18,001 research outputs found
Supersymmetric Extension of the Quantum Spherical Model
In this work, we present a supersymmetric extension of the quantum spherical
model, both in components and also in the superspace formalisms. We find the
solution for short/long range interactions through the imaginary time formalism
path integral approach. The existence of critical points (classical and
quantum) is analyzed and the corresponding critical dimensions are determined.Comment: 21 pages, fixed notation to match published versio
T-Duality in 2-D Integrable Models
The non-conformal analog of abelian T-duality transformations relating pairs
of axial and vector integrable models from the non abelian affine Toda family
is constructed and studied in detail.Comment: 14 pages, Latex, v.2 misprints corrected, reference added, to appear
in J. Phys.
Discrete Time Evolution and Energy Nonconservation in Noncommutative Physics
Time-space noncommutativity leads to quantisation of time and energy
nonconservation when time is conjugate to a compact spatial direction like a
circle. In this context energy is conserved only modulo some fixed unit. Such a
possibility arises for example in theories with a compact extra dimension with
which time does not commute. The above results suggest striking
phenomenological consequences in extra dimensional theories and elsewhere. In
this paper we develop scattering theory for discrete time translations. It
enables the calculation of transition probabilities for energy nonconserving
processes and has a central role both in formal theory and phenomenology.
We can also consider space-space noncommutativity where one of the spatial
directions is a circle. That leads to the quantisation of the remaining spatial
direction and conservation of momentum in that direction only modulo some fixed
unit, as a simple adaptation of the results in this paper shows.Comment: 17 pages, LaTex; minor correction
Effective models of quantum gravity induced by Planck scale modifications in the covariant quantum algebra
In this paper we introduce a modified covariant quantum algebra based in the
so-called Quesne-Tkachuk algebra. By means of a deformation procedure we arrive
at a class of higher derivative models of gravity. The study of the particle
spectra of these models reveals an equivalence with the physical content of the
well-known renormalizable and super-renormalizable higher derivative gravities.
The particle spectrum exhibits the presence of spurious complex ghosts and, in
light of this problem, we suggest an interesting interpretation in the context
of minimal length theories. Also, a discussion regarding the non-relativistic
potential energy is proposed.Comment: Small corrections were made; improved figures; results unchanged;
published versio
Structural properties of crumpled cream layers
The cream layer is a complex heterogeneous material of biological origin
which forms spontaneously at the air-milk interface. Here, it is studied the
crumpling of a single cream layer packing under its own weight at room
temperature in three-dimensional space. The structure obtained in these
circumstances has low volume fraction and anomalous fractal dimensions. Direct
means and noninvasive NMR imaging technique are used to investigate the
internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy
Phase Diagram of the Attractive Hubbard Model with Inhomogeneous Interactions
The phase diagram of the attractive Hubbard model with spatially
inhomogeneous interactions is obtained using a single site dynamical mean field
theory like approach. The model is characterized by three parameters: the
interaction strength, the active fraction (fraction of sites with the
attractive interaction), and electron filling. The calculations indicate that
in a parameter regime with intermediate values of interaction strength
(compared to the bare bandwidth of the electrons), and intermediate values of
the active fraction, "non-BCS" superconductivity is obtained. The results of
this work are likely to be relevant to many systems with spatially
inhomogeneous superconductivity such as strongly correlated oxides, systems
with negative U centers, and, in future, cold atom optical lattices.Comment: 9 pages, 7 figures, to appear in Physical Review
Fate of conjugated natural and synthetic steroid estrogens in crude sewage and activated sludge batch studies
This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Environmental Science & Technology, copyright © American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/es801952h.Steroids are excreted from the human body in the conjugated form but are present in sewage influent and effluent as the free steroid, the major source of estrogenic activity observed in water courses. The fate of sulfate and glucuronide conjugated steroid estrogens was investigated in batch studies using activated sludge grown on synthetic sewage in a laboratory-scale Husmann simulation and crude sewage from the field. A clear distinction between the fate of sulfate and glucuronide conjugates was observed in both matrices, with sulfated conjugates proving more recalcitrant and glucuronide deconjugation preferential in crude sewage. For each conjugate, the free steroid was observed in the biotic samples. The degree of free steroid formation was dependent on the conjugate moiety, favoring the glucuronide. Subsequent degradation of the free steroid (and sorption to the activated sludge solid phase) was evaluated. Deconjugation followed the first order reaction rate with rate constants for 17α-ethinylestradiol 3-glucuronide, estriol 16α-glucuronide, and estrone 3-glucuronide determined as 0.32, 0.24, and 0.35 h respectively. The activated sludge solid retention time over the range of 3−9 days had 74 to 94% of sulfate conjugates remaining after 8 h. In contrast, a correlation between increasing temperature and decreasing 17α-ethinylestradiol 3-glucuronide concentrations in the activated sludge observed no conjugate present in the AS following 8 h at 22 °C Based on these batch studies and literature excretion profiles, a hypothesis is presented on which steroids and what form (glucuronide, sulfate, or free) will likely enter the sewage treatment plant.EPSR
On the Nonabelian Aharonov Bohm Scattering of Spinless Particles
The Aharonov Bohm scattering for spinless, isospin 1/2, particles interacting
through a nonabelian Chern-Simons field is studied. Starting from the
relativistic quantum field theory and using a Coulomb gauge formulation, the
one loop renormalization program is implemented. Through the introduction of an
intermediary cutoff, separating the regions of high and low integration
momentum, the nonrelativistic limit is derived. The next to leading
relativistic approximation is also determined. In this approach quantum field
theory vacuum polarization effects are automatically incorporated.Comment: 20 pages, 8 figures, revtex. Misspelled reference corrected and new
references adde
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