3,924 research outputs found
Scalar gauge fields
In this paper we give a variation of the gauge procedure which employs a
scalar gauge field, , in addition to the usual vector gauge field,
. We study this variant of the usual gauge procedure in the context
of a complex scalar, matter field with a U(1) symmetry. We will
focus most on the case when develops a vacuum expectation value via
spontaneous symmetry breaking. We find that under these conditions the scalar
gauge field mixes with the Goldstone boson that arises from the breaking of a
global symmetry. Some other interesting features of this scalar gauge model
are: (i) The new gauge procedure gives rise to terms which violate C and CP
symmetries. This may have have applications in cosmology or for CP violation in
particle physics; (ii) the existence of mass terms in the Lagrangian which
respect the new extended gauge symmetry. Thus one can have gauge field mass
terms even in the absence of the usual Higgs mechanism; (iii) the emergence of
a sine-Gordon potential for the scalar gauge field; (iv) a natural, axion-like
suppression of the interaction strength of the scalar gauge boson.Comment: 15 pages RevTex, no figures; minor corrections, to be published in
JHE
Gravitational trapping potential with arbitrary extra dimensions
We extend a recently discovered, non-singular 6 dimensional brane, solution
to D=4+n dimensions. As with the previous 6D solution the present solution
provides a gravitational trapping mechanism for fields of spin 0, 1/2, 1 and 2.
There is an important distinction between 2 extra dimensions and extra
dimensions that makes this more than a trivial extension. In contrast to
gravity in n >2 dimensions, gravity in n=2 dimensions is conformally flat. The
stress-energy tensor required by this solution has reasonable physically
properties, and for n=2 and n=3 can be made to asymptotically go to zero as one
moves away from the brane.Comment: 7 pages revtex. No figures. References added some discussions change
The C Terminus of Ku80 activates the DNA-dependent protein kinase catalytic subunit
Ku is a heterodimeric protein with double-stranded DNA end-binding activity that operates in the process of nonhomologous end joining. Ku is thought to target the DNA-dependent protein kinase (DNA-PK) complex to the DNA and, when DNA bound, can interact and activate the DNA-PK catalytic subunit (DNA-PKcs). We have carried out a 3′ deletion analysis of Ku80, the larger subunit of Ku, and shown that the C-terminal 178 amino acid residues are dispensable for DNA end-binding activity but are required for efficient interaction of Ku with DNA-PKcs. Cells expressing Ku80 proteins that lack the terminal 178 residues have low DNA-PK activity, are radiation sensitive, and can recombine the signal junctions but not the coding junctions during V(D)J recombination. These cells have therefore acquired the phenotype of mouse SCID cells despite expressing DNA-PKcs protein, suggesting that an interaction between DNA-PKcs and Ku, involving the C-terminal region of Ku80, is required for DNA double-strand break rejoining and coding but not signal joint formation. To gain further insight into important domains in Ku80, we report a point mutational change in Ku80 in the defective xrs-2 cell line. This residue is conserved among species and lies outside of the previously reported Ku70-Ku80 interaction domain. The mutational change nonetheless abrogates the Ku70-Ku80 interaction and DNA end-binding activity
Persistence to high temperatures of interlayer coherence in an organic superconductor
The interlayer magnetoresistance of the organic metal \cuscn is
studied in fields of up to 45 T and at temperatures from 0.5 K to 30 K. The
peak in seen in in-plane fields, a definitive signature of
interlayer coherence, remains to s exceeding the Anderson criterion for
incoherent transport by a factor . Angle-dependent magnetoresistance
oscillations are modeled using an approach based on field-induced quasiparticle
paths on a 3D Fermi surface, to yield the dependence of the scattering rate
. The results suggest that does not vary strongly over
the Fermi surface, and that it has a dependence due to electron-electron
scattering
Nonassociative black holes in R-flux deformed phase spaces and relativistic models of G. Perelman thermodynamics
This paper systematically explores new classes of black hole (BH) solutions
in nonassociative and noncommutative gravity by focusing on features that
generalize to higher dimensions. The theories we study are modelled on (co)
tangent Lorentz bundles (i.e. eight dimensional phase spaces) with a star
product structure determined by R-flux deformations in string theory. The
nonassociative vacuum Einstein equations involve real and complex effective
sources with coefficients which are proportional to the Planck and string
constants or their products. We develop the anholonomic frame and connection
deformation method and prove that such systems of nonlinear partial
differential equations can be decoupled and integrated in general form for a
generic off-diagonal ansatz for symmetric and non-symmetric metrics. The
coefficients of such metrics may depend on all phase space coordinates
(space-time coordinates plus energy-momentum). Conditions are given when the
generating and integration functions and effective sources define two classes
of physically important exact and parametric solutions with R-flux sources
related via nonlinear symmetries to effective cosmological constants: (1) 6D
Tangherlini BHs, which are star product and R-flux distorted to
quasi-stationary configurations and 8D black ellipsoids (BEs) and BHs; (2)
nonassocitative space-time and co-fiber space double BH and/or BE
configurations generalizing Schwarzschild - de Sitter metrics. We argue that
the concept of Bekenstein-Hawking entropy is applicable only for very special
classes of nonassociative BHs encoding conventional horizons and (anti) de
Sitter configurations. Finally, we show how analogs of the relativistic G.
Perelman geometric thermodynamic variables can be defined and computed for
general classes of off-diagonal solutions encoding nonassociative R-flux
deformations.Comment: latex2e, 11pt, 43 page
Ellipsoidal, Cylindrical, Bipolar and Toroidal Wormholes in 5D Gravity
In this paper we construct and analyze new classes of wormhole and flux
tube-like solutions for the 5D vacuum Einstein equations. These 5D solutions
possess generic local anisotropy which gives rise to a gravitational running or
scaling of the Kaluza-Klein ``electric'' and ``magnetic'' charges of these
solutions. It is also shown that it is possible to self-consistently construct
these anisotropic solutions with various rotational 3D hypersurface geometries
(i.e. ellipsoidal, cylindrical, bipolar and toroidal). The local anisotropy of
these solutions is handled using the technique of anholonomic frames with their
associated nonlinear connection structures [vst]. Through the use of the
anholonomic frames the metrics are diagonalized, in contrast to holonomic
coordinate frames where the metrics would have off-diagonal components. In the
local isotropic limit these solutions are shown to be equivalent to spherically
symmetric 5D wormhole and flux tube solutions.Comment: 27 pages ReVTeX, added references and discussion. To be published in
J. Math. Phy
The monoclinic crystal structure of -RuCl and the zigzag antiferromagnetic ground state
The layered honeycomb magnet alpha-RuCl3 has been proposed as a candidate to
realize a Kitaev spin model with strongly frustrated, bond-dependent,
anisotropic interactions between spin-orbit entangled jeff=1/2 Ru4+ magnetic
moments. Here we report a detailed study of the three-dimensional crystal
structure using x-ray diffraction on untwinned crystals combined with
structural relaxation calculations. We consider several models for the stacking
of honeycomb layers and find evidence for a crystal structure with a monoclinic
unit cell corresponding to a stacking of layers with a unidirectional in-plane
offset, with occasional in-plane sliding stacking faults, in contrast with the
currently-assumed trigonal 3-layer stacking periodicity. We report electronic
band structure calculations for the monoclinic structure, which find support
for the applicability of the jeff=1/2 picture once spin orbit coupling and
electron correlations are included. We propose that differences in the
magnitude of anisotropic exchange along symmetry inequivalent bonds in the
monoclinic cell could provide a natural mechanism to explain the spin gap
observed in powder inelastic neutron scattering, in contrast to spin models
based on the three-fold symmetric trigonal structure, which predict a gapless
spectrum within linear spin wave theory. Our susceptibility measurements on
both powders and stacked crystals, as well as neutron powder diffraction show a
single magnetic transition at TN ~ 13K. The analysis of the neutron data
provides evidence for zigzag magnetic order in the honeycomb layers with an
antiferromagnetic stacking between layers. Magnetization measurements on
stacked single crystals in pulsed field up to 60T show a single transition
around 8T for in-plane fields followed by a gradual, asymptotic approach to
magnetization saturation, as characteristic of strongly anisotropic exchange
interactions.Comment: 13 pages, 9 figures, published in Physical Review
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