Variational Methods for Path Integral Scattering
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Solving the Quantum Scattering Problem for Systems of Two and Three Charged Particles
Solving the quantum scattering problem for systems of two and three charged particles Solving the quantum scattering problem for systems of two and three charged particles Mikhail Volkov c Mikhail Volkov, Stockholm 2011 ISBN 978-91-7447-213-4 Printed in Sweden by Universitetsservice US-AB, Stockholm 2011 Distributor: Department of Physics, Stockholm University In memory of Professor Valentin Ostrovsky Abstract A rigorous formalism for solving the Coulomb scattering problem is presented in this thesis. The approach is based on splitting the interaction potential into a finite-range part and a long-range tail part. In this representation the scattering problem can be reformulated to one which is suitable for applying exterior complex scaling. The scaled problem has zero boundary conditions at infinity and can be implemented numerically for finding scattering amplitudes. The systems under consideration may consist of two or three charged particles. The technique presented in this thesis is first developed for the case of a two body single channel Coulomb scattering problem. The method is mathe- matically validated for the partial wave formulation of the scattering problem. Integral and local representations for the partial wave scattering amplitudes have been derived. The partial wave results are summed up to obtain the scat- tering amplitude for the three dimensional scattering problem. The approach is generalized to allow the two body multichannel scattering problem to be solved. The theoretical results are illustrated with numerical calculations for a number of models. Finally, the potential splitting technique is further developed and validated for the three body Coulomb scattering problem. It is shown that only a part of the total interaction potential should be split to obtain the inhomogeneous equation required such that the method of exterior complex scaling can be applied. -
José M. Vega-Guzmán
Jos´eM. Vega-Guzm´an Curriculum Vitae Contact Department of Mathematics Tel: (409) 880-8792 Information College of Arts and Sciences Fax: (409) 880-8794 Lamar University email: [email protected] 200-C Lucas Building URL: https://sites.google.com/site/profjmvg/ Beaumont, TX 77710 Education PhD (Applied Mathematics) 2008{2013 • Arizona State University, Tempe, AZ • Co-Advisors: Sergei K. Suslov and Carlos Castillo-Chavez • Dissertation Title: Solution Methods for Certain Evolution Equations Master in Natural Sciences (Mathematics) 2006{2008 • Arizona State University, Tempe, AZ B.S. (MathEd) 2000{2005 • Universidad de Puerto Rico, Cayey, PR • Advisor: Maria A. Avi~n´o Research Interests Nonlinear Wave Propagation. Quantum Mechanics. Integrability of Nonlinear Evolution Equations. Applications of ODE's and PDE's in the Natural Sciences. Mathematical Modeling. Publications 2017 Vega{Guzm´an,J.M.; Alqahtani, R.; Zhou, Q.; Mahmood, M.F.; Moshokoa, S.P.; Ullah, M.Z.; Biswas, A.; Belic, M. Optical solitons for Lakshmanan-Porsezian-Daniel model with spatio-temporal dispersion using the method of undetermined coefficients. Optik - International Journal for Light and Electron Optics. 144, 115{123. 2017 Wang, G.; Kara, A.H.; Vega{Guzm´an,J.M.; Biswas, A. Group analysis, nonlinear self-adjointness, conser- vation laws and soliton solutions for the mKdV systems. Nonlinear Analysis: Modeling and Control. 22(3), 334{346. 2017 Vega{Guzm´an,J.M.; Ullah, M.Z.; Asma, M.; Zhou, Q.; Biswas, A. Dispersive solitons in magneto-optic waveguides. Superlattices and Microstructures. 103, 161{170. 2017 Vega{Guzm´an,J.M.; Mahmood, M.F.; Zhou, Q.; Triki, H.; Arnous, A.H.; Biswas, A.; Moshokoa, S.P.; Belic, M. -
Introduction to the Modern Calculus of Variations
MA4G6 Lecture Notes Introduction to the Modern Calculus of Variations Filip Rindler Spring Term 2015 Filip Rindler Mathematics Institute University of Warwick Coventry CV4 7AL United Kingdom [email protected] http://www.warwick.ac.uk/filiprindler Copyright ©2015 Filip Rindler. Version 1.1. Preface These lecture notes, written for the MA4G6 Calculus of Variations course at the University of Warwick, intend to give a modern introduction to the Calculus of Variations. I have tried to cover different aspects of the field and to explain how they fit into the “big picture”. This is not an encyclopedic work; many important results are omitted and sometimes I only present a special case of a more general theorem. I have, however, tried to strike a balance between a pure introduction and a text that can be used for later revision of forgotten material. The presentation is based around a few principles: • The presentation is quite “modern” in that I use several techniques which are perhaps not usually found in an introductory text or that have only recently been developed. • For most results, I try to use “reasonable” assumptions, not necessarily minimal ones. • When presented with a choice of how to prove a result, I have usually preferred the (in my opinion) most conceptually clear approach over more “elementary” ones. For example, I use Young measures in many instances, even though this comes at the expense of a higher initial burden of abstract theory. • Wherever possible, I first present an abstract result for general functionals defined on Banach spaces to illustrate the general structure of a certain result. -
On the Ekeland Variational Principle with Applications and Detours
Lectures on The Ekeland Variational Principle with Applications and Detours By D. G. De Figueiredo Tata Institute of Fundamental Research, Bombay 1989 Author D. G. De Figueiredo Departmento de Mathematica Universidade de Brasilia 70.910 – Brasilia-DF BRAZIL c Tata Institute of Fundamental Research, 1989 ISBN 3-540- 51179-2-Springer-Verlag, Berlin, Heidelberg. New York. Tokyo ISBN 0-387- 51179-2-Springer-Verlag, New York. Heidelberg. Berlin. Tokyo No part of this book may be reproduced in any form by print, microfilm or any other means with- out written permission from the Tata Institute of Fundamental Research, Colaba, Bombay 400 005 Printed by INSDOC Regional Centre, Indian Institute of Science Campus, Bangalore 560012 and published by H. Goetze, Springer-Verlag, Heidelberg, West Germany PRINTED IN INDIA Preface Since its appearance in 1972 the variational principle of Ekeland has found many applications in different fields in Analysis. The best refer- ences for those are by Ekeland himself: his survey article [23] and his book with J.-P. Aubin [2]. Not all material presented here appears in those places. Some are scattered around and there lies my motivation in writing these notes. Since they are intended to students I included a lot of related material. Those are the detours. A chapter on Nemyt- skii mappings may sound strange. However I believe it is useful, since their properties so often used are seldom proved. We always say to the students: go and look in Krasnoselskii or Vainberg! I think some of the proofs presented here are more straightforward. There are two chapters on applications to PDE. -
Zero-Point Energy of Ultracold Atoms
Zero-point energy of ultracold atoms Luca Salasnich1,2 and Flavio Toigo1 1Dipartimento di Fisica e Astronomia “Galileo Galilei” and CNISM, Universit`adi Padova, via Marzolo 8, 35131 Padova, Italy 2CNR-INO, via Nello Carrara, 1 - 50019 Sesto Fiorentino, Italy Abstract We analyze the divergent zero-point energy of a dilute and ultracold gas of atoms in D spatial dimensions. For bosonic atoms we explicitly show how to regularize this divergent contribution, which appears in the Gaussian fluctuations of the functional integration, by using three different regular- ization approaches: dimensional regularization, momentum-cutoff regular- ization and convergence-factor regularization. In the case of the ideal Bose gas the divergent zero-point fluctuations are completely removed, while in the case of the interacting Bose gas these zero-point fluctuations give rise to a finite correction to the equation of state. The final convergent equa- tion of state is independent of the regularization procedure but depends on the dimensionality of the system and the two-dimensional case is highly nontrivial. We also discuss very recent theoretical results on the divergent zero-point energy of the D-dimensional superfluid Fermi gas in the BCS- BEC crossover. In this case the zero-point energy is due to both fermionic single-particle excitations and bosonic collective excitations, and its regu- larization gives remarkable analytical results in the BEC regime of compos- ite bosons. We compare the beyond-mean-field equations of state of both bosons and fermions with relevant experimental data on dilute and ultra- cold atoms quantitatively confirming the contribution of zero-point-energy quantum fluctuations to the thermodynamics of ultracold atoms at very low temperatures. -
Discrete Variable Representations and Sudden Models in Quantum
Volume 89. number 6 CHLMICAL PHYSICS LEITERS 9 July 1981 DISCRETEVARlABLE REPRESENTATIONS AND SUDDEN MODELS IN QUANTUM SCATTERING THEORY * J.V. LILL, G.A. PARKER * and J.C. LIGHT l7re JarrresFranc/t insrihrre and The Depwrmcnr ofC7temtsrry. Tire llm~crsrry of Chrcago. Otrcago. l7lrrrors60637. USA Received 26 September 1981;m fin11 form 29 May 1982 An c\act fOrmhSm In which rhe scarrcnng problem may be descnbcd by smsor coupled cqumons hbclcd CIIIW bb bans iuncltons or quadrature pomts ISpresented USCof each frame and the srnrplyculuatcd unitary wmsformatlon which connects them resulis III an cfliclcnt procedure ror pcrrormrnpqu~nrum scxrcrrn~ ca~cubr~ons TWO ~ppro~mac~~~ arc compxcd wrh ihe IOS. 1. Introduction “ergenvalue-like” expressions, rcspcctnely. In each case the potential is represented by the potcntud Quantum-mechamcal scattering calculations are function Itself evahrated at a set of pomts. most often performed in the close-coupled representa- Whjle these models have been shown to be cffcc- tion (CCR) in which the internal degrees of freedom tive III many problems,there are numerousambiguities are expanded in an appropnate set of basis functions in their apphcation,especially wtth regardto the resulting in a set of coupled diiierentral equations UI choice of constants. Further, some models possess the scattering distance R [ 1,2] _The method is exact formal difficulties such as loss of time reversal sym- IO w&in a truncation error and convergence is ob- metry, non-physical coupling, and non-conservation tained by increasing the size of the basis and hence the of energy and momentum [ 1S-191. In fact, it has number of coupled equations (NJ While considerable never been demonstrated that sudden models fit into progress has been madein the developmentof efficient any exactframework for solutionof the scattering algonthmsfor the solunonof theseequations [3-71, problem. -
The S-Matrix Formulation of Quantum Statistical Mechanics, with Application to Cold Quantum Gas
THE S-MATRIX FORMULATION OF QUANTUM STATISTICAL MECHANICS, WITH APPLICATION TO COLD QUANTUM GAS A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Pye Ton How August 2011 c 2011 Pye Ton How ALL RIGHTS RESERVED THE S-MATRIX FORMULATION OF QUANTUM STATISTICAL MECHANICS, WITH APPLICATION TO COLD QUANTUM GAS Pye Ton How, Ph.D. Cornell University 2011 A novel formalism of quantum statistical mechanics, based on the zero-temperature S-matrix of the quantum system, is presented in this thesis. In our new formalism, the lowest order approximation (“two-body approximation”) corresponds to the ex- act resummation of all binary collision terms, and can be expressed as an integral equation reminiscent of the thermodynamic Bethe Ansatz (TBA). Two applica- tions of this formalism are explored: the critical point of a weakly-interacting Bose gas in two dimensions, and the scaling behavior of quantum gases at the unitary limit in two and three spatial dimensions. We found that a weakly-interacting 2D Bose gas undergoes a superfluid transition at T 2πn/[m log(2π/mg)], where n c ≈ is the number density, m the mass of a particle, and g the coupling. In the unitary limit where the coupling g diverges, the two-body kernel of our integral equation has simple forms in both two and three spatial dimensions, and we were able to solve the integral equation numerically. Various scaling functions in the unitary limit are defined (as functions of µ/T ) and computed from the numerical solutions. -
The Original Euler's Calculus-Of-Variations Method: Key
Submitted to EJP 1 Jozef Hanc, [email protected] The original Euler’s calculus-of-variations method: Key to Lagrangian mechanics for beginners Jozef Hanca) Technical University, Vysokoskolska 4, 042 00 Kosice, Slovakia Leonhard Euler's original version of the calculus of variations (1744) used elementary mathematics and was intuitive, geometric, and easily visualized. In 1755 Euler (1707-1783) abandoned his version and adopted instead the more rigorous and formal algebraic method of Lagrange. Lagrange’s elegant technique of variations not only bypassed the need for Euler’s intuitive use of a limit-taking process leading to the Euler-Lagrange equation but also eliminated Euler’s geometrical insight. More recently Euler's method has been resurrected, shown to be rigorous, and applied as one of the direct variational methods important in analysis and in computer solutions of physical processes. In our classrooms, however, the study of advanced mechanics is still dominated by Lagrange's analytic method, which students often apply uncritically using "variational recipes" because they have difficulty understanding it intuitively. The present paper describes an adaptation of Euler's method that restores intuition and geometric visualization. This adaptation can be used as an introductory variational treatment in almost all of undergraduate physics and is especially powerful in modern physics. Finally, we present Euler's method as a natural introduction to computer-executed numerical analysis of boundary value problems and the finite element method. I. INTRODUCTION In his pioneering 1744 work The method of finding plane curves that show some property of maximum and minimum,1 Leonhard Euler introduced a general mathematical procedure or method for the systematic investigation of variational problems. -
(2021) Transmon in a Semi-Infinite High-Impedance Transmission Line
PHYSICAL REVIEW RESEARCH 3, 023003 (2021) Transmon in a semi-infinite high-impedance transmission line: Appearance of cavity modes and Rabi oscillations E. Wiegand ,1,* B. Rousseaux ,2 and G. Johansson 1 1Applied Quantum Physics Laboratory, Department of Microtechnology and Nanoscience-MC2, Chalmers University of Technology, 412 96 Göteborg, Sweden 2Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France (Received 8 December 2020; accepted 11 March 2021; published 1 April 2021) In this paper, we investigate the dynamics of a single superconducting artificial atom capacitively coupled to a transmission line with a characteristic impedance comparable to or larger than the quantum resistance. In this regime, microwaves are reflected from the atom also at frequencies far from the atom’s transition frequency. Adding a single mirror in the transmission line then creates cavity modes between the atom and the mirror. Investigating the spontaneous emission from the atom, we then find Rabi oscillations, where the energy oscillates between the atom and one of the cavity modes. DOI: 10.1103/PhysRevResearch.3.023003 I. INTRODUCTION [43]. Furthermore, high-impedance resonators make it pos- sible for light-matter interaction to reach strong-coupling In the past two decades, circuit quantum electrodynamics regimes due to strong coupling to vacuum fluctuations [44]. (circuit QED) has become a field of growing interest for quan- In this article, we investigate the spontaneous emission tum information processing and also to realize new regimes of a transmon [45] capacitively coupled to a 1D TL that is in quantum optics [1–11]. -
Subdifferential Test for Optimality
Subdifferential Test for Optimality Florence JULES and Marc LASSONDE Universit´edes Antilles et de la Guyane 97159 Pointe `aPitre, France E-mail: fl[email protected], [email protected] Abstract. We provide a first-order necessary and sufficient condition for optimality of lower semicontinuous functions on Banach spaces using the concept of subdifferential. From the sufficient condition we derive that any subdifferential operator is monotone absorbing, hence maximal monotone when the function is convex. Keywords: lower semicontinuity, subdifferential, directional derivative, first-order condition, optimality criterion, maximal monotonicity. 2010 Mathematics Subject Classification: 49J52, 49K27, 26D10, 26B25. 1 Introduction First-order sufficient conditions for optimality in terms of derivatives or directional derivatives are well known. Typical such conditions are variants of Minty variational inequalities. Let us quote for example the following simple result (see [3]): Let f be a real-valued function which is continuous on a neighbourhood D centred at a in Rn and differentiable on D \ {a}. Then, f has a local minimum value at a if (x − a) ·∇f(x) > 0 for all x ∈ D \ {a}. For first-order conditions in terms of directional derivatives, we refer to [5]. The main objective of this note is to establish a necessary and sufficient condition for optimality of nonsmooth lower semicontinuous functions on Banach spaces using subdiffer- entials. To this end, we first provide a link between the directional derivative of a function and its dual companion represented by the subdifferential (Theorem 2.1). Then, we prove a sharp version of the mean value inequality for lower semicontinuous function using directional derivative (Lemma 3.1). -
8 the Variational Principle
8 The Variational Principle 8.1 Approximate solution of the Schroedinger equation If we can’t find an analytic solution to the Schroedinger equation, a trick known as the varia- tional principle allows us to estimate the energy of the ground state of a system. We choose an unnormalized trial function Φ(an) which depends on some variational parameters, an and minimise hΦ|Hˆ |Φi E[a ] = n hΦ|Φi with respect to those parameters. This gives an approximation to the wavefunction whose accuracy depends on the number of parameters and the clever choice of Φ(an). For more rigorous treatments, a set of basis functions with expansion coefficients an may be used. The proof is as follows, if we expand the normalised wavefunction 1/2 |φ(an)i = Φ(an)/hΦ(an)|Φ(an)i in terms of the true (unknown) eigenbasis |ii of the Hamiltonian, then its energy is X X X ˆ 2 2 E[an] = hφ|iihi|H|jihj|φi = |hφ|ii| Ei = E0 + |hφ|ii| (Ei − E0) ≥ E0 ij i i ˆ where the true (unknown) ground state of the system is defined by H|i0i = E0|i0i. The inequality 2 arises because both |hφ|ii| and (Ei − E0) must be positive. Thus the lower we can make the energy E[ai], the closer it will be to the actual ground state energy, and the closer |φi will be to |i0i. If the trial wavefunction consists of a complete basis set of orthonormal functions |χ i, each P i multiplied by ai: |φi = i ai|χii then the solution is exact and we just have the usual trick of expanding a wavefunction in a basis set. -
Lectures on Partial Differential Equations
Lectures on Partial Differential Equations Govind Menon1 Dec. 2005 Abstract These are my incomplete lecture notes for the graduate introduction to PDE at Brown University in Fall 2005. The lectures on Laplace’s equation and the heat equation are included here. Typing took too much work after that. I hope what is here is still useful. Andreas Kl¨ockner’s transcript of the remaining lectures is also posted on my website. Those however have not been proofread. Comments are wel- come by email. Contents 1 Laplace’s equation 3 1.1 Introduction............................ 3 1.1.1 Minimal surfaces and Laplace’s equation . 3 1.1.2 Fields and Laplace’s equation . 5 1.1.3 Motivation v. Results . 5 1.2 Notation.............................. 5 1.3 Themeanvalueinequality. 6 1.4 Maximumprinciples ....................... 8 1.5 Thefundamentalsolution . 10 1.6 Green’s function and Poisson’s integral formula . 13 1.7 The mean value property revisited . 17 1.8 Harmonic functions are analytic . 17 1.9 Compactness and convergence . 21 1.10 Perron’s method for the Dirichlet problem . 22 1.11 Energy methods and Dirichlet’s principle . 26 1.12 Potentials of measures . 28 1.13 Lebesgue’sthorn .. .. .. .. .. .. .. 30 1.14 The potential of a compact set . 33 1.15 Capacity of compact sets . 37 1 2 1.16 Variational principles for capacity . 39 2 The heat equation 43 2.1 Motivation ............................ 43 2.2 Thefundamentalsolution . 43 2.3 Uniquenessofsolutions . 47 2.4 Theweakmaximumprinciple . 48 2.5 Themeanvalueproperty . 49 2.6 Thestrongmaximumprinciple . 53 2.7 Differenceschemes . .. .. .. .. .. .. 54 2.8 Randomwalks .......................... 56 2.9 Brownianmotion ........................