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Links in green
are from conference proceedings.
Please contact me
for a copy of any paper you cannot
- Strong local-global
phenomena for Galois and automorphic representations
Preprint for RIMS Conference Proceedings (Kôkyûroku series)
An exposition of Strong Multiplicity One type results and refinements,
with an aim to explain the results of my Contemp. Math.
paper with Ramakrishnan.
A comparison of automorphic and
Artin L-series of GL(2)-type agreeing at degree one primes,
with Dinakar Ramakrishnan
Contemporary Mathematics, to appear (volume in honor of Jim Cogdell)
We show that if a 2-d Artin representation corresponds to an automorphic
representation outside of a density 0 infinite set of places of a certain
form, then they correspond everywhere.
Distinguishing graphs with zeta functions
and generalized spectra,
with Christina Durfee
Linear Algebra and its Applications 481 (2015), 54-82
A fundamental problem in graph theory is: when is a graph determined by its
spectrum? We investigate analogues of this question with zeta functions
in place of spectrum. Our work suggests that zeta functions are more
distinguishing graphs than the usual types of spectra studied.
Test vectors and central L-values for GL(2),
with Daniel File and Ameya Pitale
We extend work of Gross and Prasad on test vectors for GL(2) to cases of joint
ramification, and use this to generalize the L-value formula of my
IMRN paper with Whitehouse, an average-value formula of
Feigon-Whitehouse, and a nonvanishing mod p result of
Periods and nonvanishing of central L-values for GL(2n),
with Brooke Feigon and David Whitehouse
Submitted. (Revised: Apr 16, 2014)
Under some local hypotheses, we prove a relation between the nonvanishing
of twisted central L-values for GL(2n) and periods over
GL(n, E), where E is a quadratic extension.
We also deduce analogous local results for supercuspidal representations.
How often should you clean your room?
with Krishnan (Ravi) Shankar
Discrete Mathematics & Theoretical Computer Science, to
appear (Revised: May 11, 2015)
We introduce and study a combinatorial optimization problem motivated by
the question, "How often should you clean your room?"
Local root numbers, Bessel models, and a conjecture of Guo and Jacquet,
with Masaaki Furusawa
Journal of Number Theory, Special Issue in Honor of
(2015), pp. 150-170.
We make a conjecture about the transfer of global SO(2)-Bessel periods on
SO(2n+1) to GL(n, E) periods on GL(2n), where
E is the quadratic extension associated to the relevant form of SO(2),
and prove this when n = 2.
On central critical values of the degree four L-functions for GSp(4):
a simple trace formula,
with Masaaki Furusawa
Mathematische Zeitschrift, Vol 277, No. 1 (2014), pp. 149-180.
As an application of the Fundamental Lemma I and III papers, we
prove a global Bessel identity for cuspidal automorphic representations of
GSp(4) which are supercuspidal at some component (plus some other local
In particular, one obtains the global Gross-Prasad Conjecture (a nonvanishing
theorem) for such representations.
On central critical values of the degree four L-functions for GSp(4): the fundamental lemma III,
with Masaaki Furusawa and Joseph Shalika
Memoirs of the AMS, Vol 225, No. 1057 (2013), x+134pp.
We extend the fundamental lemma from our
American Journal paper below, as well as one due to Furusawa-Shalika,
to the full Hecke algebra.
- Nonunique factorization and principalization
in number fields
Proceedings of the AMS, Vol. 139, No. 9 (2011), pp. 3025-3038.
This describes the number and structure of irreducible factorizations of
an algebraic integer in the ring of integers of a number field, using
what were essentially Kummer's ideas.
- A relative trace formula for a compact Riemann surface,
with Mark McKee and Eric Wambach [Corrections as of Feb. 2,
errata to the
published version, or see the corrected version on the arXiv]
International Journal of Number Theory, Vol. 7, No. 2 (2011), pp. 389-429.
We interpret a relative trace formula on a hyperbolic compact Riemann
surface as a relation between the period spectrum and ortholength
spectrum of a given closed geodesic. This leads to various asymptotic
results on periods and ortholengths, as well as some simultaneous nonvanishing
results for two different periods.
- On central critical values of the degree four
L-functions for GSp(4): the fundamental lemma II, with Masaaki
Furusawa [preprint version]
American Journal of Mathematics, Vol. 133, No. 1 (2011), pp. 197-233.
We propose a different kind of relative trace formula than Furusawa-Shalika
to relate central spinor L-values to Bessel periods, and prove the
corresponding fundamental lemma. This relative trace formula has several
advantages over the previous ones.
- Central L-values and toric periods
for GL(2), with David Whitehouse
International Mathematical Research Notices (IMRN) 2009, No. 1 (2009), pp. 141-191.
Using Jacquet's relative trace formula, we get a formula for the central value
of a GL(2) L-function, refining results of Waldspurger.
[Old version (Nov. 13, 2006). This uses a simpler trace formula but is much less general.]
L-values and toric periods for GL(2)
RIMS Kôkyûroku 1617,
Automorphic Representations, Automorphic
Forms, L-functions and Related Topics (2008), pp. 126-137.
This is basically an extended introduction to the above paper, ending with
an outline of the relative trace formula approach to proving special value
- Shalika periods on GL(2,D) and GL(4),
with Hervé Jacquet
Pacific Journal of Mathematics, Vol. 233, No. 2 (2007), pp. 341-370.
Here we use a relative trace formula
to study period integrals, which yield results about exterior-square L-functions, and thus about transfer to GSp(4).
Transfer from GL(2,D) to GSp(4)
Proceedings of the 9th Autumn Workshop on Number Theory,
Hakuba, Japan (2006).
These are notes from a talk explaining an application of my work with Jacquet
(above) to the question of transferring representations to GSp(4).
- Four-dimensional Galois representations of solvable type and automorphic forms
Ph.D. Thesis, Caltech, 2004.
This contains the results in the two papers below, as well as a
classification of representations into GSp(4,C) of solvable type and
minor additional modularity results.
I wrote an informal note about
my thesis for
(by which I mean the mathematically- or scientifically- minded layman).
Comptes Rendus Mathematique, Vol. 339, No. 2 (2004), 99-102.
This proves a new case of modularity
for four-dimensional Galois representations induced from a non-normal
quartic extension. In particular, one obtains examples of modular
representations which are not essentially self-dual.
A symplectic case of Artin's conjecture
Mathematical Research Letters, Vol. 10, No. 4 (2003), 483-492.
This gives a new case of Artin's conjecture in GSp(4,C) by establishing
the more general Langlands' reciprocity law in this case.
Undergraduate Research Supervised