293 research outputs found
The four-loop DRED gauge beta-function and fermion mass anomalous dimension for general gauge groups
We present four-loop results for the gauge beta-function and the fermion mass
anomalous dimension for a gauge theory with a general gauge group and a
multiplet of fermions transforming according to an arbitrary representation,
calculated using the dimensional reduction scheme. In the special case of a
supersymmetric theory we confirm previous calculations of both the gauge
beta-function and the gaugino mass beta-function.Comment: 44 pages, added references (v2) minor changes (v3
Meta-stable SUSY Breaking Model in Supergravity
We analyze a supersymmetry (SUSY) breaking model proposed by Intriligator,
Seiberg and Shih in a supergravity (SUGRA) framework. This is a simple and
natural setup which demands neither extra superpotential interactions nor an
additional gauge symmetry. In the SUGRA setup, the U(1)R symmetry is explicitly
broken by the constant term in the superpotential, and pseudo-moduli field
naturally takes non-zero vacuum expectation value through a vanishing
cosmological constant condition. Sfermions tend to be heavier than gauginos,
and the strong-coupling scale is determined once a ratio of sfermion to gaugino
masses is fixed.Comment: 13 page
Renormalization Group Invariants in the MSSM and Its Extensions
We derive one-loop renormalization group (RG) invariant observables and
analyze their phenomenological implications in the MSSM and its \mu problem
solving extensions, U(1)' model and NMSSM. We show that there exist several RG
invariants in the gauge, Yukawa and soft-breaking sectors of each model. In
general, RG invariants are highly useful for projecting experimental data to
messenger scale, for revealing correlations among the model parameters, and for
probing the mechanism that breaks supersymmetry. The Yukawa couplings and
trilinear soft terms in U(1)' model and NMSSM do not form RG invariants though
there exist approximate invariants in low tan(beta). In the NMSSM, there are no
invariants that contain the Higgs mass-squareds. We provide a comparative
analysis of RG invariants in all three models and analyze their model-building
and phenomenological implications by a number of case studies.Comment: 32 pages, 5 tables; extended previous analysis to include U(1)'
models and NMSSM where a comparative discussion is give
Four-loop beta function and mass anomalous dimension in Dimensional Reduction
Within the framework of QCD we compute renormalization constants for the
strong coupling and the quark masses to four-loop order. We apply the DR-bar
scheme and put special emphasis on the additional couplings which have to be
taken into account. This concerns the epsilon-scalar--quark Yukawa coupling as
well as the vertex containing four epsilon-scalars. For a supersymmetric Yang
Mills theory, we find, in contrast to a previous claim, that the evanescent
Yukawa coupling equals the strong coupling constant through three loops as
required by supersymmetry.Comment: 15 pages, fixed typo in Eq. (18
EFFECT OF REFINING ON THE PHYSICAL AND CHEMICAL PROPERTIES OF SUNFLOWER AND SOYBEAN OILS
The effect of different refining processes on the physical (colour, specific gravity, refractive index) and chemical (acidity, saponification number, ester number, iodine value, peroxide value, unsaponifiable matter) properties of sunflower and soybean oils was studied.
Degumming and dewaxing procedures caused negligible differences in the properties mentioned above.
Treatment with NaOH or KOH of 12, 14 and 16 Beâ° concentration resulted in a reasonable refining loss and residual acidity. Using NaâC0â and NaHC0â or KOH and NaOH of higher concentration (over 16 Beâ°) caused high refining losses and unacceptable residual acidity
ISS-flation
Inflation may occur while rolling into the metastable supersymmetry-breaking
vacuum of massive supersymmetric QCD. We explore the range of parameters in
which slow-roll inflation and long-lived metastable supersymmetry breaking may
be simultaneously realized. The end of slow-roll inflation in this context
coincides with the spontaneous breaking of a global symmetry, which may give
rise to significant curvature perturbations via inhomogenous preheating. Such
spontaneous symmetry breaking at the end of inflation may give rise to
observable non-gaussianities, distinguishing this scenario from more
conventional models of supersymmetric hybrid inflation.Comment: 26 page
Minimal Higher-Dimensional Extensions of the Standard Model and Electroweak Observables
We consider minimal 5-dimensional extensions of the Standard Model
compactified on an orbifold, in which the SU(2) and U(1)
gauge fields and Higgs bosons may or may not all propagate in the fifth
dimension while the observable matter is always assumed to be confined to a
4-dimensional subspace. We pay particular attention to consistently quantize
the higher-dimensional models in the generalized gauge and derive
analytic expressions for the mass spectrum of the resulting Kaluza-Klein states
and their couplings to matter. Based on recent data from electroweak precision
tests, we improve previous limits obtained in the 5-dimensional Standard Model
with a common compactification radius and extend our analysis to other possible
5-dimensional Standard-Model constructions. We find that the usually derived
lower bound of TeV on an universal compactification scale may be
considerably relaxed to TeV in a minimal scenario, in which the
SU(2) gauge boson is the only field that feels the presence of the fifth
dimension.Comment: 48 pages, LaTeX, 1 eps figure, typos correcte
Power law enhancement of neutrino mixing angles in extra dimensions
We study the renormalization of the -type Majorana neutrino mass
operator in a scenario where there is a compactified extra dimension and the
fields involved correspond to only the standard model particles and their
Kaluza-Klein excitations. We observe that in a two flavour scenario, where one
of the neutrinos is necessarily , it is indeed possible to generate a
large mixing at 100 GeV starting from a very small mixing near the
ultra-violet cutoff 30 TeV. {\em En passant}, we also derive the Higgs
mass upper and lower limits from perturbative unitarity and stability of the
potential, respectively.Comment: Latex, 6 pages, one pslatex figure; v2: clarifying remarks added,
minor typos corrected, references updated, version to appear in Phys. Rev.
Electromagnetic radiation from collisions at almost the speed of light: an extremely relativistic charged particle falling into a Schwarzschild black hole
We investigate the electromagnetic radiation released during the high energy
collision of a charged point particle with a four-dimensional Schwarzschild
black hole. We show that the spectra is flat, and well described by a classical
calculation. We also compare the total electromagnetic and gravitational
energies emitted, and find that the former is supressed in relation to the
latter for very high energies. These results could apply to the astrophysical
world in the case charged stars and small charged black holes are out there
colliding into large black holes, and to a very high energy collision
experiment in a four-dimensional world. In this latter scenario the calculation
is to be used for the moments just after the black hole formation, when the
collision of charged debris with the newly formed black hole is certainly
expected. Since the calculation is four-dimensional, it does not directly apply
to Tev-scale gravity black holes, as these inhabit a world of six to eleven
dimensions, although our results should qualitatively hold when extrapolated
with some care to higher dimensions.Comment: 6 pages, 2 figure
Unification through extra dimensions at two loops
The presence of an extra dimension of size R\equiv M_c^{-1} introduces
corrections of order (\mu/M_c)\alpha to the gauge and Yukawa couplings and
accelerates their running at scales \mu larger than M_c. This could result in a
grand unification scale M_X\approx 20 M_c. We study the corrections at the
two-loop level. We find corrections of order (\mu/M_c)\alpha^2 for the gauge
couplings and of order (\mu/M_c)^2\alpha^2 for the Yukawa couplings. Therefore,
in the Yukawa sector one and two-loop contributions can be of the same order
below M_X. We show that in the usual scenarios the dominant gauge and Yukawa
couplings are decreasing functions of the scale, in such a way that
(\mu/M_c)\alpha becomes approximately constant and two-loop contributions
introduce just a 30% correction which does not increase with the scale.Comment: 14 pages, added references, corrected typo
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