Dips in Partial Wave Amplitudes from Final State Interactions

We consider the dip-peak structures in the J=0 partial wave amplitudes for processes \gamma\gamma\rightarrow W^+W^-~ \mbox{and}~\gamma\gamma,gg\rightarrow t\overline{t} taking into account the corresponding Born term process and the rescattering process where the intermediate state is rescattered through the exchange of Higgs resonance state in the direct channel.Comment: 9 pages, CPP-93-21, 6 figures not include

Bose-Einstein Condensates in Optical Quasicrystal Lattices

We analyze the physics of Bose-Einstein condensates confined in 2D quasi-periodic optical lattices, which offer an intermediate situation between ordered and disordered systems. First, we analyze the time-of-flight interference pattern that reveals quasi-periodic long-range order. Second, we demonstrate localization effects associated with quasi-disorder as well as quasiperiodic Bloch oscillations associated with the extended nature of the wavefunction of a Bose-Einstein condensate in an optical quasicrystal. In addition, we discuss in detail the crossover between diffusive and localized regimes when the quasi-periodic potential is switched on, as well as the effects of interactions

New Lower Bound on Fermion Binding Energies

We derive a new lower bound for the ground state energy $E^{\rm F}(N,S)$ of N fermions with total spin S in terms of binding energies $E^{\rm F}(N-1,S \pm 1/2)$ of (N-1) fermions. Numerical examples are provided for some simple short-range or confining potentials.Comment: 4 pages, 1 eps figur

Cavity-induced temperature control of a two-level system

We consider a two-level atom interacting with a single mode of the electromagnetic field in a cavity within the Jaynes-Cummings model. Initially, the atom is thermal while the cavity is in a coherent state. The atom interacts with the cavity field for a fixed time. After removing the atom from the cavity and applying a laser pulse the atom will be in a thermal state again. Depending on the interaction time with the cavity field the final temperature can be varied over a large range. We discuss how this method can be used to cool the internal degrees of freedom of atoms and create heat baths suitable for studying thermodynamics at the nanoscale

Chiral two-loop pion-pion scattering parameters from crossing-symmetric constraints

Constraints on the parameters in the one- and two-loop pion-pion scattering amplitudes of standard chiral perturbation theory are obtained from explicitly crossing-symmetric sum rules. These constraints are based on a matching of the chiral amplitudes and the physical amplitudes at the symmetry point of the Mandelstam plane. The integrals over absorptive parts appearing in the sum rules are decomposed into crossing-symmetric low- and high-energy components and the chiral parameters are finally related to high-energy absorptive parts. A first application uses a simple model of these absorptive parts. The sensitivity of the results to the choice of the energy separating high and low energies is examined with care. Weak dependence on this energy is obtained as long as it stays below ~560 MeV. Reliable predictions are obtained for three two-loop parameters.Comment: 23 pages, 4 figures in .eps files, Latex (RevTex), our version of RevTex runs under Latex2.09, submitted to Phys. Rev. D,minor typographical corrections including the number at the end of the abstract, two sentences added at the end of Section 5 in answer to a referee's remar

A Hybrid Model for QCD Deconfining Phase Boundary

Intensive search for a proper and realistic equations of state (EOS) is still continued for studying the phase diagram existing between quark gluon plasma (QGP) and hadron gas (HG) phases. Lattice calculations provide such EOS for the strongly interacting matter at finite temperature ($T$) and vanishing baryon chemical potential ($\mu_{B}$). These calculations are of limited use at finite $\mu_{B}$ due to the appearance of notorious sign problem. In the recent past, we had constructed a hybrid model description for the QGP as well as HG phases where we make use of a new excluded-volume model for HG and a thermodynamically-consistent quasiparticle model for the QGP phase and used them further to get QCD phase boundary and a critical point. Since then many lattice calculations have appeared showing various thermal and transport properties of QCD matter at finite $T$ and $\mu_{B}=0$. We test our hybrid model by reproducing the entire data for strongly interacting matter and predict our results at finite $\mu_{B}$ so that they can be tested in future. Finally we demonstrate the utility of the model in fixing the precise location, the order of the phase transition and the nature of CP existing on the QCD phase diagram. We thus emphasize the suitability of the hybrid model as formulated here in providing a realistic EOS for the strongly interacting matter.Comment: 22 pages, 10 figures. corrected version published in Physical Review D. arXiv admin note: substantial text overlap with arXiv:1201.044

A systematic correlation between two-dimensional flow topology and the abstract statistics of turbulence

Velocity differences in the direct enstrophy cascade of two-dimensional turbulence are correlated with the underlying flow topology. The statistics of the transverse and longitudinal velocity differences are found to be governed by different structures. The wings of the transverse distribution are dominated by strong vortex centers, whereas, the tails of the longitudinal differences are dominated by saddles. Viewed in the framework of earlier theoretical work this result suggests that the transfer of enstrophy to smaller scales is accomplished in regions of the flow dominated by saddles.Comment: 4 pages, 4 figure

Determination of hadronic partial widths for scalar-isoscalar resonances f0(980), f0(1300), f0(1500), f_0(1750) and the broad state f0(1530^{+90}_{-250})

In the article of V.V. Anisovich et al., Yad. Fiz. 63, 1489 (2000), the K-matrix solutions for the wave IJ^{PC}=00^{++} were obtained in the mass region 450 - 1900 MeV where four resonances f0(980), f0(1300), f0(1500), f0(1750) and the broad state f0(1530^{+90}_{-250}) are located. Based on these solutions, we determine partial widths for scalar-isoscalar states decaying into the channels pi-pi, K-anti K, eta-eta, eta-eta', pi-pi-pi-pi and corresponding decay couplings.Comment: Some typos were correcte

Graduate Quantum Mechanics Reform

We address four main areas in which graduate quantum mechanics education can be improved: course content, textbook, teaching methods, and assessment tools. We report on a three year longitudinal study at the Colorado School of Mines using innovations in all these areas. In particular, we have modified the content of the course to reflect progress in the field in the last 50 years, used textbooks that include such content, incorporated a variety of teaching techniques based on physics education research, and used a variety of assessment tools to study the effectiveness of these reforms. We present a new assessment tool, the Graduate Quantum Mechanics Conceptual Survey, and further testing of a previously developed assessment tool, the Quantum Mechanics Conceptual Survey. We find that graduate students respond well to research-based techniques that have been tested mainly in introductory courses, and that they learn much of the new content introduced in each version of the course. We also find that students' ability to answer conceptual questions about graduate quantum mechanics is highly correlated with their ability to solve calculational problems on the same topics. In contrast, we find that students' understanding of basic undergraduate quantum mechanics concepts at the modern physics level is not improved by instruction at the graduate level.Comment: accepted to American Journal of Physic