132,720 research outputs found

### Current collection in an anisotropic plasma

A general method is given to derive the current-potential relations in anisotropic plasmas. Orbit limit current is assumed. The collector is a conductive sphere or an infinite cylinder. Any distribution which is an arbitrary function of the velocity vector can be considered as a superposition of many mono-energetic beams whose current-potential relations are known. The results for two typical pitch angle distributions are derived and discussed in detail. The general properties of the current potential relations are very similar to that of a Maxwellian plasma except for an effective temperature which varies with the angle between the magnetic field and the charging surface. The conclusions are meaningful to generalized geometries

### Partial Differential Chow Forms and a Type of Partial Differential Chow varieties

We first present an intersection theory of partial differential varieties
with quasi-generic differential hypersurfaces. Then based on the generic
intersection theory, we define the partial differential Chow form for an
irreducible partial differential variety $V$ of Kolchin polynomial
$\omega_V(t)=(d+1){t+m\choose m}-{t+m-s\choose m}$. And we establish for the
partial differential Chow form most of the basic properties of the ordinary
differential Chow form. Furthermore, we prove the existence of a type of
partial differential Chow varieties.Comment: 30 page

### Observation of a "Ridge" correlation structure in high multiplicity proton-proton collisions: A brief review

This paper briefly reviews the striking experimental observation of a
ridge-like dihadron correlation structure in high multiplicity proton-proton
collisions at the Large Hadron Collider (LHC). Recent progress of both
experimental and theoretical efforts on understanding the physical origin of
the novel effect is reviewed. Outlook on future direction of possible new
studies is discussed.Comment: 16 pages, 12 figures, brief review for Modern Physics Letter

### System size dependence of two-particle angular correlations in p+p, Cu+Cu and Au+Au collisions

We present a systematic study of two-particle angular correlations in p+p,
Cu+Cu and Au+Au collisions over a broad range of pseudorapidity and azimuthal
angle. The PHOBOS detector has a uniquely large angular coverage for inclusive
charged particles, which allows for the study of correlations on both long- and
short-range scales. A complex two-dimensional correlation structure emerges
which is interpreted in the context of a cluster model. The cluster size and
its decay width are extracted from the two-particle pseudorapidity correlation
function. The cluster size found in semi-central Cu+Cu and Au+Au collisions is
comparable to that found in p+p but a non-trivial increase of cluster size with
decreasing centrality is observed. Moreover, the comparison between Cu+Cu and
Au+Au systems shows an interesting scaling of the cluster size with the
measured fraction of total cross section (which is related to $b/2R$),
suggesting a geometric origin. These results should provide insight into the
hadronization stage of the hot and dense medium created in heavy ion
collisions.Comment: 4 pages, 5 figures, presented at the 19th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur,
India, February 4-10, 200

### Two point extremal Gromov-Witten invariants of Hilbert schemes of points on surfaces

Given an algebraic surface $X$, the Hilbert scheme $X^{[n]}$ of $n$-points on
$X$ admits a contraction morphism to the $n$-fold symmetric product $X^{(n)}$
with the extremal ray generated by a class $\beta_n$ of a rational curve. We
determine the two point extremal GW-invariants of $X^{[n]}$ with respect to the
class $d\beta_n$ for a simply-connected projective surface $X$ and the quantum
first Chern class operator of the tautological bundle on $X^{[n]}$. The methods
used are vertex algebraic description of $H^*(X^{[n]})$, the localization
technique applied to $X=\mathbb P^2$, and a generalization of the reduction
theorem of Kiem-J. Li to the case of meromorphic 2-forms

### Comment on "Cosmological Topological Massive Gravitons and Photons"

In a recent paper (arXiv: 0801.4566) it was shown that all global energy
eigenstates of asymptotically $AdS_3$ chiral gravity have non-negative energy
at the linearized level. This result was questioned (arXiv: 0803.3998) by
Carlip, Deser, Waldron and Wise (CDWW), who work on the Poincare patch. They
exhibit a linearized solution of chiral gravity and claim that it has negative
energy and is smooth at the boundary. We show that the solution of CDWW is
smooth only on that part of the boundary of $AdS_3$ included in the Poincare
patch. Extended to global $AdS_3$, it is divergent at the boundary point not
included in the Poincare patch. Hence it is consistent with the results of
(arXiv: 0801.4566).Comment: 4 pages, comment on arXiv 0803.3998 [hep-th

### Quantum differential cryptanalysis to the block ciphers

Differential cryptanalysis is one of the most popular methods in attacking
block ciphers. However, there still some limitations in traditional
differential cryptanalysis. On the other hand, researches of quantum algorithms
have made great progress nowadays. This paper proposes two methods to apply
quantum algorithms in differential cryptanalysis, and analysis their
efficiencies and success probabilities. One method is using quantum algorithm
in the high probability differential finding period for every S-Box. The second
method is taking the encryption as a whole, using quantum algorithm in this
process.Comment: 11 pages, no figure

### Synchronized output regulation of nonlinear multi-agent systems

This paper considers the synchronized output regulation (SOR) problem of
nonlinear multi-agent systems with switching graph. The SOR means that all
agents regulate their outputs to synchronize on the output of a predefined
common exosystem. Each agent constructs its local exosystem with the same
dynamics as that of the common exosystem and exchanges the state information of
the local exosystem. It is shown that the SOR is solvable under the assumptions
same as that for nonlinear output regulation of a single agent, if the
switching graph satisfies the bounded interconnectivity times condition. Both
state feedback and output feedback are addressed. A numerical simulation is
made to show the efficacy of the analytic results.Comment: 20 pages, 2 figures, submitted to International Journal of Contro

### Contragredient representations over local fields of positive characteristic

It is conjectured by Adams-Vogan and Prasad that under the local Langlands
correspondence, the L-parameter of the contragredient representation equals
that of the original representation composed with the Chevalley involution of
the L-group. We verify a variant of their prediction for all connected
reductive groups over local fields of positive characteristic, in terms of the
local Langlands parameterization of Genestier-Lafforgue. We deduce this from a
global result for cuspidal automorphic representations over function fields,
which is in turn based on a description of the transposes of V. Lafforgue's
excursion operators.Comment: 42 pages. Updated the reference

### Dynamical transitions in a modulated Landau-Zener model with finite driving fields

We investigate a special time-dependent quantum model which assumes the
Landau-Zener driving form but with an overall modulation of the intensity of
the pulsing field. We demonstrate that the dynamics of the system, including
the two-level case as well as its multi-level extension, is exactly solvable
analytically. Differing from the original Landau-Zener model, the nonadiabatic
effect of the evolution in the present driving process does not destroy the
desired population transfer. As the sweep protocol employs only the finite
driving fields which tend to zero asymptotically, the cutoff error due to the
truncation of the driving pulse to the finite time interval turns out to be
negligibly small. Furthermore, we investigate the noise effect on the driving
protocol due to the dissipation of the surrounding environment. The losses of
the fidelity in the protocol caused by both the phase damping process and the
random spin flip noise are estimated by solving numerically the corresponding
master equations within the Markovian regime.Comment: 6 pages, 4 figure

- β¦