921 research outputs found
Scanning Electron Microscope (SEM) of Leaf Cell Morphology and Inheritance for Corn Leaf Aphid (CLA) Resistance in Maize
Duality and Braiding in Twisted Quantum Field Theory
We re-examine various issues surrounding the definition of twisted quantum
field theories on flat noncommutative spaces. We propose an interpretation
based on nonlocal commutative field redefinitions which clarifies previously
observed properties such as the formal equivalence of Green's functions in the
noncommutative and commutative theories, causality, and the absence of UV/IR
mixing. We use these fields to define the functional integral formulation of
twisted quantum field theory. We exploit techniques from braided tensor algebra
to argue that the twisted Fock space states of these free fields obey
conventional statistics. We support our claims with a detailed analysis of the
modifications induced in the presence of background magnetic fields, which
induces additional twists by magnetic translation operators and alters the
effective noncommutative geometry seen by the twisted quantum fields. When two
such field theories are dual to one another, we demonstrate that only our
braided physical states are covariant under the duality.Comment: 35 pages; v2: Typos correcte
Maxwell-like Lagrangians for higher spins
We show how implementing invariance under divergence-free gauge
transformations leads to a remarkably simple Lagrangian description of massless
bosons of any spin. Our construction covers both flat and (A)dS backgrounds and
extends to tensors of arbitrary mixed-symmetry type. Irreducible and traceless
fields produce single-particle actions, while whenever trace constraints can be
dispensed with the resulting Lagrangians display the same reducible,
multi-particle spectra as those emerging from the tensionless limit of free
open-string field theory. For all explored options the corresponding kinetic
operators take essentially the same form as in the spin-one, Maxwell case.Comment: 77 pages, revised version. Erroneous interpretation and proof of the
gauge-fixing procedure for mixed-symmetry fields corrected. As a consequence,
the mixed-symmetry, one-particle Lagrangians are to be complemented with
conditions on the divergences of the fields; all other conclusions unchanged.
Additional minor changes including references added. To appear in JHE
On the cubic interactions of massive and partially-massless higher spins in (A)dS
Cubic interactions of massive and partially-massless totally-symmetric
higher-spin fields in any constant-curvature background of dimension greater
than three are investigated. Making use of the ambient-space formalism, the
consistency condition for the traceless and transverse parts of the
parity-invariant interactions is recast into a system of partial differential
equations. The latter can be explicitly solved for given s_1-s_2-s_3 couplings
and the 2-2-2 and 3-3-2 examples are provided in detail for general choices of
the masses. On the other hand, the general solutions for the interactions
involving massive and massless fields are expressed in a compact form as
generating functions of all the consistent couplings. The St\"uckelberg
formulation of the cubic interactions as well as their massless limits are also
analyzed.Comment: 42 pages, 2 tables, LaTex. Comments on two-derivative couplings
involving partially-massless spin-2 fields added, typos corrected, references
added. v2: final version to appear in JHEP. v3: formulae (3.4) and (3.9)
correcte
The Stokes Phenomenon and Quantum Tunneling for de Sitter Radiation in Nonstationary Coordinates
We study quantum tunneling for the de Sitter radiation in the planar
coordinates and global coordinates, which are nonstationary coordinates and
describe the expanding geometry. Using the phase-integral approximation for the
Hamilton-Jacobi action in the complex plane of time, we obtain the
particle-production rate in both coordinates and derive the additional
sinusoidal factor depending on the dimensionality of spacetime and the quantum
number for spherical harmonics in the global coordinates. This approach
resolves the factor of two problem in the tunneling method.Comment: LaTex 10 pages, no figur
Protein interactions in Xenopus germ plasm RNP particles
Hermes is an RNA-binding protein that we have previously reported to be found in the ribonucleoprotein (RNP) particles of Xenopus germ plasm, where it is associated with various RNAs, including that encoding the germ line determinant Nanos1. To further define the composition of these RNPs, we performed a screen for Hermes-binding partners using the yeast two-hybrid system. We have identified and validated four proteins that interact with Hermes in germ plasm: two isoforms of Xvelo1 (a homologue of zebrafish Bucky ball) and Rbm24b and Rbm42b, both RNA-binding proteins containing the RRM motif. GFP-Xvelo fusion proteins and their endogenous counterparts, identified with antisera, were found to localize with Hermes in the germ plasm particles of large oocytes and eggs. Only the larger Xvelo isoform was naturally found in the Balbiani body of previtellogenic oocytes. Bimolecular fluorescence complementation (BiFC) experiments confirmed that Hermes and the Xvelo variants interact in germ plasm, as do Rbm24b and 42b. Depletion of the shorter Xvelo variant with antisense oligonucleotides caused a decrease in the size of germ plasm aggregates and loosening of associated mitochondria from these structures. This suggests that the short Xvelo variant, or less likely its RNA, has a role in organizing and maintaining the integrity of germ plasm in Xenopus oocytes. While GFP fusion proteins for Rbm24b and 42b did not localize into germ plasm as specifically as Hermes or Xvelo, BiFC analysis indicated that both interact with Hermes in germ plasm RNPs. They are very stable in the face of RNA depletion, but additive effects of combinations of antisense oligos suggest they may have a role in germ plasm structure and may influence the ability of Hermes protein to effectively enter RNP particles
Higher-Spin Fermionic Gauge Fields and Their Electromagnetic Coupling
We study the electromagnetic coupling of massless higher-spin fermions in
flat space. Under the assumptions of locality and Poincare invariance, we
employ the BRST-BV cohomological methods to construct consistent
parity-preserving off-shell cubic 1-s-s vertices. Consistency and
non-triviality of the deformations not only rule out minimal coupling, but also
restrict the possible number of derivatives. Our findings are in complete
agreement with, but derived in a manner independent from, the
light-cone-formulation results of Metsaev and the string-theory-inspired
results of Sagnotti-Taronna. We prove that any gauge-algebra-preserving vertex
cannot deform the gauge transformations. We also show that in a local theory,
without additional dynamical higher-spin gauge fields, the non-abelian vertices
are eliminated by the lack of consistent second-order deformations.Comment: 44 pages; references added, minor changes made, to appear in JHE
ECRH-assisted plasma start-up with toroidally inclined launch: multi-machine comparison and perspectives for ITER
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