14,274 research outputs found
Couplings and spectra in modular inflation
We analyze how the spectrum of perturbations produced in a multi-component
modular inflation model proposed by Kadota and Stewart depends on couplings
between the two moduli. Although some simple direct couplings give essentially
the same results as the original model, , simple
indirect couplings produce a power law spectrum, ,
which can naturally be close to scale invariant.Comment: 11 pages, format changed, some corrections of formula
Chiral restoration at finite temperature with meson loop corrections
We investigate chiral-restoration patterns of QCD for N_{c}=3 and N_{f}=2 at
finite temperature (T) and zero quark-chemical potential beyond the chiral
limit, indicating the explicit chiral-symmetry breaking. To this end, we employ
the instanton-vacuum configuration for the flavor SU(2) sector and the
Harrington-Shepard caloron for modifying relevant instanton parameters as
functions of T. The meson-loop corrections (MLC), which correspond to 1/N_{c}
corrections, are also taken into account to reproduce appropriate m_{q}
dependences of chiral order parameters. We compute chiral condensate as a
function of T and/or m_{q}. From the numerical calculations, we observe that
MLC play an important role to have a correct universality-class behavior of
chiral-restoration patterns in this framework, depending on m_{q}: Second-order
phase transition in the chiral limit, m_{q}=0 and crossover for m_{q}>0.
Without MLC, all the restoration patterns are crossover, due to simple
saddle-point approximations. It turns out that T^{\chi}_{c}=159 MeV in the
chiral limit and T^{\chi}_{c}=(177,186,196) MeV for m_{q}=(5,10,15) MeV, using
the phenomenological choices for the instanton parameters at T=0.Comment: 12 pages, 6 figure
Implementation of a Quantum Search Algorithm on a Nuclear Magnetic Resonance Quantum Computer
We demonstrate an implementation of a quantum search algorithm on a two qubit
NMR quantum computer based on cytosine.Comment: Six pages, three figure
Superconducting transition of a two-dimensional Josephson junction array in weak magnetic fields
The superconducting transition of a two-dimensional (2D) Josephson junction
array exposed to weak magnetic fields has been studied experimentally.
Resistance measurements reveal a superconducting-resistive phase boundary in
serious disagreement with the theoretical and numerical expectations. Critical
scaling analyses of the characteristics indicate contrary to the
expectations that the superconducting-to-resistive transition in weak magnetic
fields is associated with a melting transition of magnetic-field-induced
vortices directly from a pinned-solid phase to a liquid phase. The expected
depinning transition of vortices from a pinned-solid phase to an intermediate
floating-solid phase was not observed. We discuss effects of the
disorder-induced random pinning potential on phase transitions of vortices in a
2D Josephson junction array.Comment: 9 pages, 7 figures (EPS+JPG format), RevTeX
Forest Carbon Sequestration under the U.S. Biofuel Energy Policies
This paper analyzes impacts of the U.S. biofuel energy policies on the carbon sequestration by forest products, which is expressed as Harvested Wood Products (HWP) Contribution under the United Nations Framework Convention on Climate Change. Estimation for HWP Contribution is based on tracking carbon stock stored in wood and paper products in use and in solid-waste disposal sites (SWDS) from domestic consumption, harvests, imports, and exports. For this analysis, we hypothesize four alternative scenarios using the existing and pending U.S. energy policies by requirements for the share of biofuel to total energy consumption, and solve partial equilibrium for the U.S. timber market by 2030 for each scenario. The U.S. Forest Products Module (USFPM), created by USDA Forest Service Lab, operating within the Global Forest Products Model (GFPM) is utilized for projecting productions, supplies, and trade quantities for the U.S. timber market equilibrium. Based on those timber market components, we estimate scenario-specific HWP Contributions under the Production, the Stock Change, and the Atmospheric Approach suggested by Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories using WOODCARB II created by VTT Technical Research Centre of Finland and modified by USDA Forest Service Lab. Lastly, we compare estimated results across alternative scenarios. Results show that HWP Contributions for the baseline scenario in 2009 for all approaches are estimated higher than estimates reported by U.S. Environmental Protection Agency in 2011, (e.g., 22.64 Tg C/ year vs 14.80 Tg C/ year under the Production Approach), which is due to the economic recovery, especially in housing construction, assumed in USFPM/GFPM. Projected HWP Contribution estimates show that the Stock Change Approach, which used to provide the highest estimates before 2009, estimate HWP Contribution lowest after 2009 due to the declining annual net imports. Though fuel wood consumption is projected to be expanded as an alternative scenario requires higher wood fuel share to total energy consumption, the overall impacts on the expansion in other timber products are very modest across scenarios in USFPM/GFPM. Those negligible impacts lead to small differences of HWP Contribution estimates under all approaches across alternative scenarios. This is explained by the points that increasing logging residues are more crucial for expansion in fuel wood projections rather than the expansion of forest sector itself, and that the current HWP Contribution does not include carbon held in fuel wood products by its definition.Forest Products, Carbon Sequestration, Biofuel Policies, HWP Contribution, Resource /Energy Economics and Policy,
An effective thermodynamic potential from the instanton with Polyakov-loop contributions
We derive an effective thermodynamic potential (Omega_eff) at finite
temperature (T>0) and zero quark-chemical potential (mu_R=0), using the
singular-gauge instanton solution and Matsubara formula for N_c=3 and N_f=2 in
the chiral limit. The momentum-dependent constituent-quark mass is also
obtained as a function of T, employing the Harrington-Shepard caloron solution
in the large-N_c limit. In addition, we take into account the imaginary quark
chemical potential mu_I = A_4, translated as the traced Polayakov-loop (Phi) as
an order parameter for the Z(N_c) symmsetry, characterizing the confinement
(intact) and deconfinement (spontaneously broken) phases. As a result, we
observe the crossover of the chiral (chi) order parameter sigma^2 and Phi. It
also turns out that the critical temperature for the deconfinment phase
transition, T^Z_c is lowered by about (5-10)% in comparison to the case with a
constant constituent-quark mass. This behavior can be understood by
considerable effects from the partial chiral restoration and nontrivial QCD
vacuum on Phi. Numerical calculations show that the crossover transitions occur
at (T^chi_c,T^Z_c) ~ (216,227) MeV.Comment: 15 pages, 7 figure
Developmental functions of the P120-catenin sub-family
AbstractFor more than a decade, cell, developmental and cancer investigators have brought about a wide interest in the biology of catenin proteins, an attraction being their varied functions within differing cellular compartments. While the diversity of catenin localizations and roles has been intriguing, it has also posed a challenge to the clear interpretation of loss- or gain-of-function developmental phenotypes. The most deeply studied member of the larger catenin family is beta-catenin, whose contributions span areas including cell adhesion and intracellular signaling/ transcriptional control. More recently, attention has been directed towards p120-catenin, which in conjunction with the p120-catenin sub-family members ARVCF- and delta-catenins, are the subjects of this review. Although the requirement for vertebrate versus invertebrate p120-catenin are at variance, vertebrate p120-catenin sub-family members may each inter-link cadherin, cytoskeletal and gene regulatory functions in embryogenesis and disease
Complete quantum teleportation using nuclear magnetic resonance
Quantum mechanics provides spectacular new information processing abilities
(Bennett 1995, Preskill 1998). One of the most unexpected is a procedure called
quantum teleportation (Bennett et al 1993) that allows the quantum state of a
system to be transported from one location to another, without moving through
the intervening space. Partial implementations of teleportation (Bouwmeester et
al 1997, Boschi et al 1998) over macroscopic distances have been achieved using
optical systems, but omit the final stage of the teleportation procedure. Here
we report an experimental implementation of the full quantum teleportation
operation over inter-atomic distances using liquid state nuclear magnetic
resonance (NMR). The inclusion of the final stage enables for the first time a
teleportation implementation which may be used as a subroutine in larger
quantum computations, or for quantum communication. Our experiment also
demonstrates the use of quantum process tomography, a procedure to completely
characterize the dynamics of a quantum system. Finally, we demonstrate a
controlled exploitation of decoherence as a tool to assist in the performance
of an experiment.Comment: 15 pages, 2 figures. Minor differences between this and the published
versio
Half-integer Higher Spin Fields in (A)dS from Spinning Particle Models
We make use of O(2r+1) spinning particle models to construct linearized
higher-spin curvatures in (A)dS spaces for fields of arbitrary half-integer
spin propagating in a space of arbitrary (even) dimension: the field
potentials, whose curvatures are computed with the present models, are
spinor-tensors of mixed symmetry corresponding to Young tableaux with D/2 - 1
rows and r columns, thus reducing to totally symmetric spinor-tensors in four
dimensions. The paper generalizes similar results obtained in the context of
integer spins in (A)dS.Comment: 1+18 pages; minor changes in the notation, references updated.
Published versio
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