arXiv subjects

Bipin R. Desai

Publications and source records attributed to Bipin R. Desai.

12 recordsLinked to original sources

arXiv2009

Neutrino Condensate as Origin of Dark Energy

We propose a new solution to the origin of dark energy. We suggest that it was created dynamically from the condensate of a singlet neutrino at a late epoch of the early Universe through its effective self interaction. This singlet neutrino is also the Dirac partner of one of the three observed neutrinos, hence dark energy is related to neutrino mass. The onset of this condensate formation in the early Universe is also related to matter density and offers an explanation of the coincidence problem of why dark energy (70%) and total matter (30%) are comparable at the present time. We demonstrate this idea in a model of neutrino mass with (right-handed) singlet neutrinos and a singlet scalar.

hep-ph↗

arXiv2006

See-saw fermion masses in an SO(10) GUT

In this work we study an SO(10) GUT model with minimum Higgs representations belonging only to the 210 and 16 dimensional representations of SO(10). We add a singlet fermion S in addition to the usual 16 dimensional representation containing quarks and leptons. There are no Higgs bi-doublets and so charged fermion masses come from one-loop corrections. Consequently all the fermion masses, Dirac and Majorana, are of the see-saw type. We minimize the Higgs potential and show how the left-right symmetry is broken in our model where it is assumed that a D-parity odd Higgs field gets a vacuum expectation value at the grand unification scale. From the renormalization group equations we infer that in our model unification happens at 10^{15} GeV and left-right symmetry can be extended up to some values just above 10^{11} GeV. The Yukawa sector of our model is completely different from most of the standard grand unified theories and we explicitly show how the Yukawa sector will look like in the different phases and briefly comment on the running of the top quark mass. We end with a brief analysis of lepton number asymmetry generated from the interactions in our model.

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arXiv2005

Large neutrino mixing angles for type-I see-saw mechanism in SO(10) GUT

We consider the neutrino mixing angles in an SO(10) GUT with the usual Higgs structure in which neutrino masses are explained by the type-I see-saw mechanism. The Dirac-neutrino Yukawa matrix then has a structure similar to that of the $u$-quark. We determine the light neutrino mass matrix through type-I see-saw mechanism using the experimentally consistent $u$-quark Yukawa matrix. We find that large neutrino mixing-angles emerge naturally in this model.

hep-ph↗

arXiv2004

An SO(10) GUT With See-Saw Masses For All Fermions

We propose an SO(10) grand unified theory which has the simplest Higgs structure discussed so far in the literature. We include only two Higgs scalars, a 210-plet and a 16-plet. In addition to the regular fermions we include one singlet, whose mass term breaks chiral symmetry, so that fermions can get masses. All fermions acquire see-saw masses, since there are no Higgs bi-doublets. Required neutrino masses with large mixing as well as leptogenesis are possible in this model.

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arXiv2003

Solutions to the Renormalization Group Equations for Yukawa Matrices as an Answer to the Quark and Lepton Mass Problem

If the scale dependence of a Yukawa matrix is assumed to be determined entirely by the dominant 33-element, then the renormalization group equations can be expressed in terms of two separate equations: a differential equation for the 33-coupling, and, an algebraic equation for the scale-independent 3x3 matrix that is found to have only two non-trivial, hierarchical, solutions with eigenvalues (0,0,1) and (0,1,1). The mass matrices are constructed from these solutions by rotating them first by the experimentally known mixing matrices-the CKM for quarks and charged leptons, and the CKM-analog for the seesaw generated Majorana neutrinos-and then incorporating the appropriate texture zeros. A uniform, hierarchical, description for the mass matrices of quarks and leptons is thus achieved, in terms of the mixing paramters, that give mass eigenvalues consistent with experiments as well as reproduce the input mixing angles. Inverted hierarchy in neutrinos is also discussed. Only a single scale (approx. 10^13 GeV) for the seesaw neutrinos is involved rather than their mass distribution. No new particles are otherwise invoked.

hep-ph↗

arXiv2002

Three-Neutrino Mass Matrices with Two Texture Zeros

Out of the fifteen 3 x 3 neutrino mass matrices with two texture zeros seven are compatible with the neutrino oscillation data. While 2 of them correspond to hierarchical neutrino masses and 1 to an inverted hierarchy, the remaining 4 correspond to degenerate masses. Moreover only the first 3 of the 7 mass matrices are compatible with the maximal mixing angle of atmospheric neutrino and hence favoured by data. We give compact expressions for mass matrices in terms of mass eigenvalues and study phenomenological implications for the 7 cases. Similarity of the textures of the neutrino, charged-lepton mass matrices with those of quark mass matrices is also discussed.

hep-ph↗

arXiv2000

Extra Dimensions and Compositeness as a Basis for Hierarchy in Quark Mass Matrices

Strong gauge and top-Yukawa couplings predicted in the presence of extra dimensions lead to a trickle-down effect of the top-coupling through the renormalization group equations for the quark Yukawa matrices. The matrix elements for the u and d-quarks get progressively smaller as one moves away from the dominant (33)-element revealing a hierarchical pattern for the mass matrices.

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arXiv2000

Possible textures of neutrino and charged lepton mass matrices

We study a variety of different texture patterns in the basis in which the charged lepton mass matrix or neutrino mass matrix or neither are diagonal. The experimental results on the neutrinos provide sufficient restrictions to allow only a small number of simple patterns. We discuss particularly the texture zeroes which provide important relations among the mass eigenvalues and the mixing matrix.

hep-ph↗

arXiv2000

Quark Mass Matrices with Four and Five Texture Zeroes, and the CKM Matrix, in terms of Mass Eigenvalues

Using the triangular matrix techniques of Kuo et al and Chiu et al for the four and five texture zero cases, with vanishing (11) elements for U and D matrices, it is shown, from the general eigenvalue equations and hierarchy conditions, that the quark mass matrices, and the CKM matrix can be expressed (except for the phases) entirely in terms of quark masses. The matrix structures are then quite simple and transparent. We confirm their results for the five texture zero case but find, upon closer examination of all the CKM elements which our results provide, that six of their nine patterns for the four texture zero case are not compatible with experiments. In total, only one five-texture zero and three four-texture zero patterns are allowed.

hep-ph↗

arXiv1999

Low Mass Higgs Boson Consistent with Precision Experiments: A Consequence of Large Top-Yukawa Coupling in Condensate Models

It is shown, using dispersion relations techniques for bound states, that the presence of a large top-Yukawa coupling lowers the Higgs mass from the condensate-model value of twice the top mass (~350 Gev) to 100-200 Gev consistent with the Z(super 0) width precision measurements. The coupling is found to be ~3.7 at the top-mass, much larger than the Standard Model value ~1. It corresponds to a compositeness scale ~1.4 Tev, which is consistent with top-color models, and implies quite different scales for fermion mass generation and electroweak symmetry breaking. A second scalar state around 1 Tev also emerges as a solution in combination with the low mass Higgs.

hep-ph↗

arXiv1999

Can the Higgs Boson Bootstrap itself?

It is pointed out that Higgs bootstrap is inherent in the top-condensate models of Nambu and Bardeen et al in that the ladder sum of Higgs pole diagrams in one channel reproduces a Higgs pole in the crossed-channel. This result is exact whenever color flows simultaneously in both channel directions e.g. for N(sub c)=1. Bootstrap solutions for the Higgs boson mass are obtained that are compatible with the condensate models such as the top-color models which imply large top-Yukawa couplings at the top mass.

hep-ph↗

arXiv1998

Pattern of Texture Zeroes in Quark Mass Matrices With a Divergent Top-Yukawa Coupling at the GUT Scale

In a SUSY GUT model responsible for generating symmetric quark mass matrices at the GUT scale (mu = Lamda) we assume that the top-Yukawa coupling, lamda_t, becomes infinite at that scale. As a consequence, the MSSM renormalization group equations for quark Yukawa couplings exhibit hierarchical solutions which lead to a pattern of texture zeroes in quark mass matrices at mu = Lamda similar to one of the solutions of Ramond, Roberts, and Ross. The evolution in energy scale to low energies shows excellent agreement between the measured quantities involving the scale-independent ratios of CKM matrix elements and their predicted values in terms of quark mass ratios. It is noted that the tt-bar condensate model of Bardeen, et al. predicts an infinite lamda_t at mu = Lamda implying, for our model, that at mu = Lamda, both the symmetry of Yukawa matrices and condensate dynamics may have a common origin.

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