4,432 research outputs found
Dual descriptions of massive spin-3 particles in via Noether gauge embedment
We present here a relationship among massive self-dual models for spin-3
particles in via the Noether Gauge Embedment procedure.
Starting with a first order model (in derivatives) we have obtained
a sequence of four self-dual models where . We
demonstrate that the procedure generate the correct action for the
auxiliary fields automatically. We obtain the whole action for the order
self-dual model including all the needed auxiliary fields to get rid of the
ghosts of the theory.Comment: 16 pages, 1 tabl
Master actions for massive spin-3 particles in D=2+1
We present here a relationship among massive self-dual models for spin-3
particles in via the master action procedure. Starting with a first
order model (in derivatives) we have constructed a master action
which interpolates among a sequence of four self-dual models where
. By analyzing the particle content of mixing terms, we give
additional arguments that explain why it is apparently impossible to jump from
the fourth order model to a higher order model. We have also analyzed
similarities and differences between the fourth order -term in the spin-2
case and the analogous fourth order term in the spin-3 context.Comment: 16 page
Effective action for a quantum scalar field in warped spaces
We investigate the one-loop corrections at zero, as well as finite
temperature, of a scalar field taking place in a braneworld motived warped
background. After to reach a well defined problem, we calculate the effective
action with the corresponding quantum corrections to each case.Comment: 10 pages, to appear in The European Physical Journal
Turning it inside out: The organization of human septin heterooligomers.
Septin family proteins are quite similar to each other both within and between eukaryotic species. Typically, multiple discrete septins co-assemble into linear heterooligomers (usually hexameric or octameric rods) with a variety of cellular functions. We know little about how incorporation of different septins confers different properties to such complexes. This issue is especially acute in human cells where 13 separate septin gene products (often produced in multiple forms arising from alternative start codons and differential splicing) are expressed in a tissue-specific manner. Based on sequence alignments and phylogenetic criteria, human septins fall into four distinct groups predictive of their interactions, that is, members of the same group appear to occupy the same position within oligomeric septin protomers, which are "palindromic" (have twofold rotational symmetry about a central homodimeric pair). Many such protomers are capable of end-to-end polymerization, generating filaments. Over a decade ago, a study using X-ray crystallography and single-particle electron microscopy deduced the arrangement within recombinant heterohexamers comprising representatives of three human septin groups-SEPT2, SEPT6, and SEPT7. This model greatly influenced subsequent studies of human and other septin complexes, including how incorporating a septin from a fourth group forms heterooctamers, as first observed in budding yeast. Two recent studies, including one in this issue of Cytoskeleton, provide clear evidence that, in fact, the organization of subunits within human septin heterohexamers and heterooctamers is inverted relative to the original model. These findings are discussed here in a broader context, including possible causes for the initial confusion
Massive "spin-2" theories in arbitrary dimensions
Here we show that in arbitrary dimensions there are two families of
second order Lagrangians describing massive "spin-2" particles via a
nonsymmetric rank-2 tensor. They differ from the usual Fierz-Pauli theory in
general. At zero mass one of the families is Weyl invariant. Such massless
theory has no particle content in and gives rise, via master action, to a
dual higher order (in derivatives) description of massive spin-2 particles in
where both the second and the fourth order terms are Weyl invariant,
contrary to the linearized New Massive Gravity. However, only the fourth order
term is invariant under arbitrary antisymmetric shifts. Consequently, the
antisymmetric part of the tensor propagates at large momentum as
instead of . So, the same kind of obstacle for the
renormalizability of the New Massive Gravity reappears in this nonsymmetric
higher order description of massive spin-2 particles.Comment: 11 pages, 0 figure
Massive spin-2 particles via embedment of the Fierz-Pauli equations of motion
Here we obtain alternative descriptions of massive spin-2 particles by an
embedding procedure of the Fierz-Pauli equations of motion. All models are free
of ghosts at quadratic level although most of them are of higher order in
derivatives. The models that we obtain can be nonlinearly completed in terms of
a dynamic and a fixed metric. They include some massive gravities
recently considered in the literature. In some cases there is an infrared (no
derivative) modification of the Fierz-Pauli mass term altogether with higher
order terms in derivatives. The analytic structure of the propagator of the
corresponding free theories is not affected by the extra terms in the action as
compared to the usual second order Fierz-Pauli theory.Comment: 13 page
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