DOCSLIB.ORG

Chapter 2: Time-Independent Perturbation Theory

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 2: Time-Independent Perturbation Theory 4 Phys460.nb 2 Time-Independent Perturbation Theory 2.1. Overview 2.1.1. General question Assuming that we have a Hamiltonian, H=H 0 +λH 1 (2.1) where λ is a very small real number. The eigenstates of the Hamiltonian should not be very different from the eigenstates of H 0. If we already know all eigenstates of H0, can we get eigenstates of H 1 approximately? Bottom line: we are studying an approximate method. 2.1.2. Why perturbation theory? Why we need to study this approximation methods? (considering the fact that numerical methods can compute the eigenstates very efficiently and accurately for any Hamiltonian that we consider in this course) Reason number I: It is part of the history (QM was born before electronic computer becomes a powerful tool in scientific research). Reason number II: It reveals to us universal principles, which are very important and cannot be obtained from just numerical simulations Reason number III: The idea of perturbation theory has very deep and broad impact in many branches of physics. Perturbation theories is in many cases the only theoretical technique that we have to handle various complex systems (quantum and classical). Examples: in quantum field theory (which is in fact a nonlinear generalization of QM), most of the efforts is to develop new ways to do perturbation theory (Loop expansions, 1/N expansions, 4-ϵ expansions). 2.1.3. Assumptions Assumption #1: we know all eigenstates of H 0, as well as their corresponding eigenenergies 0 0 0 0 H ψn =E n ψn (2.2) Assumption #2: we know the perturbation H '. What do we mean by knowing H '? Here, we mean that we can write down H ' using the 0 0 0 complete basis of ψn , i.e., we know the value of ψn H' ψm for any m and n. Assumption #3: we only consider quantum states with discrete eigenenergies In general, the energy spectrum of a quantum system (i.e. all eigenvalues of the Hamiltonian) falls into one of the following three general possibilities ◼ A discrete spectrum: eigenenergies can only take certain discredited values (example: infinite deep potential wells, e.g. harmonic potential En = (n+1/2) ℏω) Phys460.nb 5 ◼ A continuous spectrum: eigenenergies can take any (real) values in certain allowed range (example: a constant potential. Here, any E≥V is an eigenenergy) ◼ A mixed spectrum: some parts of the spectrum are continuous, while other parts has discrete eigenenergies. (example: a finite potential well. Here, we may have some discrete states inside the well. But for E above the top of the potential well, we have a continuous spectrum). Q: Consider the energy spectrum of an attractive Coulomb (1/r) potential. Is it discrete, continuous or mixed? A: It is mixed. When we consider the an attractive Coulomb potential, we mostly focus on the negative energy states (E<0). This part of the spectrum is discrete, as we all know very well from the study of a hydrogen atom. But if we look at states with positive energies, there is a continuous spectrum for E> 0. For E> 0, the system is NOT a bound state, i.e. the proton and the electron doesn’t form an atom. In other words, we have a high probability found the proton and the electron to be separated far from each other. There, the attractive potential is very small and negligible, so we have two free particles and only need to consider their kinetic energies. For free particles, we know that any positive energy is an allowed eigenenergy (i.e. we have a continuum spectrum for E> 0). Bottom line: in this chapter, our perturbation theory only consider discrete spectrum or the discrete part of a mixed spectrum. Another version of assumption #3: we only consider confined states. (In QM, in most cases, confined states=discrete energy and unconfined states=continuous energy). Comment: In QM, we only study discrete states in a perturbation theory. But this is NOT true for other branches of physics. For example, in quantum field theory, perturbation theory is applied to continuous spectral. 2.2. Non-degenerate Perturbation Theory 2.2.1. Assumptions 0 0 0 1 Key assumption: we consider a specific state ψn . Here, we assume that En -E m is much larger than λH for any other 0 eigenstate ψm 2.2.2. Preparation #1 wavefunctions 0 Since the eigenstates of H0 form a compete basis, we can write down any quantum state as a linear superposition of ψm 0 ψ〉= am ψm m (2.3) Now, if we consider an eigenstate of H, ψn, it can also be written in a similar fashion 0 ψn= am ψm m (2.4) 0 As discussion above, if λ is small, an eigenstate of H would be similar to an eigenstate of H0. Here, we assume that ψn is very close to ψn . 0 This means that an ≈ 1 and for other values of m≠n, a m ~0, To highlight this, we separate the term for ψn out from the sum 0 0 ψn=a n ψn + am ψm m≠n (2.5) It turns out that it is usually more convenient to use unnormalized eigenstates. Now, let us define unnormalized eigenstates of H 1 am 0 0 ψn〉= ψn= ψn + ψm m≠n (2.6) an an For simplicity, we will now call am /a n =c m 0 0 ψn〉= ψn + cn ψm m≠n (2.7) Because am ~ 0 and an ~ 1, we know that cm ~0 for small λ. Comment #1: This state is NOT normalized 2 〈ψn ψn〉=1+ cm ≥1 m≠n (2.8) 6 Phys460.nb But we can easily normalized it, if we want to 1 ψ = ψn n (2.9) 2 1+ ∑m≠n cm 0 Comment #2: (almost) any quantum states can be written in the form of Eq. (2.3). This is because ψm forms a complete basis. Q: what does the word “almost” mean here? 0 A: If a state is orthogonal to ψn , we cannot write the state the form of Eq. (2.3). But we don’t need to worry about it here, because we are 0 doing perturbation theory and we know that the eigenstates of H is close to eigenstates of H 0. So it can not be orthogonal to ψn . Bottom line: we are not making any assumptions or approximations here. It is just a new way to write down eigenstates of H. Comment #3: cms are functions of λ, i.e. cm(λ). For small λ, we can use the Taylor series: (1) (2) 2 (3) 3 cm =c m λ+c m λ +c m λ + … (2.10) 0 Here, the Taylor series doesn’t contain the 0th order term of λ (i.e. the constant term). This is because when λ= 0, ψn〉= ψn , and thus cm(λ) = 0 at λ= 0. As a result, 0 0 0 ∞ (k) k 0 0 ∞ k (k) 0 ψn〉= ψn + cm(λ) ψm = ψn + cm λ ψm = ψn + λ cm ψm m≠n m≠n k=1 k=1 m≠n (2.11) If we define k (k) 0 ψn = cm ψm m≠n (2.12) we get 0 1 2 2 ψn〉= ψn +λ ψn +λ ψn +… (2.13) This is Eq. [6.5] in the textbook. 1 2 0 0 Important: ψn , ψn … doesn’t contain ψn . In other words, all corrections are orthogonal to ψn . 2.2.3. Preparation #2 eigenenergies Eigenenergies of H are also functions of λ, and for small λ, we can use the Taylor series: 0 1 2 2 En(λ) =E n +λE n +λ En + … (2.14) This is Eq. [6.6] in the textbook. 2.2.4. Schrodinger Equation in the perturbation theory H ψn〉=E n ψn〉 (2.15) 0 1 2 2 0 1 2 2 0 1 2 2 (H0 +λH') ψn +λ ψn +λ ψn +…=E n +λE n +λ En + … ψn +λ ψn +λ ψn +… (2.16) 0 1 0 2 2 1 0 0 0 1 1 0 2 0 2 1 H0 ψn + λH 0 ψn +H' ψn +λ H0 ψn +H' ψn +…=E n ψn + λE n ψn +E n ψn +λ En ψn +E n (2.17) 1 2 0 ψn +E n ψn +… 1 2 In the perturbation theory, we need to compute two sets of quantities (1) energy corrections at each order En , En ,... and (2) wavefunc- 1 2 3 tion corrections at each order, ψn , ψn , ψn . It turns out that these two set of quantities are entangled together and we need to compute both of them. At each order, we will first compute energy corrections, and then the wavefunction corrections. 2.2.5. Zeroth order The leading order terms in the equation is λ0 = constant 0 0 0 H0 ψn =E n ψn (2.18) Phys460.nb 7 This is identical to the case of λ= 0, i.e. the unperturbed system. 2.2.6. First order To the order of λ, we have 1 0 0 1 1 0 H0 ψn +H' ψn =E n ψn +E n ψn (2.19) 1 0 Here, we first compute the energy correction En . This is done by multiplying on both sides ψn 0 1 0 0 0 0 1 0 1 0 ψn H0 ψn + ψ n H' ψn = ψ n En ψn + ψ n En ψn (2.20) For the first term on the l.h.s., we use the fact that 0 0 0 ψn H0 = ψn En (2.21) 1 0 1 0 1 0 0 1 For the last term on the r.h.s., we use the fact that En is a number (not a quantum operator), and thus ψn En ψn =E n ψn ψn =E n 0 0 1 0 0 0 0 1 1 ψn En ψn + ψ n H' ψn = ψ n En ψn +E n (2.22) 0 0 1 ψn H' ψn =E n (2.23) The first order correction in energy is the expectation value of H '.
Load more

Recommended publications
  • Notes on Statistical Field Theory
    Lecture Notes on Statistical Field Theory Kevin Zhou [email protected] These notes cover statistical field theory and the renormalization group. The primary sources were: • Kardar, Statistical Physics of Fields. A concise and logically tight presentation of the subject, with good problems. Possibly a bit too terse unless paired with the 8.334 video lectures. • David Tong's Statistical Field Theory lecture notes. A readable, easygoing introduction covering the core material of Kardar's book, written to seamlessly pair with a standard course in quantum field theory. • Goldenfeld, Lectures on Phase Transitions and the Renormalization Group. Covers similar material to Kardar's book with a conversational tone, focusing on the conceptual basis for phase transitions and motivation for the renormalization group. The notes are structured around the MIT course based on Kardar's textbook, and were revised to include material from Part III Statistical Field Theory as lectured in 2017. Sections containing this additional material are marked with stars. The most recent version is here; please report any errors found to [email protected]. 2 Contents Contents 1 Introduction 3 1.1 Phonons...........................................3 1.2 Phase Transitions......................................6 1.3 Critical Behavior......................................8 2 Landau Theory 12 2.1 Landau{Ginzburg Hamiltonian.............................. 12 2.2 Mean Field Theory..................................... 13 2.3 Symmetry Breaking.................................... 16 3 Fluctuations 19 3.1 Scattering and Fluctuations................................ 19 3.2 Position Space Fluctuations................................ 20 3.3 Saddle Point Fluctuations................................. 23 3.4 ∗ Path Integral Methods.................................. 24 4 The Scaling Hypothesis 29 4.1 The Homogeneity Assumption............................... 29 4.2 Correlation Lengths.................................... 30 4.3 Renormalization Group (Conceptual)..........................
    [Show full text]
  • Effective Field Theories, Reductionism and Scientific Explanation Stephan
    To appear in: Studies in History and Philosophy of Modern Physics Effective Field Theories, Reductionism and Scientific Explanation Stephan Hartmann∗ Abstract Effective field theories have been a very popular tool in quantum physics for almost two decades. And there are good reasons for this. I will argue that effec- tive field theories share many of the advantages of both fundamental theories and phenomenological models, while avoiding their respective shortcomings. They are, for example, flexible enough to cover a wide range of phenomena, and concrete enough to provide a detailed story of the specific mechanisms at work at a given energy scale. So will all of physics eventually converge on effective field theories? This paper argues that good scientific research can be characterised by a fruitful interaction between fundamental theories, phenomenological models and effective field theories. All of them have their appropriate functions in the research process, and all of them are indispens- able. They complement each other and hang together in a coherent way which I shall characterise in some detail. To illustrate all this I will present a case study from nuclear and particle physics. The resulting view about scientific theorising is inherently pluralistic, and has implications for the debates about reductionism and scientific explanation. Keywords: Effective Field Theory; Quantum Field Theory; Renormalisation; Reductionism; Explanation; Pluralism. ∗Center for Philosophy of Science, University of Pittsburgh, 817 Cathedral of Learning, Pitts- burgh, PA 15260, USA (e-mail: [email protected]) (correspondence address); and Sektion Physik, Universit¨at M¨unchen, Theresienstr. 37, 80333 M¨unchen, Germany. 1 1 Introduction There is little doubt that effective field theories are nowadays a very popular tool in quantum physics.
    [Show full text]
  • Hamiltonian Perturbation Theory on a Lie Algebra. Application to a Non-Autonomous Symmetric Top
    Hamiltonian Perturbation Theory on a Lie Algebra. Application to a non-autonomous Symmetric Top. Lorenzo Valvo∗ Michel Vittot Dipartimeno di Matematica Centre de Physique Théorique Università degli Studi di Roma “Tor Vergata” Aix-Marseille Université & CNRS Via della Ricerca Scientifica 1 163 Avenue de Luminy 00133 Roma, Italy 13288 Marseille Cedex 9, France January 6, 2021 Abstract We propose a perturbation algorithm for Hamiltonian systems on a Lie algebra V, so that it can be applied to non-canonical Hamiltonian systems. Given a Hamil- tonian system that preserves a subalgebra B of V, when we add a perturbation the subalgebra B will no longer be preserved. We show how to transform the perturbed dynamical system to preserve B up to terms quadratic in the perturbation. We apply this method to study the dynamics of a non-autonomous symmetric Rigid Body. In this example our algebraic transform plays the role of Iterative Lemma in the proof of a KAM-like statement. A dynamical system on some set V is a flow: a one-parameter group of mappings associating to a given element F 2 V (the initial condition) another element F (t) 2 V, for any value of the parameter t. A flow on V is determined by a linear mapping H from V to itself. However, the flow can be rarely computed explicitly. In perturbation theory we aim at computing the flow of H + V, where the flow of H is known, and V is another linear mapping from V to itself. In physics, the set V is often a Lie algebra: for instance in classical mechanics [4], fluid dynamics and plasma physics [20], quantum mechanics [24], kinetic theory [18], special and general relativity [17].
    [Show full text]
  • 1 Introduction 2 Classical Perturbation Theory
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server Classical and Quantum Perturbation Theory for two Non–Resonant Oscillators with Quartic Interaction Luca Salasnich Dipartimento di Matematica Pura ed Applicata, Universit`a di Padova, Via Belzoni 7, I–35131 Padova, Italy Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Via Marzolo 8, I–35131 Padova, Italy Istituto Nazionale per la Fisica della Materia, Unit`a di Milano, Via Celoria 16, I–20133 Milano, Italy Abstract. We study the classical and quantum perturbation theory for two non–resonant oscillators coupled by a nonlinear quartic interaction. In particular we analyze the question of quantum corrections to the torus quantization of the classical perturbation theory (semiclassical mechanics). We obtain up to the second order of perturbation theory an explicit analytical formula for the quantum energy levels, which is the semiclassical one plus quantum corrections. We compare the ”exact” quantum levels obtained numerically to the semiclassical levels studying also the effects of quantum corrections. Key words: Classical Perturbation Theory; Quantum Mechanics; General Mechanics 1 Introduction Nowadays there is considerable renewed interest in the transition from classical mechanics to quantum mechanics, a powerful motivation behind that being the problem of the so–called quantum chaos [1–3]. An important aspect is represented by the semiclassical quantization formula of the (regular) energy levels for quasi–integrable systems [4–6], the so–called torus quantization, initiated by Einstein [7] and completed by Maslov [8]. It has been recently shown [9,10] that, for perturbed non–resonant harmonic oscillators, the algorithm of classical perturbation theory can be used to formulate the quantum mechanical perturbation theory as the semiclassically quantized classical perturbation theory equipped with the quantum corrections in powers of ¯h ”correcting” the classical Hamiltonian that appears in the classical algorithm.
    [Show full text]
  • Perturbation Theory and Exact Solutions
    PERTURBATION THEORY AND EXACT SOLUTIONS by J J. LODDER R|nhtdnn Report 76~96 DISSIPATIVE MOTION PERTURBATION THEORY AND EXACT SOLUTIONS J J. LODOER ASSOCIATIE EURATOM-FOM Jun»»76 FOM-INST1TUUT VOOR PLASMAFYSICA RUNHUIZEN - JUTPHAAS - NEDERLAND DISSIPATIVE MOTION PERTURBATION THEORY AND EXACT SOLUTIONS by JJ LODDER R^nhuizen Report 76-95 Thisworkwat performed at part of th«r«Mvchprogmmncof thcHMCiattofiafrccmentof EnratoniOTd th« Stichting voor FundtmenteelOiutereoek der Matctk" (FOM) wtihnnmcWMppoft from the Nederhmdie Organiutic voor Zuiver Wetemchap- pcigk Onderzoek (ZWO) and Evntom It it abo pabHtfMd w a the* of Ac Univenrty of Utrecht CONTENTS page SUMMARY iii I. INTRODUCTION 1 II. GENERALIZED FUNCTIONS DEFINED ON DISCONTINUOUS TEST FUNC­ TIONS AND THEIR FOURIER, LAPLACE, AND HILBERT TRANSFORMS 1. Introduction 4 2. Discontinuous test functions 5 3. Differentiation 7 4. Powers of x. The partie finie 10 5. Fourier transforms 16 6. Laplace transforms 20 7. Hubert transforms 20 8. Dispersion relations 21 III. PERTURBATION THEORY 1. Introduction 24 2. Arbitrary potential, momentum coupling 24 3. Dissipative equation of motion 31 4. Expectation values 32 5. Matrix elements, transition probabilities 33 6. Harmonic oscillator 36 7. Classical mechanics and quantum corrections 36 8. Discussion of the Pu strength function 38 IV. EXACTLY SOLVABLE MODELS FOR DISSIPATIVE MOTION 1. Introduction 40 2. General quadratic Kami1tonians 41 3. Differential equations 46 4. Classical mechanics and quantum corrections 49 5. Equation of motion for observables 51 V. SPECIAL QUADRATIC HAMILTONIANS 1. Introduction 53 2. Hamiltcnians with coordinate coupling 53 3. Double coordinate coupled Hamiltonians 62 4. Symmetric Hamiltonians 63 i page VI. DISCUSSION 1. Introduction 66 ?.
    [Show full text]
  • Conformal Invariance and Quantum Integrability of Sigma Models on Symmetric Superspaces
    Physics Letters B 648 (2007) 254–261 www.elsevier.com/locate/physletb Conformal invariance and quantum integrability of sigma models on symmetric superspaces A. Babichenko a,b a Racah Institute of Physics, the Hebrew University, Jerusalem 91904, Israel b Department of Particle Physics, Weizmann Institute of Science, Rehovot 76100, Israel Received 7 December 2006; accepted 2 March 2007 Available online 7 March 2007 Editor: L. Alvarez-Gaumé Abstract We consider two dimensional nonlinear sigma models on few symmetric superspaces, which are supergroup manifolds of coset type. For those spaces where one loop beta function vanishes, two loop beta function is calculated and is shown to be zero. Vanishing of beta function in all orders of perturbation theory is shown for the principal chiral models on group supermanifolds with zero Killing form. Sigma models on symmetric (super) spaces on supergroup manifold G/H are known to be classically integrable. We investigate a possibility to extend an argument of absence of quantum anomalies in nonlocal current conservation from nonsuper case to the case of supergroup manifolds which are asymptotically free in one loop. © 2007 Elsevier B.V. All rights reserved. 1. Introduction super coset PSU(2, 2|4)/SO(1, 4) × SO(5). Hyperactivity in at- tempts to exploit integrability and methods of Bethe ansatz as a Two dimensional (2d) nonlinear sigma models (NLSM) on calculational tool in checks of ADS/CFT correspondence (see, supermanifolds, with and without WZ term, seemed to be ex- e.g., reviews [12] and references therein), also supports this in- otic objects, when they appeared in condensed matter physics terest, since both spin chains (on the gauge theory side) and 2d twenty years ago as an elegant calculational tool in problems NLSM (on the ADS side) appearing there, usually have a su- of self avoiding walks [1] and disordered metals [2].
    [Show full text]
  • Perturbation Theory in Celestial Mechanics
    Perturbation Theory in Celestial Mechanics Alessandra Celletti Dipartimento di Matematica Universit`adi Roma Tor Vergata Via della Ricerca Scientifica 1, I-00133 Roma (Italy) ([email protected]) December 8, 2007 Contents 1 Glossary 2 2 Definition 2 3 Introduction 2 4 Classical perturbation theory 4 4.1 The classical theory . 4 4.2 The precession of the perihelion of Mercury . 6 4.2.1 Delaunay action–angle variables . 6 4.2.2 The restricted, planar, circular, three–body problem . 7 4.2.3 Expansion of the perturbing function . 7 4.2.4 Computation of the precession of the perihelion . 8 5 Resonant perturbation theory 9 5.1 The resonant theory . 9 5.2 Three–body resonance . 10 5.3 Degenerate perturbation theory . 11 5.4 The precession of the equinoxes . 12 6 Invariant tori 14 6.1 Invariant KAM surfaces . 14 6.2 Rotational tori for the spin–orbit problem . 15 6.3 Librational tori for the spin–orbit problem . 16 6.4 Rotational tori for the restricted three–body problem . 17 6.5 Planetary problem . 18 7 Periodic orbits 18 7.1 Construction of periodic orbits . 18 7.2 The libration in longitude of the Moon . 20 1 8 Future directions 20 9 Bibliography 21 9.1 Books and Reviews . 21 9.2 Primary Literature . 22 1 Glossary KAM theory: it provides the persistence of quasi–periodic motions under a small perturbation of an integrable system. KAM theory can be applied under quite general assumptions, i.e. a non– degeneracy of the integrable system and a diophantine condition of the frequency of motion.
    [Show full text]
  • On the Spectrum of PP-Wave Matrix Theory
    Preprint typeset in JHEP style - HYPER VERSION hep-th/0207034 AEI-2002-047 On the Spectrum of PP-Wave Matrix Theory Nakwoo Kim and Jan Plefka Max-Planck-Institut f¨ur Gravitationsphysik Albert-Einstein-Institut Am M¨uhlenberg 1, D-14476 Golm, Germany kim,[email protected] Abstract: We study the spectrum of the recently proposed matrix model of DLCQ M-theory in a parallel plane (pp)-wave background. In contrast to matrix theory in a flat background this model contains mass terms, which lift the flat directions of the potential and renders its spectrum discrete. The supersymmetry algebra of the model groups the energy eigenstates into supermultiplets, whose members differ by fixed amounts of energy in great similarity to the representation of supersymmetry in AdS spaces. There is a unique and exact zero-energy groundstate along with a multitude of long and short multiplets of excited states. For large masses the arXiv:hep-th/0207034v3 10 Jul 2002 quantum mechanical model may be treated perturbatively and we study the leading order energy shifts of the first excited states up to level two. Most interestingly we uncover a protected short multiplet at level two, whose energies do not receive perturbative corrections. Moreover, we conjecture the existence of an infinite series of similar protected multiplets in the pp-wave matrix model. Contents 1. Introduction 1 2. The Model and its Quantization 2 3. Supersymmetry Algebra and Structure of the Spectrum 4 4. The Perturbative Energy Spectrum and Protected States 8 5. Conclusions and Outlook 12 A. The Supersymmetry Algebra 13 B.
    [Show full text]
  • Normalization of the Ground State of the Supersymmetric Harmonic
    Letters in High Energy Physics LHEP xx, xxx, 2018 Normalization of the Ground State of the Supersymmetric Harmonic Oscillator Ahmed Ayad School of Physics, University of the Witwatersrand, Private Bag 3, WITS-2050, Johannesburg, South Africa Abstract Supersymmetry plays a main role in all current thinking about superstring theory. Indeed, many remark- able properties of string theory have been explained using supersymmetry as a tool. So far, there has been no unbroken supersymmetry observed in nature, and if nature is described by supersymmetry, it must be broken. Supersymmetry may be broken spontaneously at any order of perturbation theory or dynamically due to nonperturbative effects. To examine the methods of supersymmetry breaking, special attention is given to discuss the normalization of the ground state of the supersymmetric harmonic oscillator. This study explains that perturbation theory gives incorrect results for both the ground-state wave function and the energy spectrum and it fails to give an explanation to the supersymmetry breaking. Keywords: supersymmetry breaking, perturbation theory, fermionic as well as bosonic fields using the usual quantum nonperturbative effects mechanical operators method. Then, we consider supersym- metric classical mechanics and study generalized classical Pois- son brackets to Dirac brackets and quantization rules in or- 1. INTRODUCTION der to introduce the superalgebra. Furthermore, the formal- ism of supersymmetry in quantum mechanics is introduced. Supersymmetry, often abbreviated SUSY, was first introduced Subsequently, we give a general background in the concepts in 1971 by Gelfand and Likhtman, Raymond, and Neveu and and methods of supersymmetric quantum mechanics. This fol- Schwartz, and later, it was rediscovered by other groups [1, 2].
    [Show full text]
  • Combinatorial Algorithms for Perturbation Theory and Application on Quantum Computing Yudong Cao Purdue University
    Purdue University Purdue e-Pubs Open Access Dissertations Theses and Dissertations 12-2016 Combinatorial algorithms for perturbation theory and application on quantum computing Yudong Cao Purdue University Follow this and additional works at: https://docs.lib.purdue.edu/open_access_dissertations Part of the Computer Sciences Commons, and the Quantum Physics Commons Recommended Citation Cao, Yudong, "Combinatorial algorithms for perturbation theory and application on quantum computing" (2016). Open Access Dissertations. 908. https://docs.lib.purdue.edu/open_access_dissertations/908 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Graduate School Form 30 Updated PURDUE UNIVERSITY GRADUATE SCHOOL Thesis/Dissertation Acceptance This is to certify that the thesis/dissertation prepared By Yudong Cao Entitled Combinatorial Algorithms for Perturbation Theory and Application on Quantum Computing For the degree of Doctor of Philosophy Is approved by the final examining committee: Sabre Kais Chair Mikhail Atallah Co-chair David Gleich Ahmed Sameh Samuel Wagstaff To the best of my knowledge and as understood by the student in the Thesis/Dissertation Agreement, Publication Delay, and Certification Disclaimer (Graduate School Form 32), this thesis/dissertation adheres to the provisions of Purdue University’s “Policy of Integrity in Research” and the use of copyright material. Approved by Major Professor(s): Sabre Kais Approved by: William
    [Show full text]
  • Hamiltonian Perturbation Theory (And Transition to Chaos) H 4515 H
    Hamiltonian Perturbation Theory (and Transition to Chaos) H 4515 H Hamiltonian Perturbation Theory dle third from a closed interval) designates topological spaces that locally have the structure Rn Cantor dust (and Transition to Chaos) for some n 2 N. Cantor families are parametrized by HENK W. BROER1,HEINZ HANSSMANN2 such Cantor sets. On the real line R one can define 1 Instituut voor Wiskunde en Informatica, Cantor dust of positive measure by excluding around Rijksuniversiteit Groningen, Groningen, each rational number p/q an interval of size The Netherlands 2 2 Mathematisch Instituut, Universiteit Utrecht, ;>0 ;>2 : q Utrecht, The Netherlands Similar Diophantine conditions define Cantor sets Article Outline in Rn. Since these Cantor sets have positive measure their Hausdorff dimension is n.Wheretheunper- Glossary turbed system is stratified according to the co-dimen- Definition of the Subject sion of occurring (bifurcating) tori, this leads to a Can- Introduction tor stratification. One Degree of Freedom Chaos An evolution of a dynamical system is chaotic if its Perturbations of Periodic Orbits future is badly predictable from its past. Examples of Invariant Curves of Planar Diffeomorphisms non-chaotic evolutions are periodic or multi-periodic. KAM Theory: An Overview A system is called chaotic when many of its evolutions Splitting of Separatrices are. One criterion for chaoticity is the fact that one of Transition to Chaos and Turbulence the Lyapunov exponents is positive. Future Directions Diophantine condition, Diophantine frequency vector Bibliography A frequency vector ! 2 Rn is called Diophantine if there are constants >0and>n 1with Glossary jhk;!ij for all k 2 Znnf0g : Bifurcation In parametrized dynamical systems a bifur- jkj cation occurs when a qualitative change is invoked by a change of parameters.
    [Show full text]
  • Statistical Field Theory University of Cambridge Part III Mathematical Tripos
    Preprint typeset in JHEP style - HYPER VERSION Michaelmas Term, 2017 Statistical Field Theory University of Cambridge Part III Mathematical Tripos David Tong Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 OBA, UK http://www.damtp.cam.ac.uk/user/tong/sft.html [email protected] { 1 { Recommended Books and Resources There are a large number of books which cover the material in these lectures, although often from very different perspectives. They have titles like \Critical Phenomena", \Phase Transitions", \Renormalisation Group" or, less helpfully, \Advanced Statistical Mechanics". Here are some that I particularly like • Nigel Goldenfeld, Phase Transitions and the Renormalization Group A great book, covering the basic material that we'll need and delving deeper in places. • Mehran Kardar, Statistical Physics of Fields The second of two volumes on statistical mechanics. It cuts a concise path through the subject, at the expense of being a little telegraphic in places. It is based on lecture notes which you can find on the web; a link is given on the course website. • John Cardy, Scaling and Renormalisation in Statistical Physics A beautiful little book from one of the masters of conformal field theory. It covers the material from a slightly different perspective than these lectures, with more focus on renormalisation in real space. • Chaikin and Lubensky, Principles of Condensed Matter Physics • Shankar, Quantum Field Theory and Condensed Matter Both of these are more all-round condensed matter books, but with substantial sections on critical phenomena and the renormalisation group. Chaikin and Lubensky is more traditional, and packed full of content.
    [Show full text]