Muon (g-2) from the bulk neutrino field in a warped extra dimensional model

In the Randall-Sundrum model, a bulk neutrino field in the 5-dimensional space-time can give rise to tiny Dirac masses to neutrinos. In such a scenario, we have computed the contribution of the bulk neutrino field to the anomalous magnetic moment $(g-2)_\mu$ of muon. We have computed this contribution in the 't Hooft-Feynman gauge and have found that the contribution has the right sign to fit the current discrepancy between the experiment and the standard model value of $(g-2)_\mu$. We have also studied possible constraints on the model parameters by including contributions to $(g-2)_\mu$ from other sources such as bulk gravitons.Comment: 18 pages, 3 figures, 2 tables, minor changes, this version has been published in Physical Review

Study on Gait Efficiency and Energy Cost of Below Knee Amputees After Therapeutic Practices

An earlier research advocated that a below knee amputee (BK) with conventional trans-tibial prosthesis attains higher gait efficiency at lower energy cost with therapeutic practices of proper time and co-ordination in compare to normal subjects of similar physical parameters and quality of life. The present study focused on comparative analysis of energy cost and gait efficiency between a group of below knee amputees and a control group (normal subjects without amputation) to indicate the consistency of the earlier findings. The subjects were selected with similar physical parameters and quality of life. Oxygen Uptake (VO2) and Heart Rate (HR) were measured by Cosmed® k4 b2 analyzer system. Gait efficiency (p < 0.0001) was found higher with lower energy cost for BK amputees after therapeutic practices than control group. The therapeutic activities contributed to efficient gait pattern for amputees ensuring proper time and co-ordination with balance in consistence to the earlier research

Testing Reionization with Gamma Ray Burst Absorption Spectra

We propose to study cosmic reionization using absorption line spectra of high-redshift Gamma Ray Burst (GRB) afterglows. We show that the statistics of the dark portions (gaps) in GRB absorption spectra represent exquisite tools to discriminate among different reionization models. We then compute the probability to find the largest gap in a given width range [Wmax, Wmax + dW] at a flux threshold Fth for burst afterglows at redshifts 6.3 < z < 6.7. We show that different reionization scenarios populate the (Wmax, Fth) plane in a very different way, allowing to distinguish among different reionization histories. We provide here useful plots that allow a very simple and direct comparison between observations and model results. Finally, we apply our methods to GRB 050904 detected at z = 6.29. We show that the observation of this burst strongly favors reionization models which predict a highly ionized intergalactic medium at z~6, with an estimated mean neutral hydrogen fraction xHI = 6.4 \pm 0.3 \times 10^-5 along the line of sight towards GRB 050904.Comment: 5 pages, 3 figures, revised to match the accepted version; major change: gap statistics is now studied in terms of the flux threshold Fth, instead of the observed J-band flux FJ; MNRAS in pres

Detecting extra dimensions with gravity wave spectroscopy: the black string brane-world

Using the black string between two branes as a model of a brane-world black hole, we compute the gravity wave perturbations and identify the features arising from the additional polarizations of the graviton. The standard four-dimensional gravitational wave signal acquires late-time oscillations due to massive modes of the graviton. The Fourier transform of these oscillations shows a series of spikes associated with the masses of the Kaluza-Klein modes, providing in principle a spectroscopic signature of extra dimensions.Comment: 4 pages, 5 figures. Comments on the frequency and detectability of the massive mode signal added, and title modified. Version accepted for publication in Phys. Rev. Let

The pion-pion scattering amplitude. III: Improving the analysis with forward dispersion relations and Roy equations

We complete and improve the fits to experimental $\pi\pi$ scattering amplitudes, both at low and high energies, that we performed in the previous papers of this series. We then verify that the corresponding amplitudes satisfy analyticity requirements, in the form of partial wave analyticity at low energies, forward dispersion relations (FDR) at all energies, and Roy equations below$\bar{K}K$ threshold; the first by construction, the last two, inside experimental errors. Then we repeat the fits including as constraints FDR and Roy equations. The ensuing central values of the various scattering amplitudes verify very accurately FDR and, especially, Roy equations, and change very little from what we found by just fitting data, with the exception of the D2 wave phase shift, for which one parameter moves by $1.5 \sigma$. These improved parametrizations therefore provide a reliable representation of pion-pion amplitudes with which one can test various physical relations. We also present a list of low energy parameters and other observables. In particular, we find $a_0^{(0)}=0.223\pm0.009 M^{-1}_\pi$, $a_0^{(2)}=-0.0444\pm0.0045 M^{-1}_\pi$ and $\delta_0^{(0)}(m^2_K)-\delta_0^{(2)}(m^2_K)=50.9\pm1.2^{\rm o}$.Comment: Plain TeX. 29 figures. Version to be published in PRD, with improved P and F wave

Unification, Multiplets and Proton Decay

We make a detailed analysis of gauge coupling unification in supersymmetry. When the Standard Model gauge group is embedded in a Grand Unified Theory, new particles often appear below the GUT scale in order to predict the right phenomenology at low energy. While these new particles are beyond the reach of accelerator experiments, they change the prediction of \alpha_s. Here we classify all the (SU(3)_C,SU(2)_L,U(1)_Y) representations which improve or worsen the prediction. Running experimentally determined values of the coupling constants at two loops we calculate the allowed range of masses of fields in these representations. We explore the implication of these results in SU(5) and SU(3)^3 (trinification) models. We discover that minimal trinification predicts light triplet Higgs particles which lead to proton decay with a lifetime in the vicinity of the current experimental bound.Comment: figures replaced, new calculations and references added. A quantitative description of dependence of unification on varying input parameters as well as varying the sparticle spectrum is added. This version to appear in PR