19,293 research outputs found
II. The Standard Model in the Isotopic Foldy-Wouthuysen Representation without Higgs Bosons in the Fermion Sector. Spontaneous Breaking of Parity and "Dark Matter" Problems
The Standard Model with massive fermions is formulated in the isotopic
Foldy-Wouthuysen representation. SU(2)xU(1) - invariance of the theory in this
representation is independent of whether fermions possess mass or not, and,
consequently, it is not necessary to introduce interactions between Higgs
bosons and fermions. The study discusses a possible relation between
spontaneous breaking of parity in the isotopic Foldy-Wouthuysen representation
and the composition of elementary particles of "dark matter".Comment: 12 page
Testing Models of the Individual and Cosmological Evolutions of Powerful Radio Galaxies
We seek to develop an essentially analytical model for the evolution of
Fanaroff-Riley Class II radio galaxies as they age individually and as their
numbers vary with cosmological epoch. Such modeling is required in order to
probe in more detail the impact of radio galaxies on the growth of structures
in the universe, which appears likely to have been quite significant at z > 1.
In this first paper of a series we compare three rather sophisticated
analytical models for the evolution of linear size and lobe power of FR II
radio galaxies, those of Kaiser, Dennett-Thorpe & Alexander (1997), Blundell,
Rawlings & Willott (1999), and Manolakou & Kirk (2002). We perform
multi-dimensional Monte Carlo simulations in order to compare the predictions
of each model for radio powers, sizes, redshifts and spectral indices with
data. The observational samples used here are the low frequency radio surveys,
3CRR, 6CE and 7CRS, which are flux-limited and complete. We search for and
describe the best parameters for each model, after doing statistical tests on
them. We find that no existing model can give acceptable fits to all the
properties of the surveys considered, although the Kaiser, Dennett-Thorpe &
Alexander (1997) model gives better overall results than do the Manolakou &
Kirk (2002) or Blundell, Rawlings & Willott (1999) models for most of the tests
we performed. We suggest ways in which these models may be improved.Comment: 26 pages, 5 figures; substantially improved version, with additional
statistical tests; to appear in MNRA
Quantum Radiation of Oscillons
Many classical scalar field theories possess remarkable solutions: coherently
oscillating, localized clumps, known as oscillons. In many cases, the decay
rate of classical small amplitude oscillons is known to be exponentially
suppressed and so they are extremely long lived. In this work we compute the
decay rate of quantized oscillons. We find it to be a power law in the
amplitude and couplings of the theory. Therefore, the quantum decay rate is
very different to the classical decay rate and is often dominant. We show that
essentially all oscillons eventually decay by producing outgoing radiation. In
single field theories the outgoing radiation has typically linear growth, while
if the oscillon is coupled to other bosons the outgoing radiation can have
exponential growth. The latter is a form of parametric resonance: explosive
energy transfer from a localized clump into daughter fields. This may lead to
interesting phenomenology in the early universe. Our results are obtained from
a perturbative analysis, a non-perturbative Floquet analysis, and numerics.Comment: 16 pages, 6 figures. V2: Expanded sections 1 and 2 plus other minor
changes, added references. V3: Updated to resemble version published in Phys.
Rev. D. V4: Slight rewording in 2nd paragrap
Cosmic Evolution in Generalised Brans-Dicke Theory
We have studied the Generalised Brans-Dicke theory and obtained exact
solutions of a(t),phi(t),and omega(t) for different epochs of the cosmic
evolution .We discuss how inflation,decceleration,cosmic acceleration can
result from this solution.The time variation of G(t) is also examined.Comment: 12 pages, no figure
Seeing the Invisible Axion in the Sparticle Spectrum
I describe how under favourable circumstances the invisible axion may
manifest its existence at the LHC through the sparticle spectrum; in particular
through a gluino \sim \ln (M_P/m_{3/2}) times heavier than other gauginos.Comment: 4 pages, REVTe
Dirac neutrinos and anomaly-free discrete gauge symmetries
Relying on Dirac neutrinos allows an infinity of anomaly-free discrete gauge
symmetries to be imposed on the Supersymmetric Standard Model, some of which
are GUT-compatible.Comment: 24 pages, minor changes, existence of flipped discrete gauge
symmetries is pointed ou
Higgs-Flavor Groups, Naturalness, and Dark Matter
In the absence of low-energy supersymmetry, a multiplicity of weak-scale
Higgs doublets would require additional fine-tunings unless they formed an
irreducible multiplet of a non-abelian symmetry. Remnants of such symmetry
typically render some Higgs fields stable, giving several dark matter particles
of various masses. The non-abelian symmetry also typically gives simple,
testable mass relations.Comment: Some comments added after Eqs. (2) and (12
NVV auger spectra from W(100)
The NVV Auger spectrum from a clean W(100) surface has been measured in the second derivative, d^2N (E)/dE^2, mode to enhance fine structure. This measurement is compared with spectra generated from both the selfâconvolution of the tungsten valenceâband bulk density of states (obtained from a relativistic APW energy band calculation) and a "restricted convolution" in which only transitions involving electrons from the same valence energy are allowed. The restricted convolution for a model of the Auger process in which both N_6VV and N_7VV transitions contribute offers the best match of theory and experiment. No distinct evidence of Auger emission involving the surface resonance present on W(100) is observed. Effects of H_2 and O_2 adsorption on the Auger spectrum of the W(100) surface are reported
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