5,349 research outputs found
Constraining Proton Lifetime in SO(10) with Stabilized Doublet-Triplet Splitting
We present a class of realistic unified models based on supersymmetric SO(10)
wherein issues related to natural doublet-triplet (DT) splitting are fully
resolved. Using a minimal set of low dimensional Higgs fields which includes a
single adjoint, we show that the Dimopoulos--Wilzcek mechanism for DT splitting
can be made stable in the presence of all higher order operators without having
pseudo-Goldstone bosons and flat directions. The \mu term of order TeV is found
to be naturally induced. A Z_2-assisted anomalous U(1)_A gauge symmetry plays a
crucial role in achieving these results. The threshold corrections to
alpha_3(M_Z), somewhat surprisingly, are found to be controlled by only a few
effective parameters. This leads to a very predictive scenario for proton
decay. As a novel feature, we find an interesting correlation between the d=6
(p\to e^+\pi^0) and d=5 (p\to \nu-bar K+) decay amplitudes which allows us to
derive a constrained upper limit on the inverse rate of the e^+\pi^0 mode. Our
results show that both modes should be observed with an improvement in the
current sensitivity by about a factor of five to ten.Comment: 21 pages LaTeX, 2 figures, Few explanatory sentences and three new
references added, minor typos corrected
Eliminating the d=5 proton decay operators from SUSY GUTs
A general analysis is made of the question whether the d=5 proton decay
operators coming from exchange of colored Higgsinos can be completely
eliminated in a natural way in supersymmetric grand unified models. It is shown
that they can indeed be in SO(10) while at the same time naturally solving the
doublet-triplet splitting problem, having only two light Higgs doublets, and
using no more than a single adjoint Higgs field. Accomplishing all of this
requires that the vacuum expectation value of the adjoint Higgs field be
proportional to the generator I_{3R} rather than to B-L, as is usually assumed.
It is shown that such models can give realistic quark and lepton masses. We
also point out a new mechanism for solving the \mu problem in the context of
SO(10) SUSY GUTs.Comment: 24 pages in LaTeX, with 3 figure
DBC based Face Recognition using DWT
The applications using face biometric has proved its reliability in last
decade. In this paper, we propose DBC based Face Recognition using DWT (DBC-
FR) model. The Poly-U Near Infra Red (NIR) database images are scanned and
cropped to get only the face part in pre-processing. The face part is resized
to 100*100 and DWT is applied to derive LL, LH, HL and HH subbands. The LL
subband of size 50*50 is converted into 100 cells with 5*5 dimention of each
cell. The Directional Binary Code (DBC) is applied on each 5*5 cell to derive
100 features. The Euclidian distance measure is used to compare the features of
test image and database images. The proposed algorithm render better percentage
recognition rate compared to the existing algorithm.Comment: 15 pages,9 figures, 4 table
Inner bremsstrahlung accompanying ß decay of86rb
Inner bremsstrahlung accompanying the first-forbidden beta decay of86Rb was measured using the magnetic deflection technique with a 4.5 x 5.1 cm2Nal(Tl) crystal in the energy range 200-1660 keV. The raw spectrum was unfolded using the step-by-step process of Starfelt and Liden and compared with KUB, LF and FM theories. The measured spectrum is found to show fairly good agreement with LF theory in the energy range 200-1500 keV and it is found to deviate thereafter from all three theories. © 1985 The Institute of Physics
Heavy top quark from Fritzsch mass matrices
It is shown, contrary to common belief, that the Fritzsch ansatz for the
quark mass matrices admits a heavy top quark. With the ansatz prescribed at the
supersymmetric grand unified (GUT) scale, one finds that the top quark may be
as heavy as 145 GeV, provided that tan (the ratio of the vacuum
expectation values of the two higgs doublets) . Within a
non-supersymmetric GUT framework with two (one) light higgs doublets, the
corresponding approximate upper bound on the top mass is GeV. Our
results are based on a general one--loop renormalization group analysis of the
quark masses and mixing angles and are readily applied to alternative mass
matrix ans\"{a}tze.Comment: LaTeX, 14 figures (not included, available on request
A_4 flavour symmetry breaking scheme for understanding quark and neutrino mixing angles
We propose a spontaneous A_4 flavour symmetry breaking scheme to understand
the observed pattern of quark and neutrino mixing. The fermion mass eigenvalues
are arbitrary, but the mixing angles are constrained in such a way that the
overall patterns are explained while also leaving sufficient freedom to fit the
detailed features of the observed values, including CP violating phases. The
scheme realises the proposal of Low and Volkas to generate zero quark mixing
and tribimaximal neutrino mixing at tree-level, with deviations from both
arising from small corrections after spontaneous A_4 breaking. In the neutrino
sector, the breaking is A_4 --> Z_2, while in the quark and charged-lepton
sectors it is A_4 --> Z_3 = C_3. The full theory has A_4 completely broken, but
the two different unbroken subgroups in the two sectors force the dominant
mixing patterns to be as stated above. Radiative effects within each sector are
shown to deviate neutrino mixing from tribimaximal, while maintaining zero
quark mixing. Interactions between the two sectors -- "cross-talk" -- induce
nonzero quark mixing, and additional deviation from tribimaximal neutrino
mixing. We discuss the vacuum alignment challenge the scenario faces, and
suggest three generic ways to approach the problem. We follow up one of those
ways by sketching how an explicit model realising the symmetry breaking
structure may be constructed.Comment: 14 pages, no figures; v3: Section 5 rewritten to correct an error;
new section added to the appendix; added references; v4: minor change to
appendix C, version to be published by JHE
The Stability of the Gauge Hierarchy in
It has been shown that the Dimopoulos-Wilczek (or missing-VEV) mechanism for
doublet-triplet splitting can be implemented in models,
which requires no adjoint Higgs fields. This is an advantage from the point of
view of string theory construction. Here the stability of the gauge hierarchy
is examined in detail, and it is shown that it can be guaranteed much more
simply than in . In fact a symmetry ensures the stability of the
DW form of the expectation values to all orders in GUT-scale VEVs. It is also
shown that models based on have the advantages of while permitting complete quark-lepton unification as in
.Comment: 13 pages, LaTe
Hierarchy and Feedback in the Evolution of the E. coli Transcription Network
The E.coli transcription network has an essentially feedforward structure,
with, however, abundant feedback at the level of self-regulations. Here, we
investigate how these properties emerged during evolution. An assessment of the
role of gene duplication based on protein domain architecture shows that (i)
transcriptional autoregulators have mostly arisen through duplication, while
(ii) the expected feedback loops stemming from their initial cross-regulation
are strongly selected against. This requires a divergent coevolution of the
transcription factor DNA-binding sites and their respective DNA cis-regulatory
regions. Moreover, we find that the network tends to grow by expansion of the
existing hierarchical layers of computation, rather than by addition of new
layers. We also argue that rewiring of regulatory links due to
mutation/selection of novel transcription factor/DNA binding interactions
appears not to significantly affect the network global hierarchy, and that
horizontally transferred genes are mainly added at the bottom, as new target
nodes. These findings highlight the important evolutionary roles of both
duplication and selective deletion of crosstalks between autoregulators in the
emergence of the hierarchical transcription network of E.coli.Comment: to appear in PNA
Antisymmetric Higgs representation in SO(10) for neutrinos
A Model based on SO(10) grand unified theory (GUT) and supersymmetry is
presented to describe observed phenomena for neutrinos. The large mixing angles
among different generations, together with the small masses, are attributed to
the Higgs boson structure at the GUT energy scale. Quantitative discussions for
these observables are given, taking into account their energy evolution.Comment: 10 page
SU(16) grandunification: breaking scales, proton decay and neutrino magnetic moment
We give a detailed renormalization group analysis for the SU(16) grandunified
group with general breaking chains in which quarks and leptons transform
separately at intermediate energies. Our analysis includes the effects of Higgs
bosons. We show that the grandunification scale could be as low as GeV and give examples where new physics could exist at relatively low
energy ( GeV). We consider proton decay in this model and show that
it is consistent with a low grandunification scale. We also discuss the
possible generation of a neutrino magnetic moment in the range of to
with a very small mass by the breaking of the embedded
SU(2) symmetry at a low energy.Comment: (16 pages in REVTEX + 6 figures not included) OITS-49
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