Category Archives: Graduate posts

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Qualifying exams

Qualifying exams

This page contains specific information about each of the four qualifying exams (under the new system):

Algebra exam

The algebra qualifying exam covers several standard topics in abstract algebra.

Material
  1. Group theory: basics of group actions, semidirect products, class equation, Sylow theorems, applications, solvable groups, Jordan–Hölder theorem
  2. Field and Galois theory: finite fields, separable and normal extensions, Fundamental theorem of Galois theory, applications (e.g. solvability by radicals, constructions by straightedge and compass, …), determining Galois groups
  3. Ring theory: factorization in domains, simplicity of matrix algebras
  4. Module theory: basics, projectivity, injectivity, tensor products, flatness, Noetherian property, exact sequences, commutative diagrams, structure theory of modules over a PID, consequences for canonical forms of matrices and other linear algebra
  5. Language of category theory: objects, arrows, Hom, functors, natural transformations, universal objects, products, coproducts, Yoneda lemma
  6. Multilinear algebra: pairings, wedge products, symmetric products, multilinear forms over rings
  7. Basic commutative algebra: local rings and localization, integral extensions, Hilbert Basis Theorem, Noether Normalization, Hilbert’s Nullstellensatz
Textbooks

The following textbooks are recommended:

  • Dummit and Foote, Abstract algebra
  • Lang, Algebra
  • Rotman, Advanced Modern Algebra
  • Hungerford, Algebra
  • Jacobson, Basic Algebra I & II
Sample Exams
Analysis exam

The analysis qualifying exam covers topics in measure theory and real analysis.

Material
  1. Measure theory on Euclidean space: the Borel σ-algebra, construction of Lebesgue measure on finite-dimensional Euclidean spaces.
  2. Functions: continuous functions, uniformly continuous functions, absolutely continuous functions, functions of bounded variation and rectifiable curves, Borel functions, measurable functions, simple functions, the relations between these classes, Lusin’s theorem.
  3. Integration: the Lebesgue integral, Fatou’s lemma, the monotone and dominated convergence theorems, applications to moving limits through integrals, Fubini’s theorem, definition and completeness of Lp spaces, the Lebesgue differentiation theorem.
  4. Convergence of functions: pointwise convergence, the supremum norm and uniform convergence, convergence in measure, convergence in Lp spaces, the relations between these notions, Egorov’s theorem.
  5. Inequalities: Chebyshev, Cauchy–Schwarz, Jensen, Minkowski (sum and integral forms), Hölder.
  6. Density: the Weierstrass theorem and density of polynomials in appropriate Lp spaces, convolution with approximate identities and density of smooth functions in appropriate Lp spaces.
  7. General measure theory: σ-algebras, outer measures, counting measure, product measures, Lp spaces of a general measure space, absolute continuity of measures and the Radon–Nikodym theorem.
Textbooks

The following textbooks are recommended:

  • Folland, Real analysis: Modern techniques and their applications
  • Royden, Real analysis
  • Rudin, Real and complex analysis
  • Stein and Shakarchi, Real analysis: Measure theory, integration, and Hilbert spaces
Sample Exams
Applied mathematics exam

The applied mathematics qualifying exam covers topics in dynamical systems, partial differential equations, and applied linear algebra.

Material
  1. Basic dynamical systems concepts: definition of a dynamical system (continuous and discrete), equilibrium states, ω,α-limit sets, invariant sets, stability of equilibrium states and periodic solutions, population dynamics models; linear systems, stable, unstable, center spaces; non-linear systems and existence/uniqueness of solutions; linearization, topological equivalence/conjugacy, center manifold theory (applications: species competition models, SIR models, predator-prey models); some global nonlinear techniques (nullclines, Lyapunov function, applications: nonlinear pendulum, SIR models); limit cycles. Poincaré–Bendixson theory in $\mathbb R^2$ (applications: Van der Pol oscillator, predator-prey models with limit cycle, oscillating chemical reactions); stability of periodic solutions, Poincaré map.
  2. Bifurcation theory: family of systems, structural stability, definition of a bifurcation; Peixoto’s theorem, Morse–Smale systems; examples of one-parameter bifurcations of equilibrium states (application: laser phenomenon); genericity, transverse intersections, versal unfoldings (deformations) and codimension of a bifurcation (application: spruce budworm model (codimension-2 bifurcation)); the Hopf bifurcation (applications: oscillating chemical reactions, FitzHugh–Nagumo model); center manifold theory (for bifurcations); global bifurcations (homoclinic, heteroclinic).
  3. Introduction to chaos: examples of chaotic behavior (discrete logistic model, Duffing oscillator, Lorenz system, Henon map, Horseshoe map, symbolic dynamics), sensitivity to initial condition; more on logistic model (period doubling, Feigenbaum constant, dense periodic orbits and Sharkovskii’s theorem); strange attractors; Lyapunov exponents.
  4. Elements of partial differential equations: first order linear and quasilinear PDEs and the method of characteristics, second order linear PDEs and their classification, the Sturm–Liouville problem, Green’s functions and fundamental solutions, the Fourier transform, equilibrium solutions of time-dependent PDEs.
  5. Elements of applied linear algebra: eigenvalues, Rayleigh quotients, the Jordan normal form, singular value decomposition, Gram–Schmidt orthogonalization, convergence of finite difference schemes.
Textbooks

The following textbooks are recommended:

  • Perko, Differential equations and dynamical systems
  • Strogatz, Nonlinear dynamics and chaos: with applications to physics, biology, chemistry, and engineering
  • Hirsch, Smale, and Devaney, Differential equations, dynamical systems, and an introduction to chaos
  • Friedberg, Insel, Linear algebra
  • Roman, Advanced Linear algebra
  • Bleeker, Csordas, Basic partial differential equations
  • Evans, Partial differential equations
Sample Exams
Topology exam

The topology qualifying exam covers topics in algebraic topology.

Material
  1. Some point set topological concepts: basic definitions, compactness, separation axiom, connectedness/path-connectedness, retractions, contractibility, quotient topologies.
  2. Homotopy theory: CW complexes, homotopic maps, properties of homotopy in CW complexes, homotopy equivalence, homotopy extension.
  3. Some group theory: free groups, free products, universal properties, presentations of groups.
  4. Brief overview of basic category-theoretic definitions: categories, functors, natural transformations, examples.
  5. The fundamental group: a brief discussion of homotopy groups and their functoriality, long exact sequences of homotopy groups, definition of the fundamental groupoid and the fundamental group, calculation of the fundamental group of a circle, winding numbers, the van Kampen theorem together with examples of fundamental group calculations, K(π, 1) spaces and their properties.
  6. Covering spaces: basic definitions, lifting properties, deck group actions, the Galois correspondence between covers and subgroups of the fundamental group.
  7. Brief overview of (co)homological algebra: (co)chain complexes, (co)chain maps, exact sequences, (co)homology, long exact sequences induced by short exact sequences.
  8. Homology: cellular and singular homology and their equivalence, reduced homology, relative homology, excision, Mayer–Vietoris sequences, the Künneth formula, examples, first homology and the fundamental group, homology with coefficients, definition of cohomology and calculation of examples.
  9. Applications of homology: orientability, degrees of mappings, Lefschetz fixed point theorem, Brouwer fixed point theorem, invariance of domain Borsuk–Ulam theorem.
  10. Structures on cohomology rings: universal coefficients theorem for homology/cohomology, the cup and cap products, calculating cohomology rings, intersection numbers, duality theorems.
Textbooks

The following textbooks are recommended:

  • Bredon, Topology and geometry
  • Hatcher, Algebraic topology
  • Spanier, Algebraic topology
Sample Exams

 

Marriott’s doctoral defense

O1_to_O2
John Marriott, a student of Prof. Monique Chyba, will defend his doctoral dissertation on September 5.

Abstract

This work addresses the contrast problem in nuclear magnetic resonance as a Mayer problem in
optimal control. This is a problem motivated by improving the visible contrast in magnetic resonance
imaging, in which the magnetization of the nuclei of the substances imaged are first prepared by
being set to a particular con figuration by an external magnetic field, the control. In particular we
examine the contrast problem by saturation, wherein the magnetization of the first substance is
set to zero. This system is modeled by a pair of Bloch equations representing the evolution of the
magnetization vectors of the nuclei of two di fferent substances, both influenced by the same control
field.
More…