578 research outputs found
Triplet Leptogenesis in Left-Right Symmetric Seesaw Models
We discuss scalar triplet leptogenesis in a specific left-right symmetric
seesaw model. We show that the Majorana phases that are present in the model
can be effectively used to saturate the existing upper limit on the
CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and
analyze the viability of triplet leptogenesis. It is known for this kind of
scenario that the efficiency of leptogenesis is maximal if there exists a
hierarchy between the branching ratios of the triplet decays into leptons and
Higgs particles. We show that triplet leptogenesis typically favors branching
ratios with not too strong hierarchies, since maximal efficiency can only be
obtained at the expense of suppressed CP-asymmetries.Comment: 16 pages, 5 figures, published versio
Symmetry Scheme for Amino Acid Codons
Group theoretical concepts are invoked in a specific model to explain how
only twenty amino acids occur in nature out of a possible sixty four. The
methods we use enable us to justify the occurrence of the recently discovered
twenty first amino acid selenocysteine, and also enables us to predict the
possible existence of two more, as yet undiscovered amino acids.Comment: 18 pages which include 4 figures & 3 table
A SUSY SO(10) GUT with an Intermediate Scale
We examine a superpotential for an SO(10) GUT and show that if the parameters
of the superpotential are in a certain region, the SO(10) GUT has an
intermediate symmetry which breaks down to the group of the
Standard Model at an intermediate scale GeV. In the model by the
breakdown of the symmetry right-handed neutrinos acquire mass of the
intermediate scale through a renormalizable Yukawa coupling.Comment: 36 pages, LaTeX, I fixed several mistakes as follows. 1. delete
Appendix D because there was a mistake and if I fix it, it becomes nothing
interesting. 2. matrix M(2,1,\pm 1/2) at the last half of the section 4 is
changed. COnsequent result is not essentially changed. 3. several typological
errors are fixe
Resource allocation in auditory processing of emphatically stressed stimuli in aphasia
Kimelman and McNeil (1987) suggested that improved auditory comprehension for emphatically stressed information might be attributed to recruitment of additional processing resources. This study investigated effects of emphatic stress when it was applied to target words during a semantic judgement task on the auditory processing of non-stressed targets for a lexical decision task. Response time and accuracy were analysed for this dual-task experiment. It was first established that the stimuli contained appropriately placed stressed lexical items and that all subjects benefited from the emphatic stress. Next it was established that all subjects were able to voluntarily trade processing resources in the dual task under investigation, and were able to generate a performance operating curve (POC). Normal subjects showed the predicted performance decrement on the non-stressed word in the context of the preceding stressed word; subjects with aphasia did not. Results are discussed relative to resource allocation theory with normal subjects, and a working memory explanation for aphasic subjects' performance
Implications of LEP Results for SO(10) Grandunification with Two Intermediate Stages
We consider the breaking of the grand unification group to the
standard model gauge group through several chains containing two intermediate
stages. Using the values of the gauge coupling constants at scale derived
from recent LEP data, we determine the range of their intermediate and
unification scales. In particular, we identify those chains that permit new
gauge structure at relatively low energy .Comment: (LATEX, 9 pages + 3 pages of figures not included) OITS-48
Bounds on neutrino masses from leptogenesis in type-II see-saw models
The presence of the triplet in left-right symmetric theories
leads to type-II see-saw mechanism for the neutrino masses. In these models,
assuming a normal mass hierarchy for the heavy Majorana neutrinos, we derive a
lower bound on the mass of the lightest of heavy Majorana neutrino from the
leptogenesis constraint. From this bound we establish a consistent picture for
the hierarchy of heavy Majorana neutrinos in a class of left right symmetric
models in which we identify the neutrino Dirac mass matrix with that of
Fritzsch type charged lepton mass matrix. It is shown that these values are
compatible with the current neutrino oscillation data.Comment: minor typos corrected, references added, match with published versio
Mersenne Primes, Polygonal Anomalies and String Theory Classification
It is pointed out that the Mersenne primes and associated
perfect numbers play a significant role in string
theory; this observation may suggest a classification of consistent string
theories.Comment: 10 pages LaTe
Color embeddings, charge assignments, and proton stability in unified gauge theories
Three problems in hypothetical unified theories of electromagnetic, weak, and strong interactions are discussed here. First, the problem of embedding color in any simple gauge group is solved, and a complete classification of theories where the fermion color is restricted to 1^c, 3^c, and 3^c of SU_3^c is given. Generalizations are also indicated. Second, an unbroken U_1 generated by electric charge is embedded into each of the above theories and the charge assignments analyzed. Third, the general problem of stabilizing the proton by a suitable atomic mass number A is studied for the same set of theories. It is always possible to define A if the gauge group is not too small. In many of these theories there must be fermions with weird values of A: leptons with A≠0 and quarks with A≠1/3. Examples are discussed. Some future directions of research are indicated
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