arXiv subjects
Publications and source records attributed to Vidyut Jain.
We present the full result for the divergent one-loop contribution to the effective boson Lagrangian for supergravity coupled to chiral and Yang-Mills supermultiplets. We also consider the specific case of dilaton couplings in effective supergravity Lagrangians from superstrings, for which the one-loop result is considerably simplified.
We present the full calculation of the divergent one-loop contribution to the effective boson Lagrangian for supergravity, including the Yang-Mills sector and the helicity-odd operators that arise from integration over fermion fields. The only restriction is on the Yang-Mills kinetic energy normalization function, which is taken diagonal in gauge indices, as in models obtained from superstrings.
We discuss the connection between models of fermion masses and mixing involving a string-motivated flavor/generation U(1)$_A$ gauge symmetry and the $μ$ term. We point out that in a certain class of such models the flavor physics can provide an appealing solution to the $μ$ problem, naturally yielding a $μ\sim O(m_{_W})$. A simple relationship between the $U(1)_A$ charge $q_{H}$ of the $μ$-term and the average generational $U(1)_A$ charges of the down quark and leptonic sectors is derived. Finally, we construct an explicit model illustrating our results.
We study models of fermion mass matrices based on a flavor- and generation-dependent string-motivated U(1)$_A$ gauge symmetry and report two new classes of solutions to the requisite consistency conditions. In particular, we propose that the fundamental reason underlying the striking feature $m_b, \ m_τ<< m_t$ is that all of the elements of the down-quark and charged lepton effective Yukawa matrices actually arise from higher-dimension operators, suppressed by inverse powers of the Plank mass. An explicit model embodying this idea is constructed.
We show that, for standard N=1 supergravity coupled to chiral matter, if the Kahler potential has no terms linear in chiral superfields then none are generated through quad. div. one--loop corrections. If however =0 and susy is spontaneously broken, linear terms are present and new linear terms may be generated due to nonrenormalizable couplings in K. These can potentially destabilize the weak-scale hierarchy.
We extend earlier calculations of the one-loop contributions to the effective bose Lagrangian in supergravity coupled to chiral matter. We evaluate all logarithmically divergent contributions for arbitrary background scalar fields and space-time metric. We show that, with a judicious choice of gauge fixing and of the definition of the action expansion, much of the result can be absorbed into a redefinition of the metric and a renormalization of the Kähler potential. Most of the remaining terms depend on the curvature of the Kähler metric. Further simplification occurs in models obtained from superstrings in which the Kähler Riemann tensor is covariantly constant.
We study the 3d effective field theory of a weakly coupled two Higgs-doublet scalar model at high temperature. Our model has three scalar quartic couplings and an $O(4)$ symmetry which is spontaneously broken by a nonzero scalar field $vev$ at zero temperature. Using high temperature perturbation theory, renormalization group arguments in $4-ε$ dimensions, as well as $1/N$ expansion techniques in 3 dimensions, we argue that the transition from the high temperature symmetry restoring phase to the low temperature phase is first order for a range of scalar couplings. This result is not due to gauge couplings. We discuss the implications of our results for baryogenesis in the two Higgs-doublet electroweak model, especially when the lightest neutral Higgs is heavier than the W--bosons.
We present an alternative calculation for the leading Higgs mass dependent one--loop corrections to the standard model Lagrangian, using a background field technique. Cross--sections computed from our one--loop Lagrangian provide a check of and reproduce results already obtained in the existing literature using diagrammatic methods, as well as allowing an analysis of other processes involving longitudinally polarized $W^\pm$s and $Z^0$s. We concentrate on the processes $WW\rightarrow f\bar{f}$ and $f\bar{f}\rightarrow WW$. We extend our result to the case of a two Higgs doublet model, when one of the physical Higgs is much heavier than the other particles and analyze the tree+one--loop unitarity bounds on the scale at which signs of a strongly interacting sector (or the heaviest Higgs) must turn up.
We study the effective field theory of a weakly coupled 3+1d gauged $ϕ^4$ type model at high temperature. Our model has $4N$ real scalars ($N$ complex Higgs doublets) and a gauge group $SU(2)$ which is spontaneously broken by a nonzero scalar field $vev$ at zero temperature. We find, for sufficiently large $N$, that the transition from the high temperature symmetry restoring phase to the low temperature phase can be either first order or second order depending on the ratio of the gauge coupling to the scalar self coupling.
We study the 3d effective theory of the high T Abelian Higgs model with N real scalars and gauge and scalar couplings denoted g and $λ$, respectively. We find for the three cases a) $6g^2/λ=0(1)$, b) $6g^2/λ=0(N)$ and c) $6g^2/λ=O(N^{2\over3})$ the following results: a) The O(N)+O(1) potential admits only a second order phase transition, b) The O(1) potential admits a first order transition and c) the O(N^{1\over3}) +O(1) result gives a first order transition whose strength diminshes with N.
We compute the leading and next--to--leading corrections to the finite temperature scalar potential for a 3+1 dimensional $ϕ^4$ theory using a systematic $1/N$ expansion. Our approach automatically avoids problems associated with infrared divergences in ordinary perturbation theory in $\hbar$. The leading order result does not admit a first order phase transition. The subleading result shows that the exact theory can admit at best only a very weak first order phase transition. For $N=4$ and weak scalar coupling we find that $T_1$, the temperature at which tunneling from the origin may begin in the case of a first order transition, must be less than about 0.5 percent larger than $T_2$, the temperature at which the origin changes from being a local minimum to being a local maximum. We compare our results to the effective potential found from a sum of daisy graphs.
The expressions for the $\hat{R}$--matrices for the quantum groups SO$_{q^2}$(5) and SO$_q$(6) in terms of the $\hat{R}$--matrices for Sp$_q$(2) and SL$_q$(4) are found, and the local isomorphisms of the corresponding quantum groups are established.