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62345-01 - Vorlesung mit Übungen: Qualitative Methods in Theoretical Physics 4 KP

Semester Herbstsemester 2024
Angebotsmuster Jedes Herbstsemester
Dozierende Jelena Klinovaja (jelena.klinovaja@unibas.ch, BeurteilerIn)
Inhalt In physics, particularly in condensed matter, the same mathematical tools proves invaluable for tackling diverse problems. This course aims to demystify some of these tools, often mentioned briefly in other classes but seldom explored in depth. Throughout our sessions, we will learn various techniques for computing complex integrals: whether through exact methods or approximations. Additionally, we will learn to solve transcendental and differential equations exactly or employing perturbation and variational methods. In consequence, we will study various special functions in detail.

Students can choose the topic of the last few classes. Past topics have included the WKB approximation, the Schrieffer-Wolf transformation, the concept of Principal value, and Wick's theorem. Each new concept and method is illustrated through at least one example drawn from the realm of physics, spanning classical Newtonian mechanics, thermodynamics, electromagnetism, wave physics, quantum mechanics, and ultimately, condensed matter.
Lernziele The content of each lecture is subject to changes depending of the pace of the class. The
last lecture(s) will change depending on the wishes of the attendees (to choose the EXTRA in
particular).

Plan:

0. Complex integration
• Residue theorem and application.
• Handling branch cuts.
• Laplace method for differential equations.

1. Transcendental equations
• Graphical methods (determining special points).
• Iteration method.
• Asymptotics around special points.
• Examples: magnetization of ferromagnetic (mean-field theory), energy levels of a finite
(square) quantum well.

2. Integrals with small parameters
• Expansion of the integrand into series.
• Determining the intervals of integration giving the main contribution (and expanding the
integrand there).
• Estimating sums of series using integrals.

3. Method of steepest descent (for integrals and series)
• Basic method and conditions.
• Beta, Gamma, and Airy function; Stirling formula.
• Estimating sums of series with the method.

4. Integrals with parameters and integral representations
• Gauss integral and Gamma-function of half-integer argument.
• Integral representation of a logarithm.
• Integrals of exponential and trigonometric functions.
• Integral of the Bessel function.

5. Integrals of rapidly varying functions and asymptotical expansion.
• Integration of function with exponential damping.
• Method of the stationary phase.
• More on the Airy and the Bessel function.

6. Differential equations with small parameters
• Green’s function.
• Perturbation theory.
• Perturbation theory in the presence of resonances.

7. Variational method
• General method, notion of action.
• Example: geometric optics and classical mechanics.

8. More on special functions
(may be skipped on popular demand)
• Dirac deltas.
• Airy function.
• Bessel function.
• Hermite polynomial.

The following lectures may vary depending of suggestions of the students and the pace of the
lectures.

EXTRA 1. Introduction to WKB
• Introduction to the method.
• Bohr-Sommerfeld quantization rule.
• Double-well potential.
• Quasiclassical tunneling under a barrier.

EXTRA 2. The Shrieffer-Wolf transformation
• Core concepts and generalization
• Derivation of the t − J model

EXTRA 3. More integral representations
• Fourier transform of Coulomb potential.
• Hubbard-Stratonovich transformation.

EXTRA 4. Generalization of WKB to low-lying energy states
(only if extra 1 done)
• Reminder.
• Splitting in double-well potential.

EXTRA 5. Zoo of generalization
• Multiple integrals.
• Saddle-point approximation generalizations.

Otherwise, these themes are also possible:
Possible extensions:
• Some aspects of probability theory.
• Order of magnitudes estimations.
• Other suggestions

 

Unterrichtssprache Englisch
Einsatz digitaler Medien kein spezifischer Einsatz

 

Intervall Wochentag Zeit Raum
wöchentlich Dienstag 10.15-12.00 Physik, Sitzungszimmer 1.09
wöchentlich Mittwoch 10.15-12.00 Physik, Seminarzimmer 4.1

Einzeltermine

Datum Zeit Raum
Dienstag 17.09.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 18.09.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 24.09.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 25.09.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 01.10.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 02.10.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 08.10.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 09.10.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 15.10.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 16.10.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 22.10.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 23.10.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 29.10.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 30.10.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 05.11.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 06.11.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 12.11.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 13.11.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 19.11.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 20.11.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 26.11.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 27.11.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 03.12.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 04.12.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 10.12.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 11.12.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Dienstag 17.12.2024 10.15-12.00 Uhr Physik, Sitzungszimmer 1.09
Mittwoch 18.12.2024 10.15-12.00 Uhr Physik, Seminarzimmer 4.1
Module Modul: Vertiefung Physik (Masterstudium: Nanowissenschaften)
Modul: Vertiefungsfach (Masterstudium: Physik)
Leistungsüberprüfung Lehrveranst.-begleitend
An-/Abmeldung zur Leistungsüberprüfung Anm.: Belegen Lehrveranstaltung; Abm.: stornieren
Wiederholungsprüfung keine Wiederholungsprüfung
Skala 1-6 0,5
Wiederholtes Belegen beliebig wiederholbar
Zuständige Fakultät Philosophisch-Naturwissenschaftliche Fakultät, studiendekanat-philnat@unibas.ch
Anbietende Organisationseinheit Departement Physik

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