3,122 research outputs found
Orbit parametrizations of theta characteristics on hypersurfaces over arbitrary fields
It is well-known that theta characteristics on smooth plane curves over a
field of characteristic different from two are in bijection with certain smooth
complete intersections of three quadrics. We generalize this bijection to
possibly singular hypersurfaces of any dimension over arbitrary fields
including those of characteristic two. It is accomplished in terms of linear
orbits of tuples of symmetric matrices instead of smooth complete intersections
of quadrics. As an application of our methods, we give a description of the
projective automorphism groups of complete intersections of quadrics
generalizing Beauville's results.Comment: 35 page
A positive proportion of cubic curves over Q admit linear determinantal representations
Can a smooth plane cubic be defined by the determinant of a square matrix
with entries in linear forms in three variables? If we can, we say that it
admits a linear determinantal representation. In this paper, we investigate
linear determinantal representations of smooth plane cubics over various
fields, and prove that any smooth plane cubic over a large field (or an ample
field) admits a linear determinantal representation. Since local fields are
large, any smooth plane cubic over a local field always admits a linear
determinantal representation. As an application, we prove that a positive
proportion of smooth plane cubics over Q, ordered by height, admit linear
determinantal representations. We also prove that, if the conjecture of
Bhargava-Kane-Lenstra-Poonen-Rains on the distribution of Selmer groups is
true, a positive proportion of smooth plane cubics over Q fail the local-global
principle for the existence of linear determinantal representations.Comment: 19 page
Super Kamiokande results: atmospheric and solar neutrinos
Atmospheric neutrino and solar neutrino data from the first phase of
Super-Kamiokande (SK-I) are presented. The observed data are used to study
atmospheric and solar neutrino oscillations. Zenith angle distributions from
various atmospheric neutrino data samples are used to estimate the neutrino
oscillation parameter region. In addition, a new result of the
measurement is presented. A dip in the distribution was observed in the
data, as predicted from the sinusoidal flavor transition probability of
neutrino oscillation. The energy spectrum and the time variation such as
day/night and seasonal differences of solar neutrino flux are measured in
Super-Kamiokande. The neutrino oscillation parameters are strongly constrained
from those measurements.Comment: 8 pages, 7 figures, Proceedings for the XXXIXth Rencontres de Moriond
on Electroweak Interactions (2004
An algorithm to obtain linear determinantal representations of smooth plane cubics over finite fields
We give a brief report on our computations of linear determinantal
representations of smooth plane cubics over finite fields. After recalling a
classical interpretation of linear determinantal representations as rational
points on the affine part of Jacobian varieties, we give an algorithm to obtain
all linear determinantal representations up to equivalence. We also report our
recent study on computations of linear determinantal representations of twisted
Fermat cubics defined over the field of rational numbers. This paper is a
summary of the author's talk at the JSIAM JANT workshop on algorithmic number
theory in March, 2016. Details will appear elsewhere
The Hasse principle for flexes on cubics and the local-global divisibility problem
A point on a smooth cubic is called a flex (or an inflection point) if the
tangent line at that point intersects with the cubic with multiplicity 3. We
prove the flexes on a smooth cubic over a global field satisfy the Hasse
principle. Moreover, we study the Hasse principle allowing exceptional sets of
positive density, following a suggestion by J.-P. Serre. We prove a smooth
cubic over a global field has a flex over the base field if and only if it has
a flex locally at a set of places of Dirichlet density strictly larger than
8/9.Comment: 21 pages. The main theorem is generalized and the proof is revised
according to J.-P. Serre's suggestion. This version also contains general
results on the Hasse principle for Galois cohomology of finite group schemes
allowing exceptional sets of positive densit
On the symmetric determinantal representations of the Fermat curves of prime degree
We prove that the defining equations of the Fermat curves of prime degree
cannot be written as the determinant of symmetric matrices with entries in
linear forms in three variables with rational coefficients. In the proof, we
use a relation between symmetric matrices with entries in linear forms and
non-effective theta characteristics on smooth plane curves. We also use some
results of Gross-Rohrlich on the rational torsion points on the Jacobian
varieties of the Fermat curves of prime degree.Comment: 11 pages; to appear in International Journal of Number Theor
Sheaf theoretic classifications of pairs of square matrices over arbitrary fields
We give classifications of linear orbits of pairs of square matrices with
non-vanishing discriminant polynomials over a field in terms of certain
coherent sheaves with additional data on closed subschemes of the projective
line. Our results are valid in a uniform manner over arbitrary fields including
those of characteristic two. This work is based on the previous work of the
first author on theta characteristics on hypersurfaces. As an application, we
give parametrizations of orbits of pairs of symmetric matrices under special
linear groups with fixed discriminant polynomials generalizing some results of
Wood and Bhargava-Gross-Wang.Comment: 22 page
Establishing neutrino mass hierarchy and CP violation by two identical detectors with different baselines using the J-PARC neutrino beam
We discuss how and to what extent one can determine the neutrino mass
hierarchy, normal or inverted, and at the same time uncover CP violation in the
lepton sector by using two identical detectors with different baselines in
neutrino oscillation experiments using low energy superbeam from the J-PARC
facility.Comment: 2 pages, 2 figures, talk given at NuFact05, 21-26 June, 2005,
Frascati, Ital
Sub-Kelvin refrigeration with dry-coolers on a rotating system
We developed a cryogenic system on a rotating table that achieves sub-Kelvin
conditions. The cryogenic system consists of a helium sorption cooler and a
pulse tube cooler in a cryostat mounted on a rotating table. Two rotary-joint
connectors for electricity and helium gas circulation enable the coolers to be
operated and maintained with ease. We performed cool-down tests under a
condition of continuous rotation at 20 rpm. We obtained a temperature of 0.23 K
with a holding time of more than 24 hours, thus complying with catalog
specifications. We monitored the system's performance for four weeks; two weeks
with and without rotation. A few-percent difference in conditions was observed
between these two states. Most applications can tolerate such a slight
difference. The technology developed is useful for various scientific
applications requiring sub-Kelvin conditions on rotating platforms.Comment: 3pages, 4 figures, to appear in Review of Scientific Instrument
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