11,297 research outputs found

### Gauged $B-L$ symmetry and baryogenesis via leptogenesis at TeV scale

It is shown that the requirement of preservation of baryon asymmetry does not
rule out a scale for leptogenesis as low as 10 TeV. The conclusions are
compatible with see-saw mechanism if for example the pivot mass scale for
neutrinos is $\approx 10^{-2}$ that of the charged leptons. We explore the
parameter space $\tilde{m}_1$-$M_1$ of relevant light and heavy neutrino masses
by solving Boltzmann equations. A viable scenario for obtaining baryogenesis in
this way is presented in the context of gauged $B-L$ symmetry.Comment: 15 pages, 4 figures, references added, match with journal versio

### B-L Cosmic strings and Baryogenesis

Cosmic strings arising from breaking of the $U(1)_{B-L}$ gauge symmetry that
occurs in a wide variety of unified models can carry zero modes of heavy
Majorana neutrinos. Decaying and/or repeatedly self-interacting closed loops of
these ``$B-L$'' cosmic strings can be a non-thermal source of heavy
right-handed Majorana neutrinos whose decay can contribute to the observed
baryon asymmetry of the Universe (BAU) via the leptogenesis route. The $B-L$
cosmic strings are expected in GUT models such as SO(10), where they can be
formed at an intermediate stage of symmetry breaking well below the GUT scale
$\sim 10^{16}$ GeV; such light strings are not excluded by the CMB anisotropy
data and may well exist. We estimate the contribution of $B-L$ cosmic string
loops to the baryon-to-photon ratio of the Universe in the light of current
knowledge on neutrino masses and mixings implied by atmospheric and solar
neutrino measurements. We find that $B-L$ cosmic string loops can contribute
significantly to the BAU for $U(1)_{B-L}$ symmetry breaking scale
\eta_{B-L}\gsim 1.7\times 10^{11}\gev. At the same time, in order for the
contribution of decaying $B-L$ cosmic string loops not to exceed the observed
baryon-to-photon ratio inferred from the recent WMAP results, the lightest
heavy right-handed Majorana neutrino mass $M_1$ must satisfy the constraint
M_1 \leq 2.4 \times 10^{12}(\eta_{B-L}/10^{13}\gev)^{1/2}\gev. This may have
interesting implications for the associated Yukawa couplings in the heavy
neutrino sector and consequently for the light neutrino masses generated
through see-saw mechanism.Comment: match with the published versio

### Soliton-fermion systems and stabilised vortex loops

In several self-coupled quantum field theories when treated in semi-classical
limit one obtains solitonic solutions determined by topology of the boundary
conditions. Such solutions, e.g. magnetic monopole in unified theories
\cite{Hooft1974} \cite{Polyakov1974} or the skyrme model of hadrons have been
proposed as possible non-perturbative bound states which remain stable due to
topological quantum numbers. Furthermore when fermions are introduced, under
certain conditions one obtains zero-energy solutions
\cite{Vega1978}\cite{Jackiw1981} for the Dirac equations localised on the
soliton. An implication of such zero-modes is induced fermion number
\cite{Jackiw1977} carried by the soliton.Comment: 4 pages, presented at the 17th DAE-BRNS HEP symposium held at IIT
Kharagpur, Indi

### Arbitrary Lagrangian–Eulerian finite element method for curved and deforming surfaces: I. General theory and application to fluid interfaces

An arbitrary Lagrangian–Eulerian (ALE) finite element method for arbitrarily curved and deforming two-dimensional materials and interfaces is presented here. An ALE theory is developed by endowing the surface with a mesh whose in-plane velocity need not depend on the in-plane material velocity, and can be specified arbitrarily. A finite element implementation of the theory is formulated and applied to curved and deforming surfaces with in-plane incompressible flows. Numerical inf–sup instabilities associated with in-plane incompressibility are removed by locally projecting the surface tension onto a discontinuous space of piecewise linear functions. The general isoparametric finite element method, based on an arbitrary surface parametrization with curvilinear coordinates, is tested and validated against several numerical benchmarks. A new physical insight is obtained by applying the ALE developments to cylindrical fluid films, which are computationally and analytically found to be stable to non-axisymmetric perturbations, and unstable with respect to long-wavelength axisymmetric perturbations when their length exceeds their circumference. A Lagrangian scheme is attained as a special case of the ALE formulation. Though unable to model fluid films with sustained shear flows, the Lagrangian scheme is validated by reproducing the cylindrical instability. However, relative to the ALE results, the Lagrangian simulations are found to have spatially unresolved regions with few nodes, and thus larger errors

### The irreversible thermodynamics of curved lipid membranes

The theory of irreversible thermodynamics for arbitrarily curved lipid
membranes is presented here. The coupling between elastic bending and
irreversible processes such as intra-membrane lipid flow, intra-membrane phase
transitions, and protein binding and diffusion is studied. The forms of the
entropy production for the irreversible processes are obtained, and the
corresponding thermodynamic forces and fluxes are identified. Employing the
linear irreversible thermodynamic framework, the governing equations of motion
along with appropriate boundary conditions are provided.Comment: 62 pages, 4 figure

- …