11,727 research outputs found
Flavor Gauge Models Below the Fermi Scale
The mass and weak interaction eigenstates for the quarks of the third
generation are very well aligned, an empirical fact for which the Standard
Model offers no explanation. We explore the possibility that this alignment is
due to an additional gauge symmetry in the third generation. Specifically, we
construct and analyze an explicit, renormalizable model with a gauge boson,
, corresponding to the symmetry of the third family. Having a
relatively light (in the MeV to multi-GeV range), flavor-nonuniversal gauge
boson results in a variety of constraints from different sources. By
systematically analyzing 20 different constraints, we identify the most
sensitive probes: kaon, , and Upsilon decays, mixing,
atomic parity violation, and neutrino scattering and oscillations. For the new
gauge coupling in the range the model is shown to
be consistent with the data. Possible ways of testing the model in physics,
top and decays, direct collider production and neutrino oscillation
experiments, where one can observe nonstandard matter effects, are outlined.
The choice of leptons to carry the new force is ambiguous, resulting in
additional phenomenological implications, such as non-universality in
semileptonic bottom decays. The proposed framework provides interesting
connections between neutrino oscillations, flavor and collider physics.Comment: 44 pages, 7 figures, 3 tables; B physics constraints and references
added, conclusions unchange
Fractional Hamiltonian analysis of higher order derivatives systems
The fractional Hamiltonian analysis of 1+1 dimensional field theory is
investigated and the fractional Ostrogradski's formulation is obtained. The
fractional path integral of both simple harmonic oscillator with an
acceleration-squares part and a damped oscillator are analyzed. The classical
results are obtained when fractional derivatives are replaced with the integer
order derivatives.Comment: 13 page
Estudo bibliométrico da produção cientÃfica em pinhão-manso, no Web of Science, no perÃodo de 1945 a 2011.
bitstream/item/54652/1/CITE-08.pd
Actin assembly ruptures the nuclear envelope by prying the lamina away from nuclear pores and nuclear membranes in starfish oocytes.
The nucleus of oocytes (germinal vesicle) is unusually large and its nuclear envelope (NE) is densely packed with nuclear pore complexes (NPCs) stockpiled for embryonic development. We showed that breakdown of this specialized NE is mediated by an Arp2/3-nucleated F-actin 'shell' in starfish oocytes, in contrast to microtubule-driven tearing in mammalian fibroblasts. Here, we address the mechanism of F-actin-driven NE rupture by correlated live-cell, super-resolution and electron microscopy. We show that actin is nucleated within the lamina sprouting filopodia-like spikes towards the nuclear membranes. These F-actin spikes protrude pore-free nuclear membranes, whereas the adjoining membrane stretches accumulate NPCs associated with the still-intact lamina. Packed NPCs sort into a distinct membrane network, while breaks appear in ER-like, pore-free regions. Thereby, we reveal a new function for actin-mediated membrane shaping in nuclear rupture that is likely to have implications in other contexts such as nuclear rupture observed in cancer cells
Hamiltonian formulation of systems with linear velocities within Riemann-Liouville fractional derivatives
The link between the treatments of constrained systems with fractional
derivatives by using both Hamiltonian and Lagrangian formulations is studied.
It is shown that both treatments for systems with linear velocities are
equivalent.Comment: 10 page
Type O pure radiation metrics with a cosmological constant
In this paper we complete the integration of the conformally flat pure
radiation spacetimes with a non-zero cosmological constant , and , by considering the case . This is a
further demonstration of the power and suitability of the generalised invariant
formalism (GIF) for spacetimes where only one null direction is picked out by
the Riemann tensor. For these spacetimes, the GIF picks out a second null
direction, (from the second derivative of the Riemann tensor) and once this
spinor has been identified the calculations are transferred to the simpler GHP
formalism, where the tetrad and metric are determined. The whole class of
conformally flat pure radiation spacetimes with a non-zero cosmological
constant (those found in this paper, together with those found earlier for the
case ) have a rich variety of subclasses with zero,
one, two, three, four or five Killing vectors
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