7,292 research outputs found
CPA for charge ordering in the extended Hubbard model
We study charge ordering in the extended Hubbard model with both on-site and
nearest neighbor Coulomb repulsion (U and V, respectively) within the Coherent
potential approximation (CPA). The phase boundary between the homogeneous and
charge ordered phase for the square lattice is obtained for different values of
U. It is shown that at quarter filling for all values of U the charge ordering
exists only if the inter-site Coulomb repulsion V exceeds certain critical
value which is of the order of the kinetic energy t. At finite temperature a
reentrant transition is found in some region of V.Comment: 5 pages, 4 figure
Spinning Dust Emission: Effects of irregular grain shape, transient heating and comparison with WMAP results
Planck is expected to answer crucial questions on the early Universe, but it
also provides further understanding on anomalous microwave emission. Electric
dipole emission from spinning dust grains continues to be the favored
interpretation of anomalous microwave emission. In this paper, we present a
method to calculate the rotational emission from small grains of irregular
shape with moments of inertia . We show that a torque-free
rotating irregular grain with a given angular momentum radiates at multiple
frequency modes. The resulting spinning dust spectrum has peak frequency and
emissivity increasing with the degree of grain shape irregularity, which is
defined by . We discuss how the orientation of dipole moment
\bmu in body coordinates affects the spinning dust spectrum for different
regimes of internal thermal fluctuations. We show that the spinning dust
emissivity for the case of strong thermal fluctuations is less sensitive to the
orientation of \bmu than in the case of weak thermal fluctuations. We
calculate spinning dust spectra for a range of gas density and dipole moment.
The effect of compressible turbulence on spinning dust emission intensity is
investigated. We show that the emission intensity in a turbulent medium
increases by a factor from 1.2-1.4 relative to that in a uniform medium, as
sonic Mach number increases from 2-7. Finally, spinning dust parameters
are constrained by fitting our improved model to five-year {\it Wilkinson
Microwave Anisotropy Probe} cross-correlation foreground spectra, for both the
H-correlated and 100 m-correlated emission spectra.Comment: 24 pages, 17 figures, relation to molecular rotation spectra added,
accepted by Astrophysical Journa
Ultrasoft NLL Running of the Nonrelativistic O(v) QCD Quark Potential
Using the nonrelativistic effective field theory vNRQCD, we determine the
contribution to the next-to-leading logarithmic (NLL) running of the effective
quark-antiquark potential at order v (1/mk) from diagrams with one potential
and two ultrasoft loops, v being the velocity of the quarks in the c.m. frame.
The results are numerically important and complete the description of ultrasoft
next-to-next-to-leading logarithmic (NNLL) order effects in heavy quark pair
production and annihilation close to threshold.Comment: 25 pages, 7 figures, 3 tables; minor modifications, typos corrected,
references added, footnote adde
A Renormalization Group Improved Calculation of Top Quark Production near Threshold
The top quark cross section close to threshold in annihilation is
computed including the summation of logarithms of the velocity at
next-to-next-to-leading-logarithmic order in QCD. The remaining theoretical
uncertainty in the normalization of the total cross section is at the few
percent level, an order of magnitude smaller than in previous
next-to-next-to-leading order calculations. This uncertainty is smaller than
the effects of a light standard model Higgs boson.Comment: changed figures, added reference
Androgen receptor-dependent and -independent mechanisms driving prostate cancer progression: Opportunities for therapeutic targeting from multiple angles.
Despite aggressive treatment for localized cancer, prostate cancer (PC) remains a leading cause of cancer-related death for American men due to a subset of patients progressing to lethal and incurable metastatic castrate-resistant prostate cancer (CRPC). Organ-confined PC is treated by surgery or radiation with or without androgen deprivation therapy (ADT), while options for locally advanced and disseminated PC include radiation combined with ADT, or systemic treatments including chemotherapy. Progression to CRPC results from failure of ADT, which targets the androgen receptor (AR) signaling axis and inhibits AR-driven proliferation and survival pathways. The exact mechanisms underlying the transition from androgen-dependent PC to CRPC remain incompletely understood. Reactivation of AR has been shown to occur in CRPC despite depletion of circulating androgens by ADT. At the same time, the presence of AR-negative cell populations in CRPC has also been identified. While AR signaling has been proposed as the primary driver of CRPC, AR-independent signaling pathways may represent additional mechanisms underlying CRPC progression. Identification of new therapeutic strategies to target both AR-positive and AR-negative PC cell populations and, thereby, AR-driven as well as non-AR-driven PC cell growth and survival mechanisms would provide a two-pronged approach to eliminate CRPC cells with potential for synthetic lethality. In this review, we provide an overview of AR-dependent and AR-independent molecular mechanisms which drive CRPC, with special emphasis on the role of the Jak2-Stat5a/b signaling pathway in promoting castrate-resistant growth of PC through both AR-dependent and AR-independent mechanisms
Spin Resistivity in the Frustrated Model
We study in this paper the resistivity encountered by Ising itinerant spins
traveling in the so-called frustrated simple cubic Ising lattice. For
the lattice, we take into account the interactions between nearest-neighbors
and next-nearest-neighbors, and respectively. Itinerant spins
interact with lattice spins via a distance-dependent interaction. We also take
into account an interaction between itinerant spins. The lattice is frustrated
in a range of in which we show that it undergoes a very strong
first-order transition. Using Monte Carlo simulation, we calculate the
resistivity of the itinerant spins and show that the first-order
transition of the lattice causes a discontinuity of .Comment: submitted for publicatio
Renormalization group-like proof of the universality of the Tutte polynomial for matroids
In this paper we give a new proof of the universality of the Tutte polynomial
for matroids. This proof uses appropriate characters of Hopf algebra of
matroids, algebra introduced by Schmitt (1994). We show that these Hopf algebra
characters are solutions of some differential equations which are of the same
type as the differential equations used to describe the renormalization group
flow in quantum field theory. This approach allows us to also prove, in a
different way, a matroid Tutte polynomial convolution formula published by
Kook, Reiner and Stanton (1999). This FPSAC contribution is an extended
abstract.Comment: 12 pages, 3 figures, conference proceedings, 25th International
Conference on Formal Power Series and Algebraic Combinatorics, Paris, France,
June 201
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