# Qualifying Exams

Doctoral students must take quals in three of the six available areas: (1) Numerical Analysis/Linear Algebra, (2) Analysis, (3) Algebra, (4) PDEs, (5) Algebraic Topology, and (6) Geometry. Please see the PhD Handbook for more details on the exams.

Examination Dates and Registration: Click below to see dates for upcoming exams and to signup. Students must sign up at least 2 weeks prior to the date of the exam, and may withdraw before that 2 week deadline. Any student who is still signed up by the 2-week mark and does not show for the exam, will receive a No Pass.

Register for the next round of qualifying exams

**Core Examination Topics:** These are the specific topics that may be covered on a given exam.

#### (1) Numerical Analysis/Linear Algebra

Systems of Equations

Linear Systems of Equations:

Gaussian elimination, LU- and Cholesky decompositions for full and sparse matrices, operation counts, stability of linear systems (condition number), stability of Gaussian elimination. Basic iterative methods (Jacobi, Gauss-Seidel, Successive Overrelexation method), Conjugate Gradient MethodEigenvalue Problems

Gerschgorin theorem, power method, inverse power method, stability of eigenvalue problemsNonlinear Systems of Equations, Optimization:

Newton's method, quasi-newton methods, fixed point iteration. Newton and Levenberg-Marquardt methods for unconstrained optimization.Numerical ApproximationInterpolation:

Lagrange and Hermite interpolating polynomials, Runge phenomena. Splines, least squares approximation of functions and orthogonal polynomials.Integration:

Newton-Cotes methods, Gaussian quadrature, Euler-MacLaurin formula, Adaptive quadrature.Differential Equations:

Convergence of explicit one-step methods, Stiffness, A- stability, impossibility of A-stable explicit Runge-Kutta methodsReferences

An Introduction to Numerical Analysisby K. E. Atkinson (Wiley)Unconstrained Optimizationby P. E. Frandsen, K. Jonasson, H. B. Nielsen, and O. TingleffAnalysis of Numerical Methodsby E. Isaacson and H. B. Keller (Wiley, Dover reprint)Finite Difference Methods for Ordinary and Partial Differential Equationsby R. LeVeque (SIAM)A First Course in the Numerical Analysis of Differential Equationsby A. Iserles (Cambridge University Press)

#### (2) Analysis

In addition to the topics covered below, students are expected to be proficient in the topics covered in an undergraduate sequence in Real and Complex Analysis. These are the topics covered in our Math 133, 135, and 136 courses at Tufts.

Metric Spaces:Stone-Weierstrass theorem, Arzela-Ascoli theorem, Baire category theorem.Measure and Integration:General measure spaces (including sigma-algebras, measures, completions), Caratheodory Extension theorem, Borel sets, Lebesgue measure. Cantor set and Cantor function. Measurable functions, abstract integration, Lebesgue integral and limit theorems for integrals. Complex measures, total variation measure, absolutely continuous, singular measures, and Radon-Nikodym theorem. Product measures and Fubini-Tonelli theorem.Functional Analysis:Banach spaces, Lp spaces, the Holder and Minkowski inequalities, the Banach-Steinhaus, Open Mapping, and Hahn-Banach theorems. Hilbert spaces, orthogonal decompositions and projections, orthonormal bases, Fourier series. Dual spaces, operator norms, adjoints, duality of Lp and Lq. Riesz representation theorem.Complex Analysis: Analyticity, Cauchy-Riemann equations, elementary functions, Cauchy's theorem, Cauchy integral formula, Liouville's theorem, Morera's theorem, Taylor expansions, classification of singularities, Laurent expansions, the residue theorem, linear fractional transformations.Suggested References:

Real Analysisby H. L. Royden (Macmillan)Real and Complex Analysisby Walter Rudin (McGraw-Hill)Real Analysis: Measure Theory, Integration, and Hilbert Spacesby E. M. Stein and R. Shakarchi (Princeton University Press)Complex Analysisby E. M. Stein and R. Shakarchi (Princeton University Press)Functional Analysis: Introduction to Further Topics in Analysisby E. M. Stein and R. Shakarchi (Princeton University Press)Fourier Analysis: An Introductionby E. M. Stein and R. Shakarchi (Princeton University Press)

#### (3) Algebra

Generalities:

- Quotients and Isomorphism Theorems for groups, rings, and modules.

Groups:

- The action of a group on a set; applications to conjugacy classes and the class equation.
- The Sylow theorems; simple groups.
- Simplicity of the Alternating Group for n≥5n≥5.

Rings and Modules:

- Polynomial rings, Euclidean domains, principal ideal domains.
- Unique factorization; the Gauss lemma and Eisenstein's criteria for irreducibility.
- Free modules; the tensor product.
- Structure of finitely generated modules over a PID; applications (finitely generated abelian groups, canonical forms of linear transformations).

Fields:

- Algebraic, transcendental, separable, and Galois extensions, splitting fields.
- Finite fields, algebraic closures.
- The fundamental theorem of Galois theory for a finite extension of a field of arbitrary characteristic.

References

Basic Algebra Iby Nathan Jacobson (W. H. Freeman)Algebraby Thomas W. Hungerford (Springer)Algebra (in part)by Serge Lang (Addison-Wesley)Algebraby Michael Artin (Prentice Hall)Abstract Algebraby David S. Dummit and Richard M. Foote (Prentice Hall)

#### (4) Partial Differential Equations

Linear Partial Differential EquationsElliptic PDE:

Laplace, Poisson and Helmholtz equations, boundary-value problems, existence and uniqueness, Fredholm alternative, weak and strong elliptic maximum principles, boundary regularity, Sobolev spaces, weak solutions, Lax-Milgram Theorem, Galerkin method, variational principles, Fréchet derivative.

Parabolic PDE:

Heat equation, Schrödinger equation, existence and uniqueness of solutions, weak and strong parabolic maximum principles, regularity.

Hyperbolic PDE:

Wave equation, method of characteristics.

Spectral Analysis:

Fourier series, Fourier transforms, convergence and approximation properties, generalized functions, distributions. Eigenfunction expansion, Sturm-Liouville Theory, Rayleigh quotient, Rayleigh-Ritz method, Green's functions.

Quasilinear and Nonlinear PDE:

Cauchy-Kovalevskaya theorem, hyperbolic systems, shallow-water equations, gas-dynamic equations, Fourier methods, energy methods. Method of characteristics, weak solutions, jump conditions, entropy conditions.

References

Basic Linear Partial Differential Equationsby F. Treves (Academic Press, Dover reprint)An Introduction to Nonlinear Partial Differential Equationsby J. D. Logan (Wiley)An Introduction to Partial Differential Equationsby Pinchover and RubensteinApplied Function Analysisby GriffelPartial Differential Equationsby L. C. Evans (AMS, Second Edition)

#### (5) Algebraic Topology

Homotopy and Fundamental Group:

- Homotopy and homotopy equivalence.
- Fundamental group - including key examples.
- Van Kampen's Theorem - basic calculations using cell complexes.

Covering Spaces:

- Basic lifting properties.
- Universal covering.
- Relation between coverings and subgroups of the fundamental group.
- Group actions.
- Deck transformations.

Homology:

- Simplicial homology definition and computations.
- Singular homology definition and basic properties.
- Exact Sequences
- Degree
- Mayer-Vietoris

References

Algebraic Topology, by A. Hatcher, Chapters 1 and 2.1, 2.2 (through Mayer-Vietoris)Algebraic Topology, by Greenburg, parts I and II through 17

#### (6) Geometry

Manifolds:

- Key examples of manifolds such as spheres, tori, projective spaces.
- Quotients, submanifolds, regular level sets, Lie groups.
- Smooth maps between manifolds.

Tangent Spaces:

- Differential and rank of a smooth map.
- Regular level set theorem (Implicit function theorem).
- Vector fields, integral curves.
- Lie algebra of a Lie group.

Differential Forms and Integration:

- Wedge product, pullback of forms, exterior derivative.
- Orientation, integral of an n-form, Stokes' theorem.

References

An Introduction to Manifolds (Sections 1-23)by Loring W. Tu (Springer Universitext, 2011).Foundations of Differentiable Manifolds and Lie Groups (Chapters 1-3)by Frank Warner (Springer GTM)