8,183 research outputs found
Effective Low-Energy Model for f-Electron Delocalization
We consider a Periodic Anderson Model (PAM) with a momentum-dependent
inter-band hybridization that is strongly suppressed near the Fermi level.
Under these conditions, we reduce the PAM to an effective low-energy
Hamiltonian, , by expanding in the small parameter (
is the maximum inter-band hybridization amplitude and is the hopping
integral of the broad band). The resulting model consists of a t-J f-band
coupled via the Kondo exchange to the electrons in the broad band. allows for studying the f-electron delocalization transition. The result
is a doping-induced Mott transition for the f-electron delocalization, which we
demonstrate by density-matrix renormalization group (DMRG) calculations
Experimentally realizable control fields in quantum Lyapunov control
As a hybrid of techniques from open-loop and feedback control, Lyapunov
control has the advantage that it is free from the measurement-induced
decoherence but it includes the system's instantaneous message in the control
loop. Often, the Lyapunov control is confronted with time delay in the control
fields and difficulty in practical implementations of the control. In this
paper, we study the effect of time-delay on the Lyapunov control, and explore
the possibility of replacing the control field with a pulse train or a
bang-bang signal. The efficiency of the Lyapunov control is also presented
through examining the convergence time of the controlled system. These results
suggest that the Lyapunov control is robust gainst time delay, easy to realize
and effective for high-dimensional quantum systems
A New Biometric Template Protection using Random Orthonormal Projection and Fuzzy Commitment
Biometric template protection is one of most essential parts in putting a
biometric-based authentication system into practice. There have been many
researches proposing different solutions to secure biometric templates of
users. They can be categorized into two approaches: feature transformation and
biometric cryptosystem. However, no one single template protection approach can
satisfy all the requirements of a secure biometric-based authentication system.
In this work, we will propose a novel hybrid biometric template protection
which takes benefits of both approaches while preventing their limitations. The
experiments demonstrate that the performance of the system can be maintained
with the support of a new random orthonormal project technique, which reduces
the computational complexity while preserving the accuracy. Meanwhile, the
security of biometric templates is guaranteed by employing fuzzy commitment
protocol.Comment: 11 pages, 6 figures, accepted for IMCOM 201
Testing the Bell Inequality at Experiments of High Energy Physics
Besides using the laser beam, it is very tempting to directly testify the
Bell inequality at high energy experiments where the spin correlation is
exactly what the original Bell inequality investigates. In this work, we follow
the proposal raised in literature and use the successive decays
to testify
the Bell inequality. Our goal is twofold, namely, we first make a Monte-Carlo
simulation of the processes based on the quantum field theory (QFT). Since the
underlying theory is QFT, it implies that we pre-admit the validity of quantum
picture. Even though the QFT is true, we need to find how big the database
should be, so that we can clearly show deviations of the correlation from the
Bell inequality determined by the local hidden variable theory. There have been
some critiques on the proposed method, so in the second part, we suggest some
improvements which may help to remedy the ambiguities indicated by the
critiques. It may be realized at an updated facility of high energy physics,
such as BES III.Comment: 16 pages, 5 figure
Two Time-Scale Caching Placement and User Association in Dynamic Cellular Networks
With the rapid growth of data traffic in cellular networks, edge caching has become an emerging technology for traffic offloading. We investigate the caching placement and content delivery in cache-enabling cellular networks. To cope with the time-varying content popularity and user location in practical scenarios, we formulate a long-term joint dynamic optimization problem of caching placement and user association for minimizing the content delivery delay which considers both content transmission delay and content update delay. To solve this challenging problem, we decompose the optimization problem into two sub-problems, the user association sub-problem in a short time scale and the caching placement in a long time scale. Specifically, we propose a low complexity user association algorithm for a given caching placement in the short time scale. Then we develop a deep deterministic policy gradient based caching placement algorithm which involves the short time-scale user association decisions in the long time scale. Finally, we propose a joint user association and caching placement algorithm to obtain a sub-optimal solution for the proposed problem. We illustrate the convergence and performance of the proposed algorithm by simulation results. Simulation results show that compared with the benchmark algorithms, the proposed algorithm reduces the long-term content delivery delay in dynamic networks effectively
Heavy fermions and two loop electroweak corrections to
Applying effective Lagrangian method and on-shell scheme, we analyze the
electroweak corrections to the rare decay from some
special two loop diagrams in which a closed heavy fermion loop is attached to
the virtual charged gauge bosons or Higgs. At the decoupling limit where the
virtual fermions in inner loop are much heavier than the electroweak scale, we
verify the final results satisfying the decoupling theorem explicitly when the
interactions among Higgs and heavy fermions do not contain the nondecoupling
couplings. Adopting the universal assumptions on the relevant couplings and
mass spectrum of new physics, we find that the relative corrections from those
two loop diagrams to the SM theoretical prediction on the branching ratio of
can reach 5% as the energy scale of new physics
GeV.Comment: 30 pages,4 figure
Mapping the real space distributions of galaxies in SDSS DR7: I. Two Point Correlation Functions
Using a method to correct redshift space distortion (RSD) for individual
galaxies, we mapped the real space distributions of galaxies in the Sloan
Digital Sky Survey (SDSS) Data Release 7 (DR7). We use an ensemble of mock
catalogs to demonstrate the reliability of our method. Here as the first paper
in a series, we mainly focus on the two point correlation function (2PCF) of
galaxies. Overall the 2PCF measured in the reconstructed real space for
galaxies brighter than agrees with the direct
measurement to an accuracy better than the measurement error due to cosmic
variance, if the reconstruction uses the correct cosmology. Applying the method
to the SDSS DR7, we construct a real space version of the main galaxy catalog,
which contains 396,068 galaxies in the North Galactic Cap with redshifts in the
range . The Sloan Great Wall, the largest known
structure in the nearby Universe, is not as dominant an over-dense structure as
appears to be in redshift space. We measure the 2PCFs in reconstructed real
space for galaxies of different luminosities and colors. All of them show clear
deviations from single power-law forms, and reveal clear transitions from
1-halo to 2-halo terms. A comparison with the corresponding 2PCFs in redshift
space nicely demonstrates how RSDs boost the clustering power on large scales
(by about at scales ) and suppress it on
small scales (by about at a scale of ).Comment: 19 pages, 13 figure
Influence of the Magnetic Coupling Process on the Advection Dominated Accretion Flows around Black Holes
A large-scale closed magnetic field can transfer angular momentum and energy
between a black hole (BH) and its surrounding accretion flow. We investigate
the effects of this magnetic coupling (MC) process on the dynamics of a hot
accretion flow (e.g., an advection dominated accretion flow, hereafter ADAF).
The energy and angular momentum fluxes transported by the magnetic field are
derived by an equivalent circuit approach. For a rapidly rotating BH, it is
found that the radial velocity and the electron temperature of the accretion
flow decrease, whereas the ion temperature and the surface density increase.
The significance of the MC effects depends on the value of the viscous
parameter \alpha. The effects are obvious for \alpha=0.3 but nearly ignorable
for \alpha=0.1. For a BH with specific angular momentum, a_*=0.9, and
\alpha=0.3, we find that for reasonable parameters the radiative efficiency of
a hot accretion flow can be increased by about 30%.Comment: 21 pages, 7 figures. Changed after the referee's suggestions.
Accepted for publication in the Astrophysical Journa
Mapping the Real Space Distributions of Galaxies in SDSS DR7: II. Measuring the growth rate, clustering amplitude of matter and biases of galaxies at redshift
We extend the real-space mapping method developed in Shi et at. (2016) so
that it can be applied to flux-limited galaxy samples. We use an ensemble of
mock catalogs to demonstrate the reliability of this extension, showing that it
allows for an accurate recovery of the real-space correlation functions and
galaxy biases. We also demonstrate that, using an iterative method applied to
intermediate-scale clustering data, we can obtain an unbiased estimate of the
growth rate of structure , which is related to the clustering
amplitude of matter, to an accuracy of . Applying this method to the
Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7), we construct a real-space
galaxy catalog spanning the redshift range , which
contains 584,473 galaxies in the north Galactic cap (NGC). Using this data, we
infer \fss at a median redshift , which is consistent with the WMAP9
cosmology at the level. By combining this measurement with the
real-space clustering of galaxies and with galaxy-galaxy weak lensing
measurements for the same sets of galaxies, we are able to break the degeneracy
between , , and . From the SDSS DR7 data alone, we obtain the
following cosmological constraints at redshift :
, , and
, ,
, and for galaxies within
different absolute magnitude bins and , respectively
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