Extinctions and Correlations for Uniformly Discrete Point Processes with Pure Point Dynamical Spectra

The paper investigates how correlations can completely specify a uniformly discrete point process. The setting is that of uniformly discrete point sets in real space for which the corresponding dynamical hull is ergodic. The first result is that all of the essential physical information in such a system is derivable from its $n$-point correlations, $n= 2, 3, >...$. If the system is pure point diffractive an upper bound on the number of correlations required can be derived from the cycle structure of a graph formed from the dynamical and Bragg spectra. In particular, if the diffraction has no extinctions, then the 2 and 3 point correlations contain all the relevant information.Comment: 16 page

Spin wave excitations: The main source of the temperature dependence of Interlayer exchange coupling in nanostructures

Quantum mechanical calculations based on an extended Heisenberg model are compared with ferromagnetic resonance (FMR) experiments on prototype trilayer systems Ni_7/Cu_n/Co_2/Cu(001) in order to determine and separate for the first time quantitatively the sources of the temperature dependence of interlayer exchange coupling. Magnon excitations are responsible for about 75% of the reduction of the coupling strength from zero to room temperature. The remaining 25% are due to temperature effects in the effective quantum well and the spacer/magnet interfaces.Comment: accepted for publication in PR

Deformed Gaussian Orthogonal Ensemble Analysis of the Interacting Boson Model

A Deformed Gaussian Orthogonal Ensemble (DGOE) which interpolates between the Gaussian Orthogonal Ensemble and a Poissonian Ensemble is constructed. This new ensemble is then applied to the analysis of the chaotic properties of the low lying collective states of nuclei described by the Interacting Boson Model (IBM). This model undergoes a transition order-chaos-order from the $SU(3)$ limit to the $O(6)$ limit. Our analysis shows that the quantum fluctuations of the IBM Hamiltonian, both of the spectrum and the eigenvectors, follow the expected behaviour predicted by the DGOE when one goes from one limit to the other.Comment: 10 pages, 4 figures (avaiable upon request), IFUSP/P-1086 Replaced version: in the previous version the name of one of the authors was omitte

QCD near the Light Cone

Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near light cone coordinates. We study the dynamics of the gluonic zero modes of this Hamiltonian. The strong coupling solutions serve as a basis for the complete problem. We discuss the importance of zero modes for the confinement mechanism.Comment: 32 pages, ReVTeX, 2 Encapsulated PostScript figure

KIC 10080943: a binary star with two γ Doradus/δ Scuti hybrid pulsators. Analysis of the g modes

We use 4 yr of Kepler photometry to study the non-eclipsing spectroscopic binary KIC 10080943. We find both components to be γ Doradus/δ Scuti hybrids, which pulsate in both p and g modes. We present an analysis of the g modes, which is complicated by the fact that the two sets of l = 1 modes partially overlap in the frequency spectrum. Nevertheless, it is possible to disentangle them by identifying rotationally split doublets from one component and triplets from the other. The identification is helped by the presence of additive combina- tion frequencies in the spectrum that involve the doublets but not the triplets. The rotational splittings of the multiplets imply core rotation periods of about 11 and 7 d in the two stars. One of the stars also shows evidence of l = 2 modes

Local Spectral Density for a Periodically Driven System of Coupled Quantum States with Strong Imperfection in Unperturbed Energies

A random matrix theory approach is applied in order to analyze the localization properties of local spectral density for a generic system of coupled quantum states with strong static imperfection in the unperturbed energy levels. The system is excited by an external periodic field, the temporal profile of which is close to monochromatic one. The shape of local spectral density is shown to be well described by the contour obtained from a relevant model of periodically driven two-states system with irreversible losses to an external thermal bath. The shape width and the inverse participation ratio are determined as functions both of the Rabi frequency and of parameters specifying the localization effect for our system in the absence of external field.Comment: 6 pages, 5 figures, submitted to Optics and Spectroscop

Vacuum Structures of Supersymmetric Yang-Mills Theories in 1+11+1 Dimensions

Vacuum structures of supersymmetric (SUSY) Yang-Mills theories in $1+1$ dimensions are studied with the spatial direction compactified. SUSY allows only periodic boundary conditions for both fermions and bosons. By using the Born-Oppenheimer approximation for the weak coupling limit, we find that the vacuum energy vanishes, and hence the SUSY is unbroken. Other boundary conditions are also studied, especially the antiperiodic boundary condition for fermions which is related to the system in finite temperatures. In that case we find for gaugino bilinears a nonvanishing vacuum condensation which indicates instanton contributions.Comment: LaTeX file, 25 page, 3 eps figure, some references adde

(1+1)-Dimensional Yang-Mills Theory Coupled to Adjoint Fermions on the Light Front

We consider SU(2) Yang-Mills theory in 1+1 dimensions coupled to massless adjoint fermions. With all fields in the adjoint representation the gauge group is actually SU(2)/Z_2, which possesses nontrivial topology. In particular, there are two distinct topological sectors and the physical vacuum state has a structure analogous to a \theta vacuum. We show how this feature is realized in light-front quantization, with periodicity conditions used to regulate the infrared and treating the gauge field zero mode as a dynamical quantity. We find expressions for the degenerate vacuum states and construct the analog of the \theta vacuum. We then calculate the bilinear condensate in the model. We argue that the condensate does not affect the spectrum of the theory, although it is related to the string tension that characterizes the potential between fundamental test charges when the dynamical fermions are given a mass. We also argue that this result is fundamentally different from calculations that use periodicity conditions in x^1 as an infrared regulator.Comment: 20 pages, Revte

Static interactions and stability of matter in Rindler space

Dynamical issues associated with quantum fields in Rindler space are addressed in a study of the interaction between two sources at rest generated by the exchange of scalar particles, photons and gravitons. These static interaction energies in Rindler space are shown to be scale invariant, complex quantities. The imaginary part will be seen to have its quantum mechanical origin in the presence of an infinity of zero modes in uniformly accelerated frames which in turn are related to the radiation observed in inertial frames. The impact of a uniform acceleration on the stability of matter and the properties of particles is discussed and estimates are presented of the instability of hydrogen atoms when approaching the horizon.Comment: 28 pages, 4 figure

Stopping Light All-Optically

We show that light pulses can be stopped and stored all-optically, with a process that involves an adiabatic and reversible pulse bandwidth compression occurring entirely in the optical domain. Such a process overcomes the fundamental bandwidth-delay constraint in optics, and can generate arbitrarily small group velocities for light pulses with a given bandwidth, without the use of any coherent or resonant light-matter interactions. We exhibit this process in optical resonator systems, where the pulse bandwidth compression is accomplished only by small refractive index modulations performed at moderate speeds. (Accepted for publication in Phys. Rev. Lett. Submitted on Sept. 10th 2003)Comment: 18 pages including 3 figures. Accepted for publication in Phys. Rev. Let