55,351 research outputs found
Z -> b\bar{b} Versus Dynamical Electroweak Symmetry Breaking involving the Top Quark
In models of dynamical electroweak symmetry breaking which sensitively
involve the third generation, such as top quark condensation, the effects of
the new dynamics can show up experimentally in Z->b\bar{b}. We compare the
sensitivity of Z->b\bar{b} and top quark production at the Tevatron to models
of the new physics. Z->b\bar{b} is a relatively more sensitive probe to new
strongly coupled U(1) gauge bosons, while it is generally less sensitive a
probe to new physics involving color octet gauge bosons as is top quark
production itself. Nonetheless, to accomodate a significant excess in
Z->b\bar{b} requires choosing model parameters that may be ruled out within run
I(b) at the Tevatron.Comment: LaTex file, 19 pages + 2 Figs., Fermilab-Pub-94/231-
Evidence for the existence of nonradial solar oscillations: Solar rotation
The coherent properties of six oscillations over a two week period in which seven days of equatorial diameter measurements were analyzed, are confirmed by the addition of an extra day of data. The two large 1 (the principal order number in the spherical harmonic expansion of the eigenfunction) g-mode oscillations may be candidates for the slowly rotating mode locked structures. For the four low frequency p-modes, periodic nature is observed in the daily power levels, varying with periods of several days. This is attributed to beating between rotationally split m states for a given 1 value. Nonradial modes are a major contribution to the observed solar oscillations. The nonradial character of the observed modes allows the depth dependence of the internal solar rotation to be investigated
Dynamics of Domain Walls for Split and Runaway Potentials
We demonstrate that the evolution of wall-like inhomogeneities in run-away
potentials, characteristic of dynamical supersymmetry breaking and moduli
stabilisation, is very similar to the evolution of domain wall networks
associated with double well potentials. Instabilities that would lead to a
rapid decay of domain walls can be significantly ameliorated by compensation
effects between a non-degeneracy of the vacua and a biased initial
distribution, which can be naturally expected in a wide class or particle
physics models that lead to out-of-equilibrium phase transitions. Within this
framework, it is possible to obtain domain walls that live long enough to be
relevant for the cosmic power spectrum and galaxy clustering, while being
compatible with the observed cosmic microwave background anisotropies.Comment: 30 pages, 9 figure
An exact formalism to study the thermodynamic properties of hard-sphere systems under spherical confinement
This paper presents a modified grand canonical ensemble which provides a new
simple and efficient scheme to study few-body fluid-like inhomogeneous systems
under confinement. The new formalism is implemented to investigate the exact
thermodynamic properties of a hard sphere (HS) fluid-like system with up to
three particles confined in a spherical cavity. In addition, the partition
function of this system was used to analyze the surface thermodynamic
properties of the many-HS system and to derive the exact curvature dependence
of both the surface tension and adsorption in powers of the density. The
expressions for the surface tension and the adsorption were also obtained for
the many- HS system outside of a fixed hard spherical object. We used these
results to derive the dependence of the fluid-substrate Tolman length up to
first order in density.Comment: 6 figures. The paper includes new exact results about hard spheres
fluid-like system
Search for Narrow-Width ttbar Resonances in ppbar Collisions at center of mass energy = 1.8 TeV
We present a preliminary result on a search for narrow-width resonances that
decay into ttbar pairs using 130 pb^{-1} of lepton plus jets data in ppbar
collisions at center of mass energy = 1.8 TeV. No significant deviation from
Standard Model prediction is observed. 95% C.L. upper limits on the production
cross section of the narrow-width resonance times its branching fraction to
ttbar are presented for different resonance masses, M_X. We also exclude the
existence of a leptophobic topcolor particle, X, with M_X < 560 GeV/c^2 for a
width \Gamma_X = 0.012 M_X.Comment: 3 pages, 1 figure; Submitted for proceedings of 5th International
Conference on Quark Confinement and Hadron spectrum, held in Italy, from
11-14 Sep., 200
Fluids confined in wedges and by edges: Virial series for the line-thermodynamic properties of hard spheres
This work is devoted to analyze the relation between the thermodynamic properties of a confined fluid and the shape of its confining vessel. Recently, new insights in this topic were found through the study of cluster integrals for inhomogeneous fluids that revealed the dependence on the vessel shape of the low density behavior of the system. Here, the statistical mechanics and thermodynamics of fluids confined in wedges or by edges is revisited, focusing on their cluster integrals. In particular, the well known hard sphere fluid, which was not studied in this framework so far, is analyzed under confinement and its thermodynamic properties are analytically studied up to order two in the density. Furthermore, the analysis is extended to the confinement produced by a corrugated wall. These results rely on the obtained analytic expression for the second cluster integral of the confined hard sphere system as a function of the opening dihedral angle 0 < β < 2Ï€. It enables a unified approach to both wedges and edges.Fil: Urrutia, Ignacio. Comisión Nacional de EnergÃa Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentin
Two hard spheres in a pore: Exact Statistical Mechanics for different shaped cavities
The Partition function of two Hard Spheres in a Hard Wall Pore is studied
appealing to a graph representation. The exact evaluation of the canonical
partition function, and the one-body distribution function, in three different
shaped pores are achieved. The analyzed simple geometries are the cuboidal,
cylindrical and ellipsoidal cavities. Results have been compared with two
previously studied geometries, the spherical pore and the spherical pore with a
hard core. The search of common features in the analytic structure of the
partition functions in terms of their length parameters and their volumes,
surface area, edges length and curvatures is addressed too. A general framework
for the exact thermodynamic analysis of systems with few and many particles in
terms of a set of thermodynamic measures is discussed. We found that an exact
thermodynamic description is feasible based in the adoption of an adequate set
of measures and the search of the free energy dependence on the adopted measure
set. A relation similar to the Laplace equation for the fluid-vapor interface
is obtained which express the equilibrium between magnitudes that in extended
systems are intensive variables. This exact description is applied to study the
thermodynamic behavior of the two Hard Spheres in a Hard Wall Pore for the
analyzed different geometries. We obtain analytically the external work, the
pressure on the wall, the pressure in the homogeneous zone, the wall-fluid
surface tension, the line tension and other similar properties
Sclera solar diameter observations
Focus is given to possible variations in solar luminosity and accurate methods of monitoring it. Aside from direct bolometry, one methodology for this type of research makes use of measurements of the solar diameter and limb darkening function as indirect indicators of the solar luminosity. This approach was reviewed
Three-body interactions in complex fluids: virial coefficients from simulation finite-size effects
A simulation technique is described for quantifying the contribution of
three-body interactions to the thermodynamical properties of coarse-grained
representations of complex fluids. The method is based on comparing the third
virial coefficient for a complex fluid with that of an approximate
coarse-grained model described by a pair potential. To obtain we
introduce a new technique which expresses its value in terms of the measured
volume-dependent asymptote of a certain structural function. The strategy is
applicable to both Molecular Dynamics and Monte Carlo simulation. Its utility
is illustrated via measurements of three-body effects in models of star polymer
and highly size-asymmetrical colloid-polymer mixtures.Comment: 13 pages, 8 figure
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