841 research outputs found
A Renormalization Group For Treating 2D Coupled Arrays of Continuum 1D Systems
We study the spectrum of two dimensional coupled arrays of continuum
one-dimensional systems by wedding a density matrix renormalization group
procedure to a renormalization group improved truncated spectrum approach. To
illustrate the approach we study the spectrum of large arrays of coupled
quantum Ising chains. We demonstrate explicitly that the method can treat the
various regimes of chains, in particular the three dimensional Ising ordering
transition the chains undergo as a function of interchain coupling.Comment: 5 pages, 4 figure
A Numerical Renormalization Group for Continuum One-Dimensional Systems
We present a renormalization group (RG) procedure which works naturally on a
wide class of interacting one-dimension models based on perturbed (possibly
strongly) continuum conformal and integrable models. This procedure integrates
Kenneth Wilson's numerical renormalization group with Al. B. Zamolodchikov's
truncated conformal spectrum approach. Key to the method is that such theories
provide a set of completely understood eigenstates for which matrix elements
can be exactly computed. In this procedure the RG flow of physical observables
can be studied both numerically and analytically. To demonstrate the approach,
we study the spectrum of a pair of coupled quantum Ising chains and correlation
functions in a single quantum Ising chain in the presence of a magnetic field.Comment: 4 pages, 4 figure
Human Capital Investments Among Veterinarians
Professional labor markets can be affected by alternating periods of excess or scarcity in labor. The phenomenon is most prevalent in labor markets where a substantial lag occurs between occupational choice and labor market entry. In this paper, a unique longitudinal dataset from veterinary labor markets is used to identify factors significantly associated with volatility in labor supply. Our econometric analysis establishes a statistically significant relationship between boom-bust cycles in labor and certain pertinent variables: entry-level earnings, a demand proxy, and supply-side features. Results support the notion that decision-makers gauge the expected levels of these variables when making career choices
Statistics of Heat Transfer in Mesoscopic Circuits
A method to calculate the statistics of energy exchange between quantum
systems is presented. The generating function of this statistics is expressed
through a Keldysh path integral. The method is first applied to the problem of
heat dissipation from a biased mesoscopic conductor into the adjacent
reservoirs. We then consider energy dissipation in an electrical circuit around
a mesoscopic conductor. We derive the conditions under which measurements of
the fluctuations of heat dissipation can be used to investigate higher order
cumulants of the charge counting statistics of a mesoscopic conductor.Comment: 9 pages, 6 figure
Continuous Neel to Bloch Transition as Thickness Increases: Statics and Dynamics
We analyze the properties of Neel and Bloch domain walls as a function of
film thickness h, for systems where, in addition to exchange, the dipole-dipole
interaction must be included. The Neel to Bloch phase transition is found to be
a second order transition at hc, mediated by a single unstable mode that
corresponds to oscillatory motion of the domain wall center. A uniform
out-of-plane rf-field couples strongly to this critical mode only in the Neel
phase. An analytical Landau theory shows that the critical mode frequency
varies as the square root of (hc - h) just below the transition, as found
numerically.Comment: 4 pages, 4 figure
Analytical and micromagnetic study of a Neel domain wall
Journals published by the American Physical Society can be found at http://journals.aps.org/For ferromagnets with exchange, dipolar interaction, and uniaxial anisotropy, by both analytic methods and micromagnetic simulations we study Neel domain walls in thin ferromagnetic strips of finite width. Comparison of the numerical results with the analytics yields parameter values that had been unspecified by the analytics, and determines the modifications needed to describe the magnetization both near the strip center and near the boundaries. With no uniaxial anisotropy, the domain wall center can be described by the same hyperbolic secant form as with uniaxial anisotropy, but the effective anisotropy constant must now be thought of as increasing with increasing film thickness and decreasing with increasing film width
Interaction effects on magnetooscillations in a two-dimensional electron gas
Motivated by recent experiments, we study the interaction corrections to the
damping of magnetooscillations in a two-dimensional electron gas (2DEG). We
identify leading contributions to the interaction-induced damping which are
induced by corrections to the effective mass and quantum scattering time. The
damping factor is calculated for Coulomb and short-range interaction in the
whole range of temperatures, from the ballistic to the diffusive regime. It is
shown that the dominant effect is that of the renormalization of the effective
electron mass due to the interplay of the interaction and impurity scattering.
The results are relevant to the analysis of experiments on magnetooscillations
(in particular, for extracting the value of the effective mass) and are
expected to be useful for understanding the physics of a high-mobility 2DEG
near the apparent metal-insulator transition.Comment: 24 pages; subsection adde
Comment on "Critique of the foundations of time-dependent density functional theory" [Phys. Rev.A. 75, 022513 (2007)]
A recent paper (Phys. Rev A. 75, 022513 (2007), arXiv:cond-mat/0602020)
challenges exact time-dependent density functional theory (TDDFT) on several
grounds. We explain why these criticisms are either irrelevant or incorrect,
and that TDDFT is both formally exact and predictive.Comment: 4 pages; This is a Comment on the paper cited above, also at
arXiv:cond-mat/060202
Homologous Seminal Plasma and Glutathione Promote Pre-capacitation Motility and Structural Stability of Cryopreserved Ram Spermatozoa
Reduced glutathione (GSH) and homologous ram seminal plasma (HSP), used as additives in cryopreserving (CP) media prior to freezing, showed conflicting results in retaining structural integrity and progressive motility in post-thawed ram spermatozoa. The aims of this research were (1) to assess the effect of GSH and/or HSP supplementation via soybean-lecithin CP extender on cryopreserved ram spermatozoa viability, morphology and motility pattern; and (2) to assess the effect of incubation in the context of the previous aim. Quantitatively and qualitatively, homogenized and pooled ram ejaculates (N=10) were extended with one of the following extenders Control (C)-tris-based, GSH and HSP-free, experimental-1 (E1)-C + GSH 5 mM, experimental-2 (E2)-C + HSP 20 % and experimental-3 (E3)-GSH 5 mM + HSP 20 %. Following thawing, samples were taken at 0-A nd 3-hours from each group (n=10) and were assessed for spermatozoa viability, morphology, and motility pattern. C-0h samples yielded a spermatozoa population with low viability, altered head morphology and highly deviated motility pattern. E3-3h samples yielded spermatozoa with unaffected viability, head morphology and high progressive motility. In conclusion, E3 extender added to cryopreserved-thawed ram spermatozoa is most efficient in obtaining high viability, unaltered head morphology, and progressive motility
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