
Page 


3  Connected Components of Moduli Stacks of Torsors via Tamagawa Numbers Behrend, Kai; Dhillon, Ajneet
Let $X$ be a smooth projective geometrically connected curve over
a finite field with function field $K$. Let $\G$ be a connected semisimple group
scheme over $X$. Under certain hypotheses we prove the equality of
two numbers associated with $\G$.
The first is an arithmetic invariant, its Tamagawa number. The second
is a geometric invariant, the number of connected components of the moduli
stack of $\G$torsors on $X$. Our results are most useful for studying
connected components as much is known about Tamagawa numbers.


29  The Minimal Resolution Conjecture for Points on the Cubic Surface Casanellas, M.
In this paper we prove that a generalized version of the Minimal
Resolution Conjecture given by Musta\c{t}\v{a} holds for certain
general sets of points on a smooth cubic surface $X \subset
\PP^3$. The main tool used is Gorenstein liaison theory and, more
precisely, the relationship between the free resolutions of two linked schemes.


50  Composition operators on $\mu$Bloch spaces Chen, Huaihui; Gauthier, Paul
Given a positive continuous function $\mu$ on the
interval $0<t\le1$, we consider the space of socalled $\mu$Bloch
functions on the unit ball. If $\mu(t)=t$, these are the classical
Bloch functions. For $\mu$, we define a metric $F_z^\mu(u)$ in
terms of which we give a characterization of $\mu$Bloch functions.
Then, necessary and sufficient conditions are obtained in order that
a composition operator be a bounded or compact operator between
these generalized Bloch spaces. Our results extend those of Zhang
and Xiao.


76  Ascent Properties of Auslander Categories Christensen, Lars Winther; Holm, Henrik
Let $R$ be a homomorphic image of a Gorenstein local ring. Recent
work has shown that there is a bridge between Auslander categories
and modules of finite Gorenstein homological dimensions over $R$.


109  The Ample Cone of the Kontsevich Moduli Space Coskun, Izzet; Harris, Joe; Starr, Jason
We produce ample (resp.\ NEF, eventually free) divisors in the
Kontsevich space $\Kgnb{0,n} (\mathbb P^r, d)$ of $n$pointed,
genus $0$, stable maps to $\mathbb P^r$, given such divisors in
$\Kgnb{0,n+d}$. We prove that this produces all ample (resp.\ NEF,
eventually free) divisors in $\Kgnb{0,n}(\mathbb P^r,d)$.
As a consequence, we construct a contraction of the boundary
$\bigcup_{k=1}^{\lfloor d/2 \rfloor} \Delta_{k,dk}$ in
$\Kgnb{0,0}(\mathbb P^r,d)$, analogous to a contraction of
the boundary $\bigcup_{k=3}^{\lfloor n/2 \rfloor}
\tilde{\Delta}_{k,nk}$ in $\kgnb{0,n}$ first constructed by Keel
and McKernan.


124  Characterizing Complete Erd\H os Space Dijkstra, Jan J.; Mill, Jan van
The space now known as {\em complete Erd\H os
space\/} $\cerdos$ was introduced by Paul Erd\H os in 1940 as the
closed subspace of the Hilbert space $\ell^2$ consisting of all
vectors such that every coordinate is in the convergent sequence
$\{0\}\cup\{1/n:n\in\N\}$. In a solution to a problem posed by Lex G.
Oversteegen we present simple and useful topological
characterizations of $\cerdos$.
As an application we determine the class
of factors of $\cerdos$. In another application we determine
precisely which of the spaces that can be constructed in the Banach
spaces $\ell^p$ according to the `Erd\H os method' are homeomorphic
to $\cerdos$. A novel application states that if $I$ is a
Polishable $F_\sigma$ideal on $\omega$, then $I$ with the Polish
topology is homeomorphic to either $\Z$, the Cantor set $2^\omega$,
$\Z\times2^\omega$, or $\cerdos$. This last result answers a
question that was asked
by Stevo Todor{\v{c}}evi{\'c}.


141  On the Littlewood Problem Modulo a Prime Green, Ben; Konyagin, Sergei
Let $p$ be a prime, and let $f \from \mathbb{Z}/p\mathbb{Z} \rightarrow
\mathbb{R}$ be a function with $\E f = 0$ and $\Vert \widehat{f}
\Vert_1 \leq 1$. Then
$\min_{x \in \Zp} f(x) = O(\log p)^{1/3 + \epsilon}$.
One should think of $f$ as being ``approximately continuous''; our
result is then an ``approximate intermediate value theorem''.
As an immediate consequence we show that if $A \subseteq \Zp$ is a
set of cardinality $\lfloor p/2\rfloor$, then
$\sum_r \widehat{1_A}(r) \gg (\log p)^{1/3  \epsilon}$. This
gives a result on a ``mod $p$'' analogue of Littlewood's wellknown
problem concerning the smallest possible $L^1$norm of the Fourier
transform of a set of $n$ integers.


165  Exponents of Diophantine Approximation in Dimension Two Laurent, Michel
Let $\Theta=(\alpha,\beta)$ be a point in $\bR^2$, with $1,\alpha,
\beta$ linearly independent over $\bQ$. We attach to $\Theta$ a
quadruple $\Omega(\Theta)$ of exponents that measure the quality
of approximation to $\Theta$ both by rational points and by
rational lines. The two ``uniform'' components of $\Omega(\Theta)$
are related by an equation due to Jarn\'\i k, and the four
exponents satisfy two inequalities that refine Khintchine's
transference principle. Conversely, we show that for any quadruple
$\Omega$ fulfilling these necessary conditions, there exists
a point $\Theta\in \bR^2$ for which $\Omega(\Theta) =\Omega$.


190  Bounded Hankel Products on the Bergman Space of the Polydisk Lu, Yufeng; Shang, Shuxia
We consider the problem of determining for which square integrable
functions $f$ and $g$ on the polydisk the densely defined Hankel
product $H_{f}H_g^\ast$ is bounded on the Bergman space of the
polydisk. Furthermore, we obtain similar results for the mixed
Haplitz products $H_{g}T_{\bar{f}}$ and $T_{f}H_{g}^{*}$, where $f$
and $g$ are square integrable on the polydisk and $f$ is analytic.


205  Representations of NonNegative Polynomials, Degree Bounds and Applications to Optimization Marshall, M.
Natural sufficient conditions for a polynomial to have a local minimum
at a point are considered. These conditions tend to hold with
probability $1$. It is shown that polynomials satisfying these
conditions at each minimum point have nice presentations in terms of
sums of squares. Applications are given to optimization on a compact
set and also to global optimization. In many cases, there are degree
bounds for such presentations. These bounds are of theoretical
interest, but they appear to be too large to be of much practical use
at present. In the final section, other more concrete degree bounds
are obtained which ensure at least that the feasible set of solutions
is not empty.


222  Klyachko Models for General Linear Groups of Rank 5 over a $p$Adic Field Nien, Chufeng
This paper shows the existence and uniqueness of Klyachko models for
irreducible unitary representations of $\GL_5(\CF)$, where $\CF$ is
a $p$adic field. It is an extension of the work of Heumos and Rallis on $\GL_4(\CF)$.

