Symmetries of hadrons after unbreaking the chiral symmetry

We study hadron correlators upon artificial restoration of the spontaneously broken chiral symmetry. In a dynamical lattice simulation we remove the lowest lying eigenmodes of the Dirac operator from the valence quark propagators and study evolution of the hadron masses obtained. All mesons and baryons in our study, except for a pion, survive unbreaking the chiral symmetry and their exponential decay signals become essentially better. From the analysis of the observed spectroscopic patterns we conclude that confinement still persists while the chiral symmetry is restored. All hadrons fall into different chiral multiplets. The broken U(1)_A symmetry does not get restored upon unbreaking the chiral symmetry. We also observe signals of some higher symmetry that includes chiral symmetry as a subgroup. Finally, from comparison of the \Delta - N splitting before and after unbreaking of the chiral symmetry we conclude that both the color-magnetic and the flavor-spin quark-quark interactions are of equal importance.Comment: 12 pages, 14 figures; final versio

Monte Carlo simulation of SU(2) gauge theory with fermions on a four-dimensional lattice

After integration over the fermions in an SU(2) lattice gauge theory, the effective fermionic action may be expressed as a sum over all possible closed gauge field loops with corresponding weight factors. We approximate this sum and perform a Monte Carlo simulation of a coupled fermion-gauge system on a 44 lattice. We compare our results for left angle bracketSeffright-pointing angle bracket and Image for different values of the gauge field coupling β and fermion coupling κ with the free fermion theory on a lattice. left angle bracketSeffright-pointing angle bracket turns out to be quite small for Image

Monte Carlo evaluation of path integrals for the nuclear shell model

We present in detail a formulation of the shell model as a path integral and Monte Carlo techniques for its evaluation. The formulation, which linearizes the two-body interaction by an auxiliary field, is quite general, both in the form of the effective `one-body' Hamiltonian and in the choice of ensemble. In particular, we derive formulas for the use of general (beyond monopole) pairing operators, as well as a novel extraction of the canonical (fixed-particle number) ensemble via an activity expansion. We discuss the advantages and disadvantages of the various formulations and ensembles and give several illustrative examples. We also discuss and illustrate calculation of the imaginary-time response function and the extraction, by maximum entropy methods, of the corresponding strength function. Finally, we discuss the "sign-problem" generic to fermion Monte Carlo calculations, and prove that a wide class of interactions are free of this limitation.Comment: 38 pages, RevTeX v3.0, figures available upon request; Caltech Preprint #MAP-15

Influence of Anomalous Dispersion on Optical Characteristics of Quantum Wells

Frequency dependencies of optical characteristics (reflection, transmission and absorption of light) of a quantum well are investigated in a vicinity of interband resonant transitions in a case of two closely located excited energy levels. A wide quantum well in a quantizing magnetic field directed normally to the quantum-well plane, and monochromatic stimulating light are considered. Distinctions between refraction coefficients of barriers and quantum well, and a spatial dispersion of the light wave are taken into account. It is shown that at large radiative lifetimes of excited states in comparison with nonradiative lifetimes, the frequency dependence of the light reflection coefficient in the vicinity of resonant interband transitions is defined basically by a curve, similar to the curve of the anomalous dispersion of the refraction coefficient. The contribution of this curve weakens at alignment of radiative and nonradiative times, it is practically imperceptible at opposite ratio of lifetimes . It is shown also that the frequency dependencies similar to the anomalous dispersion do not arise in transmission and absorption coefficients.Comment: 10 pages, 6 figure

Profile alterations of a symmetrical light pulse coming through a quantum well

The theory of a response of a two-energy-level system, irradiated by symmetrical light pulses, has been developed.(Suchlike electronic system approximates under the definite conditions a single ideal quantum well (QW) in a strong magnetic field {\bf H}, directed perpendicularly to the QW's plane, or in magnetic field absence.) The general formulae for the time-dependence of non-dimensional reflection {\cal R}(t), absorption {\cal A}(t) and transmission {\cal T}(t) of a symmetrical light pulse have been obtained. It has been shown that the singularities of three types exist on the dependencies {\cal R}(t), {\cal A}(t), {\cal T}(t). The oscillating time dependence of {\cal R}(t), {\cal A}(t), {\cal T}(t) on the detuning frequency \Delta\omega=\omega_l-\omega_0 takes place. The oscillations are more easily observable when \Delta\omega\simeq\gamma_l. The positions of the total absorption, reflection and transparency singularities are examined when the frequency \omega_l is detuned.Comment: 9 pages, 13 figures with caption

Hyperfine, rotational and Zeeman structure of the lowest vibrational levels of the 87^{87}Rb2_2 \tripletex state

We present the results of an experimental and theoretical study of the electronically excited \tripletex state of $^{87}$Rb$_2$ molecules. The vibrational energies are measured for deeply bound states from the bottom up to $v'=15$ using laser spectroscopy of ultracold Rb$_2$ Feshbach molecules. The spectrum of each vibrational state is dominated by a 47\,GHz splitting into a \cog and \clg component caused mainly by a strong second order spin-orbit interaction. Our spectroscopy fully resolves the rotational, hyperfine, and Zeeman structure of the spectrum. We are able to describe to first order this structure using a simplified effective Hamiltonian.Comment: 10 pages, 7 figures, 2 table

Single-particle and Interaction Effects on the Cohesion and Transport and Magnetic Properties of Metal Nanowires at Finite Voltages

The single-particle and interaction effects on the cohesion, electronic transport, and some magnetic properties of metallic nanocylinders have been studied at finite voltages by using a generalized mean-field electron model. The electron-electron interactions are treated in the self-consistent Hartree approximation. Our results show the single-particle effect is dominant in the cohesive force, while the nonzero magnetoconductance and magnetotension coefficients are attributed to the interaction effect. Both single-particle and interaction effects are important to the differential conductance and magnetic susceptibility.Comment: 5 pages, 6 figure

Extinction toward the Compact HII Regions G-0.02-0.07

The four HII regions in the Sgr A East complex: A, B, C, and D, represent evidence of recent massive star formation in the central ten parsecs. Using Paschen-alpha images taken with HST and 8.4 GHz VLA data, we construct an extinction map of A-D, and briefly discuss their morphology and location.Comment: 2 pages, 1 figure. To be published in the Astronomical Society of the Pacific Conference Series Proceedings of the Galactic Center Workshop 2009, Shangha