61,695 research outputs found
Bounded perturbation resilience of projected scaled gradient methods
We investigate projected scaled gradient (PSG) methods for convex
minimization problems. These methods perform a descent step along a diagonally
scaled gradient direction followed by a feasibility regaining step via
orthogonal projection onto the constraint set. This constitutes a generalized
algorithmic structure that encompasses as special cases the gradient projection
method, the projected Newton method, the projected Landweber-type methods and
the generalized Expectation-Maximization (EM)-type methods. We prove the
convergence of the PSG methods in the presence of bounded perturbations. This
resilience to bounded perturbations is relevant to the ability to apply the
recently developed superiorization methodology to PSG methods, in particular to
the EM algorithm.Comment: Computational Optimization and Applications, accepted for publicatio
Analyticity of the Susceptibility Function for Unimodal Markovian Maps of the Interval
In a previous note [Ru] the susceptibility function was analyzed for some
examples of maps of the interval. The purpose of the present note is to give a
concise treatment of the general unimodal Markovian case (assuming real
analytic). We hope that it will similarly be possible to analyze maps
satisfying the Collet-Eckmann condition. Eventually, as explained in [Ru],
application of a theorem of Whitney [Wh] should prove differentiability of the
map restricted to a suitable set.Comment: 8 page
Critical behaviours of contact near phase transitions
A central quantity of importance for ultracold atoms is contact, which
measures two-body correlations at short distances in dilute systems. It appears
in universal relations among thermodynamic quantities, such as large momentum
tails, energy, and dynamic structure factors, through the renowned Tan
relations. However, a conceptual question remains open as to whether or not
contact can signify phase transitions that are insensitive to short-range
physics. Here we show that, near a continuous classical or quantum phase
transition, contact exhibits a variety of critical behaviors, including scaling
laws and critical exponents that are uniquely determined by the universality
class of the phase transition and a constant contact per particle. We also use
a prototypical exactly solvable model to demonstrate these critical behaviors
in one-dimensional strongly interacting fermions. Our work establishes an
intrinsic connection between the universality of dilute many-body systems and
universal critical phenomena near a phase transition.Comment: Final version published in Nat. Commun. 5:5140 doi:
10.1038/ncomms6140 (2014
Relation of SiO maser emission to IR radiation in evolved stars based on the MSX observation
Based on the space MSX observation in bands A(8m), C(12m),
D(15m) and E(21m), and the ground SiO maser observation of evolved
stars by the Nobeyama 45-m telescope in the v=1 and v=2 J=1-0 transitions, the
relation between SiO maser emission and mid-IR continuum radiation is analyzed.
The relation between SiO maser emission and the IR radiation in the MSX bands
A, C, D and E is all clearly correlated. The SiO maser emission can be
explained by a radiative pumping mechanism according to its correlation with
infrared radiation in the MSX band A.Comment: 11 pages, 4 figures, to appear in ApJ
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Two novel nonlinear companding schemes with iterative receiver to reduce PAPR in multi-carrier modulation systems
Companding transform is an efficient and simple method to reduce the Peak-to-Average Power Ratio (PAPR) for Multi-Carrier Modulation (MCM) systems. But if the MCM signal is only simply operated by inverse companding transform at the receiver, the resultant spectrum may exhibit severe in-band and out-of-band radiation of the distortion components, and considerable peak regrowth by excessive channel noises etc. In order to prevent these problems from occurring, in this paper, two novel nonlinear companding schemes with a iterative receiver are proposed to reduce the PAPR. By transforming the amplitude or power of the original MCM signals into uniform distributed signals, the novel schemes can effectively reduce PAPR for different modulation formats and sub-carrier sizes. Despite moderate complexity increasing at the receiver, but it is especially suitable to be combined with iterative channel estimation. Computer simulation results show that the proposed schemes can offer good system performances without any bandwidth expansion
Spin relaxation in an InAs quantum dot in the presence of terahertz driving fields
The spin relaxation in a 1D InAs quantum dot with the Rashba spin-orbit
coupling under driving THz magnetic fields is investigated by developing the
kinetic equation with the help of the Floquet-Markov theory, which is
generalized to the system with the spin-orbit coupling, to include both the
strong driving field and the electron-phonon scattering. The spin relaxation
time can be effectively prolonged or shortened by the terahertz magnetic field
depending on the frequency and strength of the terahertz magnetic field. The
effect can be understood as the sideband-modulated spin-phonon scattering. This
offers an additional way to manipulate the spin relaxation time.Comment: 8 pages, 1 figure, to be published in PR
Single chargino production via gluon-gluon fusion in a supersymmetric theory with an explicit R-parity violation
We studied the production of single chargino
accompanied by lepton via gluon-gluon fusion at the LHC. The
numerical analysis of their production rates is carried out in the mSUGRA
scenario with some typical parameter sets. The results show that the cross
sections of the productions via gluon-gluon
collision are in the order of femto barn quantitatively at the
CERN LHC, and can be competitive with production mechanism via quark-antiquark
annihilation process.Comment: LaTex file, 18 pages, 4 EPS file
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