Modular Forms and L-functions
[ambient page updated 15:05, May 17, 2008]
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[ home ]
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[ garrett@math.umn.edu ]
Naturally, various new snippets come into existence before old things
are revised or organized. In reverse chronological order:
- [ Fourier analysis on finite
abelian groups ]
... [ updated 17:10, Oct 17, 2007]
... Decomposition of the regular representation of a finite abelian
group, that is, acting on functions on itself, under
translation. Assumes only spectral theory on finite-dimensional
complex vectorspaces.
Notes (reverse chronological order):
- [14] (DRAFT)
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Dirichlet series from automorphic forms]
... [ updated 17:03, Mar 15, 2006]
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Beginning of study of Dirichlet series with meromorphic continuation
and functional equation obtained from automorphic forms, both
holomorphic ones and waveforms.
- [13] (DRAFT)
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toward waveforms]
... [ updated 16:03, Mar 15, 2006]
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Beginning of study of eigenfunctions for the invariant Laplacian on
the upper half-plane. Introduction of (non-holomorphic) Eisenstein
series, cuspforms.
- [12] (DRAFT)
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Invariant differential operators]
... [ updated 13:03, Mar 15, 2006]
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More instrinsic discussion of differential operators related to group
actions. Introduction of Casimir operator in the
universal enveloping algebra attached to a Lie
algebra, etc. No assumption of prior acquaintance with Lie
algebras or Lie groups.
- [11] (DRAFT)
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Functions on spheres]
... [ updated 15:05, May 17, 2008]
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Harmonic polynomials, Fourier-Laplace series, Sobolev spaces, on
spheres. Duals, distributions (generalized functions).
- [10] (Functions on the line)
- [exercises 10]...
[ updated 13:12, Dec 11, 2005]
... Easy exercises about distributions, Fourier transforms, tempered
distributions
- [09]
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Functions on circles, Fourier series, Sobolev spaces]
... [ updated 10:04, Apr 21, 2006]
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Natural function spaces of k-fold continuously differentiable
functions. Hilbert-space theory of Fourier series. Sobolev's
comparison of natural function spaces with certain Hilbert
spaces. Duals, distributions (generalized functions).
- [08]
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Homogeneous spaces: spheres, projective spaces, n-balls]
... [ updated 13:11, Nov 02, 2006]
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Spheres with rotation groups acting, projective spaces with
projectivized linear actions, translation to linear-fractional
transformations [sic], groups acting transitively on complex n-balls.
- [07] (DRAFT)
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Modular curves, raindrops through kaleidoscopes]
... [ updated 16:02, Feb 24, 2006]
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Modular curves formed as quotients of the upper half-plane. Limits of
quotients by p-power congruence subgroups, action of
SL(2,Zp) and SL(2,Qp),
or GL(2,Zp) and GL(2,Qp) on the upper-and-lower
half-planes. Non-abelian analogue of
solenoids. In a picture, the simplest modular curve looks like a
raindrop, and the projective limit is something seen through a
kaleidoscope. Rudimentary pictures eventually.
- [06]
[Historical origins]
... [ updated 10:02, Feb 27, 2006]
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Bits of history, especially to clarify etymology: integrals for
arc length of ellipses, elliptic integrals, elliptic functions,
lattices/modules, modular forms. (Perhaps the traditional pictures
will be inserted at some later point.)
- [exercises 06]...
[ updated 13:11, Nov 19, 2005]
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Constructions of periodic functions, orbits on projective spaces, some
counting issues, other oddments.
- [05]
[Comparison with
classical presentations of p-adic numbers]
... [ updated 10:11, Nov 14, 2005]
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Hensel's lemma, classical metric definition of p-adic numbers, p-adic
exponential and logarithm (developing formal power series as useful
device), comparison with projective limit definition. Similar
comparison of definitions of adeles.
- [exercises 05]...
[pdf]
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basic classical viewpoint on p-adic numbers
- [exercises 04]...
[ updated 14:10, Oct 30, 2005]
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metrics, completeness, more colimits, more automorphism of solenoids
- [04] [The ur-solenoid and adeles]
... [ updated 11:10, Oct 31, 2005]
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More solenoids, with automorphism groups factoring over primes,
leading to the universal or ur-solenoid, which also introduces the
adeles, as a colimit, much as Qp is a
colimit of p-nZp. Incidental
very general results about limits and products commuting, isomorphism of
cofinal (directed) limits.
- [exercises 03]...
[ updated 14:10, Oct 30, 2005]
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Some topology, some commutation of operators, some galois theory.
- [03] [Bigger diagrams, more
automorphisms, colimits]
... [ updated 10:11, Nov 03, 2005]
...Bigger automorphism groups visible via bigger diagram for
2-solenoid. 2-adic numbers as colimit. Slightly
broader discussion of colimits, strict colimits.
- [exercises 02]...
[ updated 17:10, Oct 03, 2005]
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Further mapping-property exercises.
- [02] [Solenoids]
... [ updated 13:01, Jan 13, 2006]
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Initial fragment of discussion of projective limits
illustrated by solenoids (after Eilenberg). This is the beginning of a
story that will show how p-adic
groups, adele groups, etc. arise naturally as automorphisms of
families of more primitive, simpler objects. Review
of fundamentals regarding topological groups.
- [01] [Review example: product topology]
...
[ updated 12:01, Jan 06, 2006]
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Review example: characterization of objects by (universal) mapping
properties, the product topology. Why is the product topology so coarse?
This course will illustrate how standard modern mathematics helps us
understand complicated phenomena. To do so, we will introduce the
phenomena themselves first in (reconstructed forms of) their genuine
historical settings, and then reconsider them in more contemporary
terms. Part of the point is that modern mathematics helps us do
mathematics better.
More specifically, the zeta functions, L-functions, theta series, and
modular forms that arose and played an important role in number theory
in the 19th century and early 20th (and still do) are more complicated
than many more classical mathematical objects and problems. Thus, it
is not surprising that assimilation of these things into the body of
standard mathematics took many decades. It turns out (as observed by
Gelfand, Selberg, Langlands, and others starting in the 1940s, though
having antecedents in work of Schur, Frobenius, Lie, Killing, Cartan
circa 1890-1910) that spectral decompositions ,
equivalently, representation theory (of several different
genres) can be made to play a decisive role. More colloquially, but
quite literally, this is the exploitation of symmetry. We
will motivate this viewpoint through many examples, develop the basic
techniques, and see how the ideas help us.
And of course many other basic ideas of the last half of the 20th
century are useful, as proof mechanisms, as mnemonic devices, and as
organizational notions. We will see that it is profitable to
expect and look for application of standard ideas
such as naive categorical notions (universal mapping
properties) from Eilenberg-MacLane, and notions about generalized
functions (distributions) from Schwartz and Sobolev. And the
relevance of spectral and representation-theoretic
structures will be seen to be both pervasive and helpful.
We will regularly return to the primitive original forms of classical
questions and see how they can be recast into more intelligible and
answerable forms in terms of standard modern mathematics. I hope this
will show people that they can acquire sufficient technique and
understanding to do new things themselves.
© 1996-2008,
Paul Garrett
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[ garrett@math.umn.edu
]
[this page is http://www.math.umn.edu/%7Egarrett/m/mfms/]
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strictly those of the page author. The contents of this page have not
been reviewed or approved by the University of Minnesota."