849 research outputs found
BPS and non-BPS Domain Walls in Supersymmetric QCD with SU(3) Gauge Group
We study the spectrum of the domain walls interpolating between different
chirally asymmetric vacua in supersymmetric QCD with the SU(3) gauge group and
including 2 pairs of chiral matter multiplets in fundamental and
anti-fundamental representations. For small enough masses m < m* = .286... (in
the units of \Lambda), there are two different domain wall solutions which are
BPS-saturated and two types of ``wallsome sphalerons''. At m = m*, two BPS
branches join together and, in the interval m* < m < m** = 3.704..., BPS
equations have no solutions but there are solutions to the equations of motion
describing a non-BPS domain wall and a sphaleron. For m > m**, there are no
solutions whatsoever.Comment: 10 pages LaTeX, 5 postscript 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
SeaSoar data collected on RRS "Discovery" Cruise 198 (Sterna) across Drake Passage and in the Bellingshausen Sea
The Zero-Removing Property and Lagrange-Type Interpolation Series
The classical Kramer sampling theorem, which provides a method for obtaining orthogonal sampling formulas, can be formulated in a more general nonorthogonal setting. In this setting, a challenging problem is to characterize the situations when the obtained nonorthogonal sampling formulas can be expressed as Lagrange-type interpolation series. In this article a necessary and sufficient condition is given in terms of the zero removing property. Roughly speaking, this property concerns the stability of the sampled functions on removing a finite number of their zeros
Domain Walls Zoo in Supersymmetric QCD
Solving numerically the equations of motion for the effective lagrangian
describing supersymmetric QCD with the SU(2) gauge group, we find a menagerie
of complex domain wall solutions connecting different chirally asymmetric
vacua. Some of these solutions are BPS saturated walls; they exist when the
mass of the matter fields does not exceed some critical value m < m* <
4.67059... There are also sphaleron branches (saddle points of the ebergy
functional). In the range m* < m < m** \approx 4.83, one of these branches
becomes a local minimum (which is not a BPS saturated one). At m > m*, the
complex walls disappear altogether and only the walls connecting a chirally
asymmetric vacuum with the chirally symmetric one survive.Comment: 23 pages, LaTeX, 11 figure
Single photoeffect on helium-like ions in the non-relativistic region
We present a generalization of the pioneering results obtained for single
K-shell photoionization of H-like ions by M. Stobbe [Ann. Phys. 7 (1930) 661]
to the case of the helium isoelectronic sequence. The total cross section of
the process is calculated, taking into account the correlation corrections to
first order of the perturbation theory with respect to the electron-electron
interaction. Predictions are made for the entire non-relativistic energy
domain. The phenomenon of dynamical suppression of correlation effects in the
ionization cross section is discussed.Comment: to be published in Physics Letters
Can One-Run-Fixed-Arrhenius Kerogen Analysis Provide Comparable Organofacies Results to Detailed Palynological Analysis? A Case Study from a Prospective Mississippian Source Rock Reservoir (Bowland Shale, UK)
Organofacies analysis, a fundamental component within source rock appraisal based on the study of kerogen within a source rock, is typically produced from microscopy (palynological) and geochemical (kerogen kinetic) data, both of which are costly to acquire. One-Run-Fixed-Arrhenius (ORFA) kerogen kinetic analysis based on Rock–Eval pyrolysis offers a substantially cheaper kinetic dataset. Here, ORFA and palynological analyses are compared in organofacies characterization of a prospective Mississippian source rock reservoir (Bowland Shale, UK). Two-end-member organofacies were determined based on the abundance of the 56 kcal/mol activation energy peak derived from ORFA data: absence ( 15%) indicating ‘organofacies B’ containing the highest proportion of sporomorphs (Type II kerogen). A mud-dominated slope setting for the rock reservoir was also used to test the accuracy of organofacies analysis in determining depositional environment. Organofacies A found within lithofacies deposited from dilute waning density flows and hemipelagic suspension settling occurred between shelf edge, slope and basin. Organofacies B found within lithofacies deposited from dilute waning density flows, and low-strength cohesive debrites occurred only within the lower slope. This study demonstrates that ORFA kerogen kinetic analysis provides comparable net results to palynological analysis, enabling cheaper and faster organic characterization during initial source rock appraisal. However, caution must be exercised in drawing interpretations as to biological source(s), organic matter mixing and preservation state(s) without additional investigation using data from detailed palynological analysis
Scintillation and charge extraction from the tracks of energetic electrons in superfluid helium-4
An energetic electron passing through liquid helium causes ionization along
its track. The ionized electrons quickly recombine with the resulting positive
ions, which leads to the production of prompt scintillation light. By applying
appropriate electric fields, some of the ionized electrons can be separated
from their parent ions. The fraction of the ionized electrons extracted in a
given applied field depends on the separation distance between the electrons
and the ions. We report the determination of the mean electron-ion separation
distance for charge pairs produced along the tracks of beta particles in
superfluid helium at 1.5 K by studying the quenching of the scintillation light
under applied electric fields. Knowledge of this mean separation parameter will
aid in the design of particle detectors that use superfluid helium as a target
material.Comment: 10 pages, 8 figure
One-loop results for the quark-gluon vertex in arbitrary dimension
Results on the one-loop quark-gluon vertex with massive quarks are reviewed,
in an arbitrary covariant gauge and in arbitrary space-time dimension. We show
how it is possible to get on-shell results from the general off-shell
expressions. The corresponding Ward-Slavnov-Taylor identity is discussed.Comment: 6 pages, LaTeX, including 1 figure, uses epsfig, requires
espcrc2.sty, contribution to the Zeuthen Workshop "Loops and Legs in Gauge
Theories" (Bastei, Germany, April 2000
Effects of Electron-Electron and Electron-Phonon Interactions in Weakly Disordered Conductors and Heterostuctures
We investigate quantum corrections to the conductivity due to the
interference of electron-electron (electron-phonon) scattering and elastic
electron scattering in weakly disordered conductors. The electron-electron
interaction results in a negative -correction in a 3D conductor. In
a quasi-two-dimensional conductor, ( is the thickness, is
the Fermi velocity), with 3D electron spectrum this correction is linear in
temperature and differs from that for 2D electrons (G. Zala et. al., Phys.
Rev.B {\bf 64}, 214204 (2001)) by a numerical factor. In a
quasi-one-dimensional conductor, temperature-dependent correction is
proportional to . The electron interaction via exchange of virtual phonons
also gives -correction. The contribution of thermal phonons interacting
with electrons via the screened deformation potential results in -term and
via unscreened deformation potential results in -term. The interference
contributions dominate over pure electron-phonon scattering in a wide
temperature range, which extends with increasing disorder.Comment: 6 pages, 2figure
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