15,264 research outputs found
Root numbers and ranks in positive characteristic
For a global field K and an elliptic curve E_eta over K(T), Silverman's
specialization theorem implies that rank(E_eta(K(T))) <= rank(E_t(K)) for all
but finitely many t in P^1(K). If this inequality is strict for all but
finitely many t, the elliptic curve E_eta is said to have elevated rank. All
known examples of elevated rank for K=Q rest on the parity conjecture for
elliptic curves over Q, and the examples are all isotrivial.
Some additional standard conjectures over Q imply that there does not exist a
non-isotrivial elliptic curve over Q(T) with elevated rank. In positive
characteristic, an analogue of one of these additional conjectures is false.
Inspired by this, for the rational function field K = kappa(u) over any finite
field kappa with odd characteristic, we construct an explicit 2-parameter
family E_{c,d} of non-isotrivial elliptic curves over K(T) (depending on
arbitrary c, d in kappa^*) such that, under the parity conjecture, each E_{c,d}
has elevated rank.Comment: 40 pages; last version; to appear in Adv. Mat
Limits on Electron Neutrino Disappearance from the KARMEN and LSND electron neutrino - Carbon Cross Section Data
This paper presents a combined analysis of the KARMEN and LSND nu_e-carbon
cross section measurements within the context of a search for nu_e
disappearance at high Delta m^2. KARMEN and LSND were located at 17.7 m and
29.8 m respectively from the neutrino source, so the consistency of the two
measurements, as a function of antineutrino energy, sets strong limits on
neutrino oscillations. Most of the allowed region from the nu_e disappearance
analysis of the Gallium calibration data is excluded at >95% CL and the best
fit point is excluded at 3.6. Assuming CPT conservation, comparisons
are also made to the oscillation analyses of reactor antineutrino data.Comment: Published versio
On the design of a triaxial accelerometer
Up to now, mainly uniaxial accelerometers are described in most publications concerning this subject. However, triaxial accelerometers are needed in the biomedical field. Commercially available triaxial accelerometers consisting of three orthogonally positioned uniaxial devices do not meet all specifications of the biomedical application. Therefore, a new highly symmetrical inherently triaxial accelerometer is being developed, the advantages of which are higher sensitivity and reduction of off-axis sensitivity
Polydimethylsiloxane as an elastic material applied in a capacitive accelerometer
Polydimethylsiloxane is a silicone rubber. It has a unique flexibility, resulting in one of the lowest glass-transition temperatures of any polymer. Furthermore, it shows a low elasticity change versus temperature, a high thermal stability, chemical inertness, dielectric stability, shear stability and high compressibility. Because of its high flexibility and the very low drift of its properties with time and temperature, polydimethylsiloxane could be well suited for mechanical sensors, such as accelerometers. A novel capacitive accelerometer with polydimethylsiloxane layers as springs has been realized. The obtained measurement results are promising and show a good correspondence with the theoretical values
Design of environmental-friendly water hydraulic motion control systems for industrial applications
The Living ROMP of trans-Cyclooctene
The living ring-opening metathesis polymerization (ROMP) of trans-cyclooctene (tCO) was investigated. ROMP of tCO in the presence of PPh_3 in THF leads to the formation of narrowly dispersed polycyclooctene (PCO). The presence of PPh3 as an additive and the use of THF as a solvent were demonstrated to be necessary to suppress competing secondary metathesis processes in the ROMP of tCO. Under optimal conditions, narrowly dispersed PCO was achieved without high molecular weight contaminates. The PCO was then hydrogenated to form linear, narrowly dispersed polyethylene with a melting temperature of 139 °C. Protected, hydroxy-functionalized tCO was polymerized by this method to afford narrowly dispersed, hydroxylated PCO. Block copolymers containing polynorbornene and PCO or containing differentially functionalized PCO were also synthesized and hydrogenated to form block copolymers containing blocks of linear, narrowly dispersed polyethylene
Confronting the short-baseline oscillation anomalies with a single sterile neutrino and non-standard matter effects
We examine the MiniBooNE neutrino, MiniBooNE antineutrino and LSND
antineutrino data sets in a two-neutrino
oscillation approximation subject to non-standard matter effects. We assume
those effects can be parametrized by an -independent effective potential,
, experienced only by an intermediate, non-weakly-interacting
(sterile) neutrino state which we assume participates in the oscillation, where
corresponds to neutrino/antineutrino propagation. We discuss the
mathematical framework in which such oscillations arise in detail, and derive
the relevant oscillation probability as a function of the vacuum oscillation
parameters and , and the matter effect
parameter . We are able to successfully fit all three data sets, including
the MiniBooNE low energy excess, with the following best-fit model parameters:
eV, , and
eV. The -probability for the best fit
corresponds to 21.6%, to be compared to 6.8% for a fit where has been set
to zero, corresponding to a (3+1) sterile neutrino oscillation model. We find
that the compatibility between the three data sets corresponds to 17.4%, to be
compared to 2.3% for . Finally, given the fit results, we examine
consequences for reactor, solar, and atmospheric oscillations. For this paper,
the presented model is empirically driven, but the results obtained can be
directly used to investigate various phenomenological interpretations such as
non-standard matter effects.Comment: 19 pages, 11 figures, 1 tabl
Spacelab mission dependent training parametric resource requirements study
Training flows were developed for typical missions, resource relationships analyzed, and scheduling optimization algorithms defined. Parametric analyses were performed to study the effect of potential changes in mission model, mission complexity and training time required on the resource quantities required to support training of payload or mission specialists. Typical results of these analyses are presented both in graphic and tabular form
Polarization effects in attosecond photoelectron spectroscopy
We study the influence of polarization effects in streaking by combined atto-
and femtosecond pulses. The polarization-induced terms alter the streaking
spectrum. The normal streaking spectrum, which maps to the vector potential of
the femtosecond pulse, is modified by a contribution following the field
instead. We show that polarization effects may lead to an apparent temporal
shift, that needs to be properly accounted for in the analysis. The effect may
be isolated and studied by angle-resolved photoelectron spectroscopy from
oriented polar molecules. We also show that polarization effects will lead to
an apparent temporal shift of 50 as between photoelectrons from a 2p and 1s
state in atomic hydrogen.Comment: 4 pages, 3 figure
- …