1,683 research outputs found
One-loop QCD interconnection effects in pair production of top quarks
We calculate the one-loop non-factorizable QCD corrections to the production
and decay of pairs of top quarks at various collider experiments. These
non-factorizable corrections interconnect the different production and decay
stages of the off-shell top-pair production processes. This in particular
affects the invariant-mass distributions of the off-shell top quarks, resulting
in a shift of the maximum of the distorted Breit-Wigner distributions. Although
the non-factorizable corrections can be large, the actual shift in the mass as
determined from the peak position of the corrected Breit-Wigner line-shape is
below 100\MeV.Comment: 11 pages, LaTeX2e (uses axodraw.sty), 2 ps figures included; some
numerical results changed, reference adde
Инновационные методы в области управления персоналом
Целью статьи является обоснование инновационных методов в области управления персоналом
Density functional theory and demixing of binary hard rod-polymer mixtures
A density functional theory for a mixture of hard rods and polymers modeled
as chains built of hard tangent spheres is proposed by combining the functional
due to Yu and Wu for the polymer mixtures [J. Chem. Phys. {\bf 117}, 2368
(2002)] with the Schmidt's functional [Phys. Rev. E {\bf 63}, 50201 (2001)] for
rod-sphere mixtures. As a simple application of the functional, the demixing
transition into polymer-rich and rod-rich phases is examined. When the chain
length increases, the phase boundary broadens and the critical packing fraction
decreases. The shift of the critical point of a demixing transition is most
noticeable for short chains.Comment: 4 pages,2 figures, in press, PR
Low temperature electronic properties of Sr_2RuO_4 III: Magnetic fields
Based on the microscopic model introduced previously the observed specific
heat and ac-susceptibility data in the superconducting phase in Sr_2RuO_4 with
applied magnetic fields are described consistently within a phenomenological
approach. Discussed in detail are the temperature dependence of the upper
critical fields H_{c2} and H_2, the dependence of the upper critical fields on
the field direction, the linear specific heat below the superconducting phase
transition as a function of field or temperature, the anisotropy of the two
spatial components of the order parameter, and the fluctuation field H_p.Comment: 8 pages REVTEX, 4 figure
Capillary Condensation and Interface Structure of a Model Colloid-Polymer Mixture in a Porous Medium
We consider the Asakura-Oosawa model of hard sphere colloids and ideal
polymers in contact with a porous matrix modeled by immobilized configurations
of hard spheres. For this ternary mixture a fundamental measure density
functional theory is employed, where the matrix particles are quenched and the
colloids and polymers are annealed, i.e. allowed to equilibrate. We study
capillary condensation of the mixture in a tiny sample of matrix as well as
demixing and the fluid-fluid interface inside a bulk matrix. Density profiles
normal to the interface and surface tensions are calculated and compared to the
case without matrix. Two kinds of matrices are considered: (i) colloid-sized
matrix particles at low packing fractions and (ii) large matrix particles at
high packing fractions. These two cases show fundamentally different behavior
and should both be experimentally realizable. Furthermore, we argue that
capillary condensation of a colloidal suspension could be experimentally
accessible. We find that in case (ii), even at high packing fractions, the main
effect of the matrix is to exclude volume and, to high accuracy, the results
can be mapped onto those of the same system without matrix via a simple
rescaling.Comment: 12 pages, 9 figures, submitted to PR
Hydrogen-Helium Mixtures at High Pressure
The properties of hydrogen-helium mixtures at high pressure are crucial to
address important questions about the interior of Giant planets e.g. whether
Jupiter has a rocky core and did it emerge via core accretion? Using path
integral Monte Carlo simulations, we study the properties of these mixtures as
a function of temperature, density and composition. The equation of state is
calculated and compared to chemical models. We probe the accuracy of the ideal
mixing approximation commonly used in such models. Finally, we discuss the
structure of the liquid in terms of pair correlation functions.Comment: Proceedings article of the 5th Conference on Cryocrystals and Quantum
Crystals in Wroclaw, Poland, submitted to J. Low. Temp. Phys. (2004
Macromolecular theory of solvation and structure in mixtures of colloids and polymers
The structural and thermodynamic properties of mixtures of colloidal spheres
and non-adsorbing polymer chains are studied within a novel general
two-component macromolecular liquid state approach applicable for all size
asymmetry ratios. The dilute limits, when one of the components is at infinite
dilution but the other concentrated, are presented and compared to field theory
and models which replace polymer coils with spheres. Whereas the derived
analytical results compare well, qualitatively and quantitatively, with
mean-field scaling laws where available, important differences from ``effective
sphere'' approaches are found for large polymer sizes or semi-dilute
concentrations.Comment: 23 pages, 10 figure
Transport of charged particles by adjusting rf voltage amplitudes
We propose a planar architecture for scalable quantum information processing
(QIP) that includes X-junctions through which particles can move without
micromotion. This is achieved by adjusting radio frequency (rf) amplitudes to
move an rf null along the legs of the junction. We provide a proof-of-principle
by transporting dust particles in three dimensions via adjustable rf potentials
in a 3D trap. For the proposed planar architecture, we use regularization
techniques to obtain amplitude settings that guarantee smooth transport through
the X-junction.Comment: 16 pages, 10 figure
Perturbative Computation of the Gluonic Effective Action via Polyaokov's World-Line Path Integral
The Polyakov world-line path integral describing the propagation of gluon
field quanta is constructed by employing the background gauge fixing method and
is subsequently applied to analytically compute the divergent terms of the one
(gluonic) loop effective action to fourth order in perturbation theory. The
merits of the proposed approach is that, to a given order, it reduces to
performing two integrations, one over a set of Grassmann and one over a set of
Feynman-type parameters through which one manages to accomodate all Feynman
diagrams entering the computation at once.Comment: 21 page
Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity
The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp
scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx}
orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized
description of the in-plane electron correlations the superconducting order
parameter is found to be a orbital-singlet spin-triplet with two spatial
components. The spatial anisotropy is 7%. The different components of the order
parameter give rise to two-dimensional gapless fluctuations. The phase
transition is of third order. The temperature dependence of the pair density,
specific heat, NQR, Knight shift, and susceptibility are in agreement with
experimental results.Comment: 20 pages REVTEX, 3 figure
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