black hole are satisfied for the entire parameter
space of the charged rotating black hole in conformal gravity. However, the
shadow angular diameter will give upper bound on
the parameter space. Our findings indicate that the current charged rotating
black hole in conformal gravity could be a candidate for astrophysical black
holes. Moreover, the EHT observation on the axial ratio may help us to
distinguish Kerr black hole and the current charged rotating black hole in
conformal gravity in some parameter space.Comment: references adde
Low-depth Hamiltonian Simulation by Adaptive Product Formula
Various Hamiltonian simulation algorithms have been proposed to efficiently
study the dynamics of quantum systems using a universal quantum computer.
However, existing algorithms generally approximate the entire time evolution
operators, which may need a deep quantum circuit that are beyond the capability
of near-term noisy quantum devices. Here, focusing on the time evolution of a
fixed input quantum state, we propose an adaptive approach to construct a
low-depth time evolution circuit. By introducing a measurable quantifier that
describes the simulation error, we use an adaptive strategy to learn the
shallow quantum circuit that minimizes the simulation error. We numerically
test the adaptive method with the electronic Hamiltonians of
and molecules, and the transverse field ising model with random
coefficients. Compared to the first-order Suzuki-Trotter product formula, our
method can significantly reduce the circuit depth (specifically the number of
two-qubit gates) by around two orders while maintaining the simulation
accuracy. We show applications of the method in simulating many-body dynamics
and solving energy spectra with the quantum Krylov algorithm. Our work sheds
light on practical Hamiltonian simulation with noisy-intermediate-scale-quantum
devices.Comment: 10 pages, 2 figure
Dirac fermions with plaquette interactions. III. SU(N) phase diagram with Gross-Neveu criticality and first-order phase transition
Inspired by our recent works[1, 2] of SU(2) and SU(4) Dirac fermions
subjected to plaquette interactions on square lattice, here we extend the
large-scale quantum Monte Carlo investigations to the phase digram of
correlated Dirac fermions with SU(6) and SU(8) symmetries subjected to the
plaquette interaction on the same lattice. From SU(2) to SU(8), the rich phase
diagram exhibits a plethora of emerging quantum phases such as the Dirac
semimetal, the antiferromagnetic Mott insulator, valence bond solid (VBS) and
the Dirac spin liquid and phase transitions including the Gross-Neveu chiral
transitions with emergent continuous symmetry, the deconfined quantum
criticality and the first order transition between interaction-driven columnar
VBS and plaquette VBS. These rich phenomena coming from the simple-looking
lattice models, firmly convey the message that the interplay between the
Dirac fermions -- with enhanced internal symmetries -- and extended
plaquette interactions -- beyond the on-site Hubbard type -- is the new
playground to synthesise novel highly entangled quantum matter both at the
model level and with experimental feasibilities.Comment: 9 pages, 7 figure
Dirac fermions with plaquette interactions. I. SU(2) phase diagram with Gross-Neveu and deconfined quantum criticalities
We investigate the ground state phase diagram of an extended Hubbard model
with -flux hopping term at half-filling on a square lattice, with unbiased
large-scale auxiliary-field quantum Monte Carlo simulations. As a function of
interaction strength, there emerges an intermediate phase which realizes two
interaction-driven quantum critical points, with the first between the Dirac
semimetal and an insulating phase of weak valence bond solid (VBS) order, and
the second separating the VBS order and an antiferromagnetic insulating phase.
These intriguing quantum critical points are respectively bestowed with
Gross-Neveu and deconfined quantum criticalities, and the critical exponents
and at deconfined quantum
critical point satisfy the CFT Bootstrap bound. We also investigate the
dynamical properties of the spin excitation and find the spin gap open near the
first transition and close at the second. The relevance of our findings in
realizing deconfined quantum criticality in fermion systems and the implication
to lattice models with further extended interactions such as those in quantum
Moir\'e systems, are discussed.Comment: 6+2 pages, 5+2 figure
Caution on Gross-Neveu criticality with a single Dirac cone: Violation of locality and its consequence of unexpected finite-temperature transition
Lately there are many SLAC fermion investigations on the (2+1)D Gross-Neveu
criticality of a single Dirac cone [1,2]. While the SLAC fermion construction
indeed gives rise to the linear energy-momentum relation for all lattice
momenta at the non-interacting limit, the long-range hopping and its consequent
violation of locality on the Gross-Neveu quantum critical point (GN-QCP) --
which a priori requires short-range interaction -- has not been verified. Here
we show, by means of large-scale quantum Monte Carlo simulations, that the
interaction-driven antiferromagnetic insulator in this case is fundamentally
different from that on a purely local -flux Hubbard model on the square
lattice. In particular, we find the antiferromagnetic long-range order in the
SLAC fermion model has a finite temperature continuous phase transition, which
violates the Mermin-Wagner theorem, and smoothly connects to the previously
determined GN-QCP. The magnetic excitations inside the antiferromagnetic
insulator are gapped without Goldstone mode, even though the state
spontaneously breaks continuous symmetry. These unusual results
proclaim caution on the interpretation of the quantum phase transition in SLAC
fermion model as that of GN-QCP with short-range interaction
Postweaning Isolation Rearing Alters the Adult Social, Sexual Preference and Mating Behaviors of Male CD-1 Mice
Objective: No study has comprehensively evaluated the effect of postweaning isolation on the social and sexual behaviors of a certain strain of rodents in ethology. The present study aims to explore how and to what extent isolation rearing after postweaning affects the social and sexual behaviors of male CD-1 mice in adulthood systematically.Methods: Male CD-1 mice were randomly assigned to two groups: isolation reared (IS, one mouse per cage, n = 30) and group housed (GH, five mice per cage, n = 15). The mice underwent isolation rearing from postnatal day 23 to day 93. Then, social affiliation, recognition and memory were measured through selection task experiments. Social interaction under a home cage and novel environment were measured via resident–intruder and social interaction test, respectively. Furthermore, sexual preference, homosexual and heterosexual behaviors were measured.Results: Our study found that postweaning isolation increased the social affiliation for conspecifics (p = 0.001), reduced social recognition (p = 0.042) and impaired social memory. As for social interaction, isolated mice showed a remarkably increased aggression toward the intruder male in a home cage or novelty environment. For instance, isolated mice presented a short attack latency (p < 0.001), high attack frequency (p < 0.001) and long attack duration (p < 0.001). In addition, isolated mice exhibited further social avoidance. Contrastingly, isolated mice displayed a reduced sexual preference for female (IS: 61.47 ± 13.80%, GH: 70.33 ± 10.06%, p = 0.038). As for heterosexual behavior, isolated mice have a short mating duration (p = 0.002), long mounting latency (p = 0.002), and long intromission latency (p = 0.015). However, no association was observed between postweaning isolation and homosexual behavior in male CD-1 mouse.Conclusion: Postweaning isolation increased the social affiliation, impaired the social cognition and considerably increased the aggression in social interaction of adult male CD-1 mice. Postweaning isolation induced a decreased sexual preference for female in adulthood. Postweaning isolation extended the latency to mate, thereby reducing mating behavior. No association was observed between isolation and homosexual behavior
Traditional Wooden Buildings in China
Chinese ancient architecture, with its long history, unique systematic features and wide-spread employment as well as its abundant heritages, is a valuable legacy of the whole world. Due to the particularity of the material and structure of Chinese ancient architecture, relatively research results are mostly published in Chinese, which limits international communication. On account of the studies carried out in Nanjing Forestry University and many other universities and teams, this chapter emphatically introduces the development, structural evolution and preservation of traditional Chinese wooden structure; research status focuses on material properties, decay pattern, anti-seismic performance and corresponding conservation and reinforcement technologies of the main load-bearing members in traditional Chinese wooden structure
Degradation Mechanisms and Mitigation Strategies of Nickel-Rich NMC-Based Lithium-Ion Batteries
Abstract
The demand for lithium-ion batteries (LIBs) with high mass-specific capacities, high rate capabilities and long-term cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNixMnyCo1−x−yO2, x⩾0.5) cathodes and graphite (LixC6) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid electrolyte interfaces are also reviewed, and trade-offs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.
Graphic Abstract
The demand for lithium-ion batteries (LIBs) with high mass specific capacities, high rate capabilities and longterm cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNixMnyCo1−x−yO2, x ≥ 0.5) cathodes and graphite (LixC6) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid-electrolyte interfaces (SEIs) are also reviewed and tradeoffs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions
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