9,731 research outputs found
Finite Weil restriction of curves
Given number fields , smooth projective curves defined over
and defined over , and a non-constant -morphism ,we consider the curve defined over whose -rational points
parametrize the -rational points on whose images under are defined
over . Our construction provides a framework which includes as a special
case that used in Elliptic Curve Chabauty techniques and their higher genus
versions. The set can be infinite only when has genus at most 1;
we analyze completely the case when has genus 1.Comment: Comments are welcome
Quark Masses and Renormalization Constants from Quark Propagator and 3-point Functions
We have computed the light and strange quark masses and the renormalization
constants of the quark bilinear operators, by studying the large-p^2 behaviour
of the lattice quark propagator and 3-point functions. The calculation is
non-perturbatively improved, at O(a), in the chiral limit. The method used to
compute the quark masses has never been applied so far, and it does not require
an explicit determination of the quark mass renormalization constant.Comment: LATTICE99 (Improvement and Renormalization) - 3 pages, 2 figure
Flux creep in Bi2Sr2Ca1Cu2O(8+x) single crystals
Dissipative effects were investigated in Bi2Sr2Ca1Cu2O(8+x) single crystals by critical current and magnetic relaxation measurements. Activation energies for the flux motion were determined from the temperature dependence of the critical current and from the time decay of the zero field cooled and the remanent magnetization. The effective activation energy was found to increase with temperature, in agreement with the existence of a distribution of activation energies (E sub o 20 meV at 4.2 K for H + 10 kOe applied parallel to the c-axis.)
Getting the Lorentz transformations without requiring an invariant speed
The structure of the Lorentz transformations follows purely from the absence
of privileged inertial reference frames and the group structure (closure under
composition) of the transformations---two assumptions that are simple and
physically necessary. The existence of an invariant speed is \textit{not} a
necessary assumption, and in fact is a consequence of the principle of
relativity (though the finite value of this speed must, of course, be obtained
from experiment). Von Ignatowsky derived this result in 1911, but it is still
not widely known and is absent from most textbooks. Here we present a
completely elementary proof of the result, suitable for use in an introductory
course in special relativity.Comment: 4 pages, 1 figur
High School Studentsâ Performances in Transitions between Different Representations of Linear Relationships in Mathematics and Physics
This study involved 643 high school students to assess their performance in using different representations of linear functionsâgraphs, tables, and algebraic relationshipsâin mathematics and kinematics. The results show that students encounter greater difficulties when they have to interpret representations involving algebraic relations in mathematics. Furthermore, it is shown how the ability to switch from one type of representation to another is influenced by spatial reasoning skills, orientation toward physics, and self-confidence in the field of mathematics and physics. Implications for teaching kinematics and linear functions are briefly discussed
Observations of one young and three middle-aged -ray pulsars with the Gran Telescopio Canarias
We used the 10.4m Gran Telescopio Canarias to search for the optical
counterparts to four isolated -ray pulsars, all detected in the X-rays
by either \xmm\ or \chan\ but not yet in the optical. Three of them are
middle-aged pulsars -- PSR\, J1846+0919 (0.36 Myr), PSR\, J2055+2539 (1.2 Myr),
PSR\, J2043+2740 (1.2 Myr) -- and one, PSR\, J1907+0602, is a young pulsar
(19.5 kyr). For both PSR\, J1907+0602 and PSR\, J2055+2539 we found one object
close to the pulsar position. However, in both cases such an object cannot be a
viable candidate counterpart to the pulsar. For PSR\, J1907+0602, because it
would imply an anomalously red spectrum for the pulsar and for PSR\, J2055+2539
because the pulsar would be unrealistically bright () for the
assumed distance and interstellar extinction. For PSR\, J1846+0919, we found no
object sufficiently close to the expected position to claim a possible
association, whereas for PSR\, J2043+2740 we confirm our previous findings that
the object nearest to the pulsar position is an unrelated field star. We used
our brightness limits (), the first obtained with a
large-aperture telescope for both PSR\, J1846+0919 and PSR\, J2055+2539, to
constrain the optical emission properties of these pulsars and investigate the
presence of spectral turnovers at low energies in their multi-wavelength
spectra.Comment: 10 pages, 11 figures, accpted for publication in MNRA
A note on the fate of the Landau-Yang theorem in non-Abelian gauge theories
Using elementary considerations of Lorentz invariance, Bose symmetry and BRST
invariance, we argue why the decay of a massive color-octet vector state into a
pair of on-shell massless gluons is possible in a non-Abelian SU(N) Yang-Mills
theory, we constrain the form of the amplitude of the process and offer a
simple understanding of these results in terms of effective-action operators.Comment: 7 pages. v2: typos corrected, one reference adde
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