29,703 research outputs found
Computing Early-time Dynamics in Heavy Ion Collisions: Status, Problems and Prospects
We discuss some recent developments towards a quantitative understanding of
the production and early-time evolution of bulk quark-gluon matter in
ultrarelativistic heavy ion collisions.Comment: 10 pages, Invited Talk, Workshop on "QCD evolution of parton
distributions: from collinear to non-collinear case", Newport News, VA, 8 - 9
Apr 201
Summer Workshop on Near-Earth Resources
The possible large scale use of extraterrestrial resources was addressed, either to construct structures in space or to return to Earth as supplements for terrestrial resources. To that end, various specific recommendations were made by the participants in the summer study on near-Earth resources, held at La Jolla, California, 6 to 13 August, 1977. The Moon and Earth-approaching asteroids were considered. Summaries are included of what is known about their compositions and what needs to be learned, along with recommendations for missions designed to provide the needed data. Tentative schedules for these projects are also offered
Electron transfer through a multiterminal quantum ring: magnetic forces and elastic scattering effects
We study electron transport through a semiconductor quantum ring with one
input and two output terminals for an elastic scatterer present within one of
the arms of the ring. We demonstrate that the scatterer not only introduces
asymmetry in the transport probability to the two output leads but also reduces
the visibility of the Aharonov-Bohm conductance oscillations. This reduction
occurs in spite of the phase coherence of the elastic scattering and is due to
interruption of the electron circulation around the ring by the potential
defect. The results are in a qualitative agreement with a recent experiment by
Strambini et al. [Phys. Rev. B {\bf 79}, 195443 (2009)]. We also indicate that
the magnetic symmetry of the sum of conductance of both the output leads as
obtained in the experiment can be understood as resulting from the invariance
of backscattering to the input lead with respect to the magnetic field
orientation.Comment: submitted to PR
Hodograph solutions of the dispersionless coupled KdV hierarchies, critical points and the Euler-Poisson-Darboux equation
It is shown that the hodograph solutions of the dispersionless coupled KdV
(dcKdV) hierarchies describe critical and degenerate critical points of a
scalar function which obeys the Euler-Poisson-Darboux equation. Singular
sectors of each dcKdV hierarchy are found to be described by solutions of
higher genus dcKdV hierarchies. Concrete solutions exhibiting shock type
singularities are presented.Comment: 19 page
Angular EPR paradox
The violation of local uncertainty relations is a valuable tool for detecting
entanglement, especially in multi-dimensional systems. The orbital angular
momentum of light provides such a multi-dimensional system. We study quantum
correlations for the conjugate variables of orbital angular momentum and
angular position. We determine an experimentally testable criterion for the
demonstration of an angular version of the EPR paradox. For the interpretation
of future experimental results from our proposed setup, we include a model for
the indeterminacies inherent to the angular position measurement. For this
measurement angular apertures are used to determine the probability density of
the angle. We show that for a class of aperture functions a demonstration of an
angular EPR paradox, according to our criterion, is to be expected.Comment: 21 pages, 9 figures, to be published in J. Mod. Opt. special issue on
quantum imagin
Scalar Representations and Minimal Flavor Violation
We discuss the representations that new scalar degrees of freedom (beyond
those in the minimal standard model) can have if they couple to quarks in a way
that is consistent with minimal flavor violation. If the new scalars are
singlets under the flavor group then they must be color singlets or color
octets. In this paper we discuss the allowed representations and renormalizable
couplings when the new scalars also transform under the flavor group. We find
that color \bar{3} and 6 representations are also allowed. We focus on the
cases where the new scalars can have renormalizable Yukawa couplings to the
quarks without factors of the quark Yukawa matrices. The renormalizable
couplings in the models we introduce automatically conserve baryon number.Comment: 18 pages, 2 figures V2: Lepton MFV protection of baryon number
discusse
Uranium(III) coordination chemistry and oxidation in a flexible small-cavity macrocycle
U(III) complexes of the conformationally flexible, small-cavity macrocycle trans-calix[2]benzene[2]pyrrolide (L)2–, [U(L)X] (X = O-2,6-tBu2C6H3, N(SiMe3)2), have been synthesized from [U(L)BH4] and structurally characterized. These complexes show binding of the U(III) center in the bis(arene) pocket of the macrocycle, which flexes to accommodate the increase in the steric bulk of X, resulting in long U–X bonds to the ancillary ligands. Oxidation to the cationic U(IV) complex [U(L)X][B(C6F5)4] (X = BH4) results in ligand rearrangement to bind the smaller, harder cation in the bis(pyrrolide) pocket, in a conformation that has not been previously observed for (L)2–, with X located between the two ligand arene rings
Effective Kinetic Theory for High Temperature Gauge Theories
Quasiparticle dynamics in relativistic plasmas associated with hot,
weakly-coupled gauge theories (such as QCD at asymptotically high temperature
) can be described by an effective kinetic theory, valid on sufficiently
large time and distance scales. The appropriate Boltzmann equations depend on
effective scattering rates for various types of collisions that can occur in
the plasma. The resulting effective kinetic theory may be used to evaluate
observables which are dominantly sensitive to the dynamics of typical
ultrarelativistic excitations. This includes transport coefficients
(viscosities and diffusion constants) and energy loss rates. We show how to
formulate effective Boltzmann equations which will be adequate to compute such
observables to leading order in the running coupling of high-temperature
gauge theories [and all orders in ]. As previously proposed
in the literature, a leading-order treatment requires including both
particle scattering processes as well as effective ``'' collinear
splitting processes in the Boltzmann equations. The latter account for nearly
collinear bremsstrahlung and pair production/annihilation processes which take
place in the presence of fluctuations in the background gauge field. Our
effective kinetic theory is applicable not only to near-equilibrium systems
(relevant for the calculation of transport coefficients), but also to highly
non-equilibrium situations, provided some simple conditions on distribution
functions are satisfied.Comment: 40 pages, new subsection on soft gauge field instabilities adde
Integrability of one degree of freedom symplectic maps with polar singularities
In this paper, we treat symplectic difference equations with one degree of
freedom. For such cases, we resolve the relation between that the dynamics on
the two dimensional phase space is reduced to on one dimensional level sets by
a conserved quantity and that the dynamics is integrable, under some
assumptions. The process which we introduce is related to interval exchange
transformations.Comment: 10 pages, 2 figure
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