511 research outputs found
Using LISA-like Gravitational Wave Detectors to Search for Primordial Black Holes
Primordial black hole (PBH), which can be naturally produced in the early
universe, remains a promising dark matter candidate . It can merge with a
supermassive black hole (SMBH) in the center of a galaxy and generate
gravitational wave (GW) signals in the favored frequency region of LISA-like
experiments. In this work, we initiate the study on the event rate calculation
for such extreme mass ratio inspirals (EMRI). Including the sensitivities of
various proposed GW detectors, we find that such experiments offer a novel and
outstanding tool to test the scenario where PBH constitutes (fraction of) dark
matter. The PBH energy density fraction of DM () could
potentially be explored as small as . Further, LISA has
the capability to search for PBH mass upto .
Other proposed GW experiments can probe lower PBH mass regime.Comment: 8 pages, 2 figure
Electron Flavored Dark Matter
In this paper we investigate the phenomenology of the electron flavored Dirac
dark matter with two types of portal interactions. We analyze constraints from
the electron magnetic moment anomaly, LHC searches of singly charged scalar,
dark matter relic abundance as well as direct and indirect detections. Our
study shows that the available parameter space is quite constrained, but there
are parameter space that is compatible with the current data. We further show
that the DAMPE cosmic ray electron excess, which indicates cosmic ray excess at
around 1.5 TeV, can be interpreted as the annihilation of dark matter into
electron positron pairs in this model.Comment: 6 pages, 5 figure
Unconventional Superconducting Symmetry in a Checkerboard Antiferromagnet
We use a renormalized mean field theory to study the Gutzwiller projected BCS
states of the extended Hubbard model in the large limit, or the
--- model on a two-dimensional checkerboard lattice. At small
, the frustration due to the diagonal terms of and does not
alter the -wave pairing symmetry, and the negative (positive)
enhances (suppresses) the pairing order parameter. At large , the
ground state has an extended s-wave symmetry. At the intermediate , the
ground state is or -wave with time reversal symmetry broken.Comment: 6 pages, 6 figure
Oscillations of Ultralight Dark Photon into Gravitational Waves
The discovery of gravitational waves (GWs) opens a new window for exploring
the physics of the early universe. Identifying the source of GWs and their
spectra today turn out to be the important tasks so as to assist the
experimental detection of stochastic GWs. In this paper, we investigate the
oscillations of the ultralight dark photon (ULDP) into GWs in the dark halo.
Assuming dark matter is composed of the ULDP and there are primordial dark
magnetic fields (PDMFs) arising from the axion inflation and/or the dark phase
transition, then the ULDP can oscillate into the GW when it passes through an
environment of PDMFs. We derive the local energy density of GWs in the galaxy
cluster induced by the instaneous oscillation of ULDP in the PDMFs. These
stochastic local GWs exhibit a pulse-like spectrum, with frequency depending on
the mass of the ULDP, and can be detected in Pulsar Timing Arrays (PTAs) or
future space-based interferometers. We also find that the low-frequency GW
signal observed by the NANOGrav collaboration and other PTA experiments can be
explained by the oscillation of the ULDP in the PDMFs in the early universe.Comment: 7 pages, 3 figure
Quantum speed limit for complex dynamics
Quantum speed limit focuses on the minimum time scale for a fixed mission and
hence is important in quantum information where fast dynamics is usually
beneficial. Recently an operational definition of quantum speed limit (OQSL)
was proposed, which reveals the intrinsic minimum time for time-independent
Hamiltonians. However, a general method to evaluate the OQSL for time-dependent
Hamiltonians, especially when noises are involved, is still in lack. Hereby we
provide the expression of OQSL for a certain type of time-dependent
Hamiltonians and propose a three-step (classification-regression-calibration)
methodology based on machine learning for the evaluation of OQSL in complex
dynamics.Comment: 24 pages, 14 figures, 1 tabl
A Multi-Agent-Based System for eProcurement
E-procurement has become an important function of enterprise information systems. The process of e-procurement includes automatic definition of product requirements, search and selection for suppliers, negotiation and contracting with suppliers. In this paper, we propose a novel agentbased architecture for e-procurement system, in which various agents take such responsibilities as negotiating and contracting. Moreover, the architecture that we propose can monitor transaction status and enhance the flexibility to handle unexpected exceptions, thus leading to agile procurement management
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