arXiv subjects

Michael Harris

Publications and source records attributed to Michael Harris.

40 records · Page 3Linked to original sources

arXiv2001

On a conjecture of Jacquet

In this note, we prove in full generality a conjecture of Jacquet concerning the nonvanishing of the triple product L-function at the central point. Let $\kay$ be a number field and let $π_i$, $i=1$, 2, 3 be cuspidal automorphic representations of $GL_2(\A)$ such that the product of their central characters is trivial. Then the central value $L(\frac12,π_1\otimesπ_2\otimesπ_3)$ of the triple product L--function is nonzero if and only if there exists a quaternion algebra $B$ over $\kay$ and automorphic forms $f_i^B\in π_i^B$, such that the integral of the product $f_1^B f_2^B f_3^B$ over the diagonal $Z(\Bbb A) B^\times(\kay) B^\times(\Bbb A)$ is nonzero, where $π_i^B$ is the representation of $B^\times(\A)$ corresponding to $π_i$. In a previous paper, we proved this conjecture in the special case where $\kay=\Q$ and the $π_i$'s correspond to a triple of holomorphic newforms. Recent improvement on the Ramanujan bound due to Kim and Shahidi, results about the local L-factors due to Ikeda and Ramakrishnan, results of Chen-bo Zhu and Sahi about invariant distributions and degenerate principal series in the complex case, and an extension of the Siegel--Weil formula to similitude groups allow us to carry over our method to the general case.

math.NT↗

arXiv1997

Astrophysical Effects of nu+gamma-->nu+gamma+gamma and Its Crossed Processes

Recently, Dicus and Repko computed nu gamma --> nu gamma gamma for energies below the threshold for e^{+}e^{-} pair production. They found across section on the order of 10^{-52} omega ^{gamma} with gamma =10, where omega is the CMS energy of one of the initial particles in MeV. Cross sections for the crossed processes are the same to factors of order one. This note investigates the extent to which these processes could, if their result extrapolates past 1 MeV: affect supernova dynamics; cut off the energy distribution of very high energy cosmic photons and neutrinos; and possibly give rise to an observable gamma signal from scattering of neutrinos from one supernova by those of a second supernova close in space and time. We also estimate, from Supernova 1987A, that, in the region above a few MeV, gamma must fall below 8.4.

astro-ph↗

arXiv1996

The local Langlands conjecture for GL(n) over a p-adic field, n < p

Let F be a p-adic field and n a positive integer. The local Langlands conjecture asserts the existence of a bijection between irreducible admissible representations of GL(n,F) and n-dimensional admissible representations of the Weil-Deligne group of F. This bijection is required to satisfy certain natural compatibilities, of which the most important is compatibility with local functional equations (preservation of L and epsilon factors of pairs). It is enough to construct a bijection with these properties between supercuspidal representations of GL(n,F) and n-dimensional irreducible representations of the Weil group of F. In a previous paper, the author constructed a canonical bijection on the etale cohomology of the rigid-analytic coverings of the p-adic upper half space constructed by Drinfeld. (That the map in the previous paper is a bijection was actually proved by Henniart.) However, the compatibility of epsilon factors of pairs was not shown. The present article uses a technique of non-Galois automorphic induction to show that the bijection previously constructed is compatible with epsilon factors of pairs of representations of GL(n,F) and GL(m,F) when n and m are prime to p (the tame case). This implies the local Langlands conjecture in degree < p. It is also shown how the local Langlands conjecture in general would follow from a generalization of Carayol's theorem on the bad reduction of Shimura curves to certain Shimura varieties of higher dimension.

math.NT↗

arXiv1996

p-adic measures and square roots of triple product L-functions

Let p be a prime number, and let f, g, and h be three modular forms of weights $κ$, $λ$, and $μ$ for $SL(2,\Bbb{Z})$. We suppose $κ\geq λ+ μ$. In joint work with Kudla, one of the authors obtained a formula for the normalized {\it square root} of the value at $s = {1/2}(κ+ λ+ μ- 2)$ (the {\it central critical value}) of the triple product $L(s,f,g,h)$. We apply this formula, letting $f$ (and thus $κ$) vary in a $p$-adic analytic family ${\bold f}$ of ordinary modular forms (a Hida family). By modifying Hida's construction of the $p$-adic Rankin-Selberg convolution, we obtain a generalized $p$-adic measure whose associated analytic function gives a $p$-adic interpolation of the square roots of the central critical values of $L(s,f,g,h)$, normalized by certain universal correction factors. The archimedean correction factor is not determined explicitly. This is an example of what appears to be a very general phenomenon of $p$-adic interpolation of normalized square roots of $L$-functions along the so-called "anti-cyclotomic hyperplane." We note that the $p$-adic triple product itself has not been constructed in the half-space $κ\geq λ+ μ$.

math.NT↗