Quantum Phase Fluctuations Responsible for Pseudogap

The effect of ordering field phase fluctuations on the normal and superconducting properties of a simple 2D model with a local four-fermion attraction is studied. Neglecting the coupling between the spin and charge degrees of freedom an analytical expression has been obtained for the fermion spectral function as a single integral over a simple function. From this we show that, as the temperature increases through the 2D critical temperature and a nontrivial damping for a phase correlator develops, quantum fluctuations fill the gap in the quasiparticle spectrum. Simultaneously the quasiparticle peaks broaden significantly above the critical temperature, resembling the observed pseudogap behavior in high-T_c superconductors.Comment: 5 pages, ReVTeX, 1 EPS figure; final version to appear in Physica

Normal Coordinates Describing Coupled Oscillations in the Gravitational Field

The motion of a local source inducing small oscillations in the gravitational field is investigated and shown to exhibit pure rotational kinetic energy. Should the net affect of these slow, revolving oscillations cause large-scale rotations in spacetime it would certainly result in anomalous celestial accelerations. When this angular rotational frequency of spacetime is applied to the anomalous acceleration of the Pioneer 10/11 spacecrafts, the correlation is promising.Comment: General Relativity and Gravitation Ref.: Ms. No. GERG-D-06-00077R1 accepted for publication October 06, 200

Evaluation of the BCS Approximation for the Attractive Hubbard Model in One Dimension

The ground state energy and energy gap to the first excited state are calculated for the attractive Hubbard model in one dimension using both the Bethe Ansatz equations and the variational BCS wavefunction. Comparisons are provided as a function of coupling strength and electron density. While the ground state energies are always in very good agreement, the BCS energy gap is sometimes incorrect by an order of magnitude, particularly at half-filling. Finite size effects are also briefly discussed for cases where an exact solution in the thermodynamic limit is not possible. In general, the BCS result for the energy gap is poor compared to the exact result.Comment: 25 pages, 5 Postscript figure

Statistical Model of Superconductivity in a 2D Binary Boson-Fermion Mixture

A two-dimensional (2D) assembly of noninteracting, temperature-dependent, composite-boson Cooper pairs (CPs) in chemical and thermal equilibrium with unpaired fermions is examined in a binary boson-fermion statistical model as the superconducting singularity temperature is approached from above. The model is derived from {\it first principles} for the BCS model interfermion interaction from three extrema of the system Helmholtz free energy (subject to constant pairable-fermion number) with respect to: a) the pairable-fermion distribution function; b) the number of excited (bosonic) CPs, i.e., with nonzero total momenta--usually ignored in BCS theory--and with the appropriate (linear, as opposed to quadratic) dispersion relation that arises from the Fermi sea; and c) the number of CPs with zero total momenta. Compared with the BCS theory condensate, higher singularity temperatures for the Bose-Einstein condensate are obtained in the binary boson-fermion mixture model which are in rough agreement with empirical critical temperatures for quasi-2D superconductorsComment: 16 pages and 4 figures. This is a improved versio

Time-Like Shock Hadronization of a Supercooled Quark-Gluon Plasma

We study the energy-momentum and baryonic number conservation laws for quark-gluon plasma discontinuity transitions into hadron matter states. We find that the time-like shock hadronization of a supercooled quark-gluon plasma (when the normal vector to the discontinuity hypersurface is time-like) should take place. We consider some properties of this process, which is different from the standard space-like shock hadronization.Comment: 10 pages in Latex + 4 ps figures , preprint UP-TP 94/

A low CO2-responsive mutant of Setaria viridis reveals that reduced carbonic anhydrase limits C4 photosynthesis

In C4 species, β-carbonic anhydrase (CA), localized to the cytosol of the mesophyll cells, accelerates the interconversion of CO2 to HCO3–, the substrate used by phosphoenolpyruvate carboxylase (PEPC) in the first step of C4 photosynthesis. Here we describe the identification and characterization of low CO2-responsive mutant 1 (lcr1) isolated from an N-nitroso-N-methylurea- (NMU) treated Setaria viridis mutant population. Forward genetic investigation revealed that the mutated gene Sevir.5G247800 of lcr1 possessed a single nucleotide transition from cytosine to thymine in a β-CA gene causing an amino acid change from leucine to phenylalanine. This resulted in severe reduction in growth and photosynthesis in the mutant. Both the CO2 compensation point and carbon isotope discrimination values of the mutant were significantly increased. Growth of the mutants was stunted when grown under ambient pCO2 but recovered at elevated pCO2. Further bioinformatics analyses revealed that the mutation has led to functional changes in one of the conserved residues of the protein, situated near the catalytic site. CA transcript accumulation in the mutant was 80% lower, CA protein accumulation 30% lower, and CA activity ~98% lower compared with the wild type. Changes in the abundance of other primary C4 pathway enzymes were observed; accumulation of PEPC protein was significantly increased and accumulation of malate dehydrogenase and malic enzyme decreased. The reduction of CA protein activity and abundance in lcr1 restricts the supply of bicarbonate to PEPC, limiting C4 photosynthesis and growth. This study establishes Sevir.5G247800 as the major CA allele in Setaria for C4 photosynthesis and provides important insights into the function of CA in C4 photosynthesis that would be required to generate a rice plant with a functional C4 biochemical pathway

Phase fluctuations and pseudogap properties: influence of nonmagnetic impurities

The presence of nonmagnetic impurities in a 2D “bad” metal depresses the superconducting Berezinskii–Kosterlitz–Thouless transition temperature while leaving the pairing energy scale unchanged. Thus the region of the pseudogap nonsuperconducting phase, in which the modulus of the order parameter is nonzero but its phase is random and which arises at the pairing temperature, is substantially bigger than for the clean system. This supports the premise that fluctuations in the phase of the order parameter can in principle describe the pseudogap phenomena in high-TcTc materials over a rather wide range of temperatures and carrier densities. The temperature dependence of the bare superfluid density is also discussed