The Langevin Equation for a Quantum Heat Bath

We compute the quantum Langevin equation (or quantum stochastic differential equation) representing the action of a quantum heat bath at thermal equilibrium on a simple quantum system. These equations are obtained by taking the continuous limit of the Hamiltonian description for repeated quantum interactions with a sequence of photons at a given density matrix state. In particular we specialise these equations to the case of thermal equilibrium states. In the process, new quantum noises are appearing: thermal quantum noises. We discuss the mathematical properties of these thermal quantum noises. We compute the Lindblad generator associated with the action of the heat bath on the small system. We exhibit the typical Lindblad generator that provides thermalization of a given quantum system.Comment: To appear in J.F.

Fundamental solution method applied to time evolution of two energy level systems: exact and adiabatic limit results

A method of fundamental solutions has been used to investigate transitions in two energy level systems with no level crossing in a real time. Compact formulas for transition probabilities have been found in their exact form as well as in their adiabatic limit. No interference effects resulting from many level complex crossings as announced by Joye, Mileti and Pfister (Phys. Rev. {\bf A44} 4280 (1991)) have been detected in either case. It is argued that these results of this work are incorrect. However, some effects of Berry's phases are confirmed.Comment: LaTeX2e, 23 pages, 8 EPS figures. Style correcte

Adiabatic Evolution for Systems with Infinitely many Eigenvalue Crossings

We formulate an adiabatic theorem adapted to models that present an instantaneous eigenvalue experiencing an infinite number of crossings with the rest of the spectrum. We give an upper bound on the leading correction terms with respect to the adiabatic limit. The result requires only differentiability of the considered spectral projector, and some geometric hypothesis on the local behaviour of the eigenvalues at the crossings

General Adiabatic Evolution with a Gap Condition

We consider the adiabatic regime of two parameters evolution semigroups generated by linear operators that are analytic in time and satisfy the following gap condition for all times: the spectrum of the generator consists in finitely many isolated eigenvalues of finite algebraic multiplicity, away from the rest of the spectrum. The restriction of the generator to the spectral subspace corresponding to the distinguished eigenvalues is not assumed to be diagonalizable. The presence of eigenilpotents in the spectral decomposition of the generator forbids the evolution to follow the instantaneous eigenprojectors of the generator in the adiabatic limit. Making use of superadiabatic renormalization, we construct a different set of time-dependent projectors, close to the instantaneous eigeprojectors of the generator in the adiabatic limit, and an approximation of the evolution semigroup which intertwines exactly between the values of these projectors at the initial and final times. Hence, the evolution semigroup follows the constructed set of projectors in the adiabatic regime, modulo error terms we control

Rhegmatogenous retinal detachment masquerading as exudative panuveitis with intense anterior chamber inflammatory reaction.

Purpose:This is a retrospective case report illustrating the diagnostic and therapeutic challenges associated with a chronic rhegmatogenous retinal detachment masquerading as a severe panuveitis with intense anterior chamber inflammation. We have included clinical features, anterior segment and fundus photography, B-scan ultrasonography, fluorescein angiography, and intraoperative findings. Observations:A 26-year-old male presented with features of unilateral panuveitis: hypotony, anterior segment inflammation (posterior synechiae and anterior chamber cell with fibrin clumping), diffuse choroidal thickening, and retinal detachment. Laboratory investigations for infectious or rheumatologic processes were negative, and empiric systemic corticosteroid therapy was unsuccessful. This prompted suspicion for an alternate primary etiology, and pars plana vitrectomy revealed small retinal breaks as the underlying cause of the retinal detachment and inflammation. Conclusions:Rhegmatogenous retinal detachments are a known cause of intraocular inflammation. Nevertheless, it remains a challenge to recognize retinal breaks in this setting, particularly with robust anterior segment inflammation and posterior findings resembling severe exudative uveitis. Being aware of this unique presentation may prevent delays in diagnosis and have important prognostic implications

Localization for Random Unitary Operators

We consider unitary analogs of $1-$dimensional Anderson models on $l^2(\Z)$ defined by the product $U_\omega=D_\omega S$ where $S$ is a deterministic unitary and $D_\omega$ is a diagonal matrix of i.i.d. random phases. The operator $S$ is an absolutely continuous band matrix which depends on a parameter controlling the size of its off-diagonal elements. We prove that the spectrum of $U_\omega$ is pure point almost surely for all values of the parameter of $S$. We provide similar results for unitary operators defined on $l^2(\N)$ together with an application to orthogonal polynomials on the unit circle. We get almost sure localization for polynomials characterized by Verblunski coefficients of constant modulus and correlated random phases

Is there a “Gestalt bias” in indulgence? Subjectively constructing food units into wholes (versus parts) increases desire to eat and actual consumption

In the present work we extend research into the unit bias effect and its extension—the portion size effect—by demonstrating the existence of a “Gestalt bias.” Drawing on the tenets of Gestalt psychology, we show that a unit bias effect can be observed for food portions that are composed of identical basic units, but which are subjectively grouped into, or perceived as a Gestalt—a larger whole. In three studies, we find that such subjectively constructed food wholes constitute a new (perceptual) unit that is perceived bigger than the units it is constructed from, thereby prompting increased eating and desire to eat

A Study on Natural History of Variceal Bleed in an Era of Sclerotherapy.

INTRODUCTION : Portal hypertension manifesting as gastrointestinal bleed is common in 30% of cirrhotic patients, with a one year mortality of 50% after the initial bleed. The greatest risk is during the first 48 to 72 hours and more than 50% of all early rebleed episodes occur within the first 10 days after cessation of active hemorrhage. While most of the reports on the variceal bleed pattern are from the West, little information is available from the Southern states of the Indian subcontinent. A preliminary observation from our center in 2003 had shown a low rebleed rate after the index bleed. This study had a drawback of inclusion of bleeders who were already on treatment and there was probably a bias towards a low rebleed rate. The present study was undertaken to prospectively assess the variceal bleed pattern and its attendant complications amongst cirrhotics with portal hypertension. Ethics committee of Institution approved the undertaking of the study. AIMS AND OBJECTIVES : 1. To determine variceal pattern amongst south Indian patients with cirrhosis Liver. 2. To study the prevalence of recurrent bleed. 3. To study the risk factors that predicts an index bleed and subsequent bleed. CONCLUSION : Esophageal variceal bleed pattern in 205 cirrhotics were studied between January 2005 to June 2006. Age and gender did not influence the bleed pattern amongst bleeders and non bleeders. Though unknown etiology among bleeders and viral related etiology among non bleeders were common causes for cirrhosis, it was not significant. Higher grades of varices, presence of cherry red spots and fundal varices were the predictors of variceal bleed in liver cirrhosis. The risk factors that influenced the subsequent bleeds were similar to that of the initial bleed. There was no role for co-morbid diseases such as diabetes and hypertension in variceal bleed and bleed related mortality. Most of index bleeders belonged to Childs A and became Childs B following bleed. Variceal bleed related mortality following endoscopic sclerotherapy was low