Relativistic BCS-BEC Crossover at Zero Temperature

We investigate the BCS-BEC crossover at zero temperature in the frame of a relativistic model. The universality of the BCS-BEC crossover for non-relativistic systems breaks down in relativistic case and the crossover can be induced by changing the density. When the effective scattering length is much less than the fermion Compton wavelength, we recover the non-relativistic result if the gas is initially in non-relativistic state. At ultra-strong coupling where the scattering length is of the order of the Compton wavelength, a new BEC state appears. In this state the condensed bosons become nearly massless and anti-fermions are excited. The behavior of the Goldstone mode and the mixing between the amplitude and phase modes are significantly different in different condensed regions.Comment: 8 pages, 3 figures. V2: typos corrected, a comment on mean field theory adde

Spin current through an ESR quantum dot: A real-time study

The spin transport in a strongly interacting spin-pump nano-device is studied using the time-dependent variational-matrix-product-state (VMPS) approach. The precession magnetic field generates a dissipationless spin current through the quantum dot. We compute the real time spin current away from the equilibrium condition. Both transient and stationary states are reached in the simulation. The essentially exact results are compared with those from the Hartree-Fock approximation (HFA). It is found that correlation effect on the physical quantities at quasi-steady state are captured well by the HFA for small interaction strength. However the HFA misses many features in the real time dynamics. Results reported here may shed light on the understanding of the ultra-fast processes as well as the interplay of the non-equilibrium and strongly correlated effect in the transport properties.Comment: 5 pages, 5 figure

Quark and Gluon Condensates in Isospin Matter

Applying the Hellmann-Feynman theorem to a charged pion gas, the quark and gluon condensates at low isospin density are determined by precise pion properties. At intermediate density around $f_\pi^2m_\pi$, from both the estimation for the dilute pion gas and the calculation with Nambu--Jona-Lasinio model, the quark condensate is strongly and monotonously suppressed, while the gluon condensate is enhanced and can be larger than its vacuum value. This unusual behavior of the gluon condensate is universal for Bose condensed matter of mesons. Our results can be tested by lattice calculations at finite isospin density.Comment: 4 pages, 2 figures. Published version in PR

Liquid Crystal-Solid Interface Structure at the Antiferroelectric-Ferroelectric Phase Transition

Total Internal Reflection (TIR) is used to probe the molecular organization at the surface of a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. In the mixture T3, ferroelectric surface order is expelled with the bulk ferroelectric-antiferroelectric transition. The conditions for ferroelectric order at the surface of an antiferroelectric bulk are presented

Modeling soil organic carbon change in croplands of China

Using 1990 conditions, we modeled carbon (C) and nitrogen (N) biogeochemical cycles in croplands of China (and, for comparison, the United States) to estimate the annual soil organic-carbon (SOC) balance for all cropland. Overall, we estimate that China\u27s croplands lost 1.6% of their SOC (to a depth of 0.3 m) in 1990, and that U.S. cropland lost 0.1%. A key element in this difference was that ∼25% of aboveground crop residue in China was returned to the soil, compared to ∼90% in the United States. In China, SOC losses were greatest in the northeast (∼103 kg C·ha–1·yr–1), and were generally smaller (\u3c0.5 × 103 kg C·ha–1·yr–1) in regions with a longer cultivation history. Some regions showed SOC gains, generally \u3c103 kg C·ha–1·yr–1. Reduced organic-matter input to China\u27s cropland soils, and lower overall SOC levels in those soils, led to lower levels of N mineralization in the simulations, consistent with higher rates of synthetic-fertilizer application in China. C and N cycles are closely linked to soil fertility, crop yield, and non-point-source environmental pollution

The Radiative Decay of Vector Mesons

In this paper, radiative decays $\rho^0 \to \pi^+\pi^-\gamma, \pi^0\pi^0\gamma$ ,$\phi \to K^+K^-\gamma, K^0 \bar{K^0}\gamma$ are studied systematically in the U(3)_L\timesU(3)_R chiral theory of mesons. The theoretical differential spectrum with respect to photon energy and branch ratio for $\rho^0 \to \pi^+\pi^-\gamma$ agree well with the experimental data. Differential spectrums and branch ratios for $\rho^0 \to \pi^0\pi^0\gamma, \phi \to K^+ K^-\gamma,\phi \to K^0\bar{K^0}\gamma$ are predicted. The process $\phi \to K^0 \bar{K^0} \gamma$ is relevant to precision measurment of CP-violation parameters in the kaon systerm at a $\phi$-factory. We give a complete estimate of the branch ratio for this decay process by including scalar resonance $f_0, a_0$ poles, nonresonant smooth amplitude and an abnormal parity process with $K^*$ pole which hasn't been considered before. We conclude that processes with intermediate $K^*$ do not pose a potential background problem for $\phi\to K^0\bar{K}^0$ CP violation experiments.Comment: Revtex file, 12 pages, 9 eps figure

Soft Photons from Off-shell Particles in a Hot Plasma

Considering the propagation of off-shell particles in the framework of thermal field theory, we present the general formalism for the calculation of the production rate of soft photons and dileptons from a hot plasma. This approach is illustrated with an electrodynamic plasma. The photon production rate from strongly interacting quarks in the quark-gluon plasma, which might be formed in ultrarelativistic heavy ion collisions, is calculated in the previously unaccessible regime of photon energies of the order of the plasma temperature within an effective field theory incorporating dynamical chiral symmetry breaking.Comment: 8 pages in RevTeX format, 3 figures uuencoded postscript added. Also available by anonymous ftp at ftp://tpri6c.gsi.de/pub/phenning/qh95ga

There and back again: Solar cycle effects in future measurements of low-energy atmospheric neutrinos

We study the impact of time-dependent solar cycles in the atmospheric neutrino rate at DUNE and Hyper-Kamiokande (HK), focusing in particular on the flux below 1 GeV. Including the effect of neutrino oscillations for the upward-going component that travels through the Earth, we find that across the solar cycle the amplitude of time variation is about $\pm5\%$ at DUNE, and $\pm 1\%$ at HK. At DUNE, the ratio of up/down-going events ranges from 0.45 to 0.85, while at HK, it ranges from 0.75 to 1.5. Over the 11-year solar cycle, we find that the estimated statistical significance for observing time modulation of atmospheric neutrinos is $4.8\sigma$ for DUNE and $2.0\sigma$ for HK. Flux measurements at both DUNE and HK will be important for understanding systematics in the low-energy atmospheric flux as well as for understanding the effect of oscillations in low-energy atmospheric neutrinos.Comment: 6 pages (including one appendix), 5 figures. Comments welcom

Time-Dependent Gutzwiller Theory for Multiband Hubbard Models

Based on the variational Gutzwiller theory, we present a method for the computation of response functions for multiband Hubbard models with general local Coulomb interactions. The improvement over the conventional random-phase approximation is exemplified for an infinite-dimensional two-band Hubbard model where the incorporation of the local multiplet-structure leads to a much larger sensitivity of ferromagnetism on the Hund coupling. Our method can be implemented into LDA+Gutzwiller schemes and will therefore be an important tool for the computation of response functions for strongly correlated materials.Comment: 4 pages, 3 figure