Mesoscopic fluctuations of the Density of States and Conductivity in the middle of the band of Disordered Lattices

The mesoscopic fluctuations of the Density of electronic States (DoS) and of the conductivity of two- and three- dimensional lattices with randomly distributed substitutional impurities are studied. Correlations of the levels lying above (or below) the Fermi surface, in addition to the correlations of the levels lying on opposite sides of the Fermi surface, take place at half filling due to nesting. The Bragg reflections mediate to increase static fluctuations of the conductivity in the middle of the band which change the distribution function of the conductivity at half- filling.Comment: 5 pages, 3 figure

Formation of three-particle clusters in hetero-junctions and MOSFET structures

A novel interaction mechanism in MOSFET structures and $GaAs/AlGaAs$ hetero-junctions between the zone electrons of the two-dimensional (2D) gas and the charged traps on the insulator side is considered. By applying a canonical transformation, off-diagonal terms in the Hamiltonian due to the trapped level subsystem are excluded. This yields an effective three-particle attractive interaction as well as a pairing interaction inside the 2D electronic band. A type of Bethe- Goldstone equation for three particles is studied to clarify the character of the binding and the energy of the three-particle bound states. The results are used to offer a possible explanation of the Metal-Insulator transition recently observed in MOSFET and hetero-junctions.Comment: 4 page

Self-Trapping, Quantum Tunneling and Decay Rates for a Bose Gas with Attractive Nonlocal Interaction

We study the Bose-Einstein condensation for a cloud of $^7$Li atoms with attractive nonlocal (finite-range) interaction in a harmonic trap. In addition to the low-density metastable branch, that is present also in the case of local interaction, a new stable branch appears at higher densities. For a large number of atoms, the size of the cloud in the stable high-density branch is independent of the trap size and the atoms are in a macroscopic quantum self-trapped configuration. We analyze the macroscopic quantum tunneling between the low-density metastable branch and the high-density one by using the istanton technique. Moreover we consider the decay rate of the Bose condensate due to inelastic two- and three-body collisions.Comment: 5 pages, 4 figures, submitted to Phys. Rev.

Regulating atomic imbalance in double-well lattices

An insulating optical lattice with double-well sites is considered. In the case of the unity filling factor, an effective Hamiltonian in the pseudospin representation is derived. A method is suggested for manipulating the properties of the system by varying the shape of the double-well potential. In particular, it is shown that the atomic imbalance can be varied at will and a kind of the Morse-alphabet sequences can be created.Comment: Latex file, 12 pages, 3 figure

T violation and the unidirectionality of time

An increasing number of experiments at the Belle, BNL, CERN, DA{\Phi}NE and SLAC accelerators are confirming the violation of time reversal invariance (T). The violation signifies a fundamental asymmetry between the past and future and calls for a major shift in the way we think about time. Here we show that processes which violate T symmetry induce destructive interference between different paths that the universe can take through time. The interference eliminates all paths except for two that represent continuously forwards and continuously backwards time evolution. Evidence from the accelerator experiments indicates which path the universe is effectively following. This work may provide fresh insight into the long-standing problem of modeling the dynamics of T violation processes. It suggests that T violation has previously unknown, large-scale physical effects and that these effects underlie the origin of the unidirectionality of time. It may have implications for the Wheeler-DeWitt equation of canonical quantum gravity. Finally it provides a view of the quantum nature of time itself.Comment: 24 pages, 5 figures. Final version accepted for publishing in Foundations of Physics. The final publication is available at http://www.springerlink.com/content/y3h4174jw2w78322

Pair excitations and the mean field approximation of interacting Bosons, I

In our previous work \cite{GMM1},\cite{GMM2} we introduced a correction to the mean field approximation of interacting Bosons. This correction describes the evolution of pairs of particles that leave the condensate and subsequently evolve on a background formed by the condensate. In \cite{GMM2} we carried out the analysis assuming that the interactions are independent of the number of particles $N$. Here we consider the case of stronger interactions. We offer a new transparent derivation for the evolution of pair excitations. Indeed, we obtain a pair of linear equations describing their evolution. Furthermore, we obtain apriory estimates independent of the number of particles and use these to compare the exact with the approximate dynamics

Optical and Magnetooptical Spectroscopy of the Nanostructural Multilayered Films: Possible Applications

The aim of the paper is to show the potential of the spectroscopic ellipsometry and magnetooptical (MO) spectroscopy for probing of the multilayered films (MLF) with sublayer thickness of about a few nanometres. The main approach applied by us is based on the comparison of the experimental optical and MO properties with the simulated ones based on various models of the MLF. Specifically, as shown, such an approach can be useful for studying the nature of unusual MO properties and the interfaces in MLF comprising the noble and 3d-transition metals (3d-TM). The high sensitivity of the applied spectroscopic methods for the monitoring of the solid-state reactions in the 3d-TM/Si MLF induced by ion-beam treatment or by thermal annealing is also demonstrated. The optical properties of various silicides formed spontaneously or induced by various treatments at interfaces are evaluated experimentally and compared with the results of first-principle calculations.В данной работе показаны возможности спектральной эллипсометрии и магнитооптической (МО) спектроскопии для изучения структуры и особенностей физических свойств многослойных металлических пленок (МСП) с толщинами составляющих слоев порядка единиц нанометров. Основной подход исследования базируется на сравнении экспериментально измеренных оптических и МО свойств МСП с модельными, полученными для различных моделей структуры МСП. Было показано, что данный подход позволяет выяснить природу необычных МО свойств, а также структуру интерфейсной области в МСП, состоящих из слоев благородных и 3d-переходных металлов (ПМ). Также в работе продемонстрирована высокая чувствительность спектральной эллипсометрии для изучения твердотельных реакций в МСП 3d-ПМ/Si, вызванных ионной бомбардировкой или термическим отжигом. Оптические свойства различных силицидов 3d-ПМ, сформированных спонтанно либо в результате различных воздействий на МСП, были изучены экспериментально и сравнены с результатами теоретических первопринципных расчетов.В даній роботі показані можливості спектральної еліпсометрії та магнітооптичної (МО) спектроскопії для вивчення структури та особливостей фізичних властивостей багатошарових металевих плівок (БШП) з товщинами складаючих їх шарів порядку одиниць нанометрів. Основний підхід дослідження базується на порівнянні експериментально одержаних оптичних та МО властивостей БШП з модельними, що були одержані для різних моделей структури БШП. Було показано, що даний підхід дозволяє визначити природу незвичайних МО властивостей, а також природу інтерфейсної області БШП, що складаються з шарів благородних та 3d-перехідних металів (ПМ). В роботі також паказана висока чутливість спектральної еліпсометрії для вивчення твердотільних реакцій в БШП 3d-ПМ/Si, зумовлених іонним бомбардуванням або термічним відпалом. Оптичні властивості різних силіцидів 3d-ПМ, що було зформовані спонтанно або завдяки зовнішньому впливу, були вивчені експериментально та порівняні з результатами теоретичних першопринципних розрахунків

Second-order corrections to mean field evolution for weakly interacting Bosons. I

Inspired by the works of Rodnianski and Schlein and Wu, we derive a new nonlinear Schr\"odinger equation that describes a second-order correction to the usual tensor product (mean-field) approximation for the Hamiltonian evolution of a many-particle system in Bose-Einstein condensation. We show that our new equation, if it has solutions with appropriate smoothness and decay properties, implies a new Fock space estimate. We also show that for an interaction potential $v(x)= \epsilon \chi(x) |x|^{-1}$, where $\epsilon$ is sufficiently small and $\chi \in C_0^{\infty}$, our program can be easily implemented locally in time. We leave global in time issues, more singular potentials and sophisticated estimates for a subsequent part (part II) of this paper

On the Origin of Entropic Gravity and Inertia

It was recently suggested that quantum field theory is not fundamental but emerges from the loss of phase space information about matter crossing causal horizons. Possible connections between this formalism and Verlinde's entropic gravity and Jacobson's thermodynamic gravity are proposed. The holographic screen in Verlinde's formalism can be identified as local Rindler horizons and its entropy as that of the bulk fields beyond the horizons. This naturally resolves some issues on entropic gravity. The quantum fluctuation of the fields is the origin of the thermodynamic nature of entropic gravity. It is also suggested that inertia is related to dragging Rindler horizons.Comment: 9 pages, revtex4-1, 3 figures, accepted for publication in Foundations of Physic

Causality bounds for neutron-proton scattering

We consider the constraints of causality and unitarity for the low-energy interactions of protons and neutrons. We derive a general theorem that non-vanishing partial-wave mixing cannot be reproduced with zero-range interactions without violating causality or unitarity. We define and calculate interaction length scales which we call the causal range and the Cauchy-Schwarz range for all spin channels up to J = 3. For some channels we find that these length scales are as large as 5 fm. We investigate the origin of these large lengths and discuss their significance for the choice of momentum cutoff scales in effective field theory and universality in many-body Fermi systems.Comment: 36 pages, 10 figures, 7 tables, version to appear in Eur. Phys. J.