Geometry of deformations of branes in warped backgrounds

The `braneworld' (described by the usual worldvolume action) is a D dimensional timelike surface embedded in a N dimensional ($N>D$) warped, nonfactorisable spacetime. We first address the conditions on the warp factor required to have an extremal flat brane in a five dimensional background. Subsequently, we deal with normal deformations of such extremal branes. The ensuing Jacobi equations are analysed to obtain the stability condition. It turns out that to have a stable brane, the warp factor should have a minimum at the location of the brane in the given background spacetime. To illustrate our results we explicitly check the extremality and stability criteria for a few known co-dimension one braneworld models. Generalisations of the above formalism for the cases of (i) curved branes (ii) asymmetrical warping and (iii) higher co-dimension braneworlds are then presented alongwith some typical examples for each. Finally, we summarize our results and provide perspectives for future work along these lines.Comment: 21 pages. Version matching final version. Accepted for publication in Class. Quant. Gra

Orbifold resolutions with general profile

A very general class of resolved versions of the C/Z_N, T^2/Z_N and S^1/Z_2 orbifolds is considered and the free theory of 6D chiral fermions studied on it. As the orbifold limit is taken, localized 4D chiral massless fermions are seen to arise at the fixed points. Their number, location and chirality is found to be independent on the detailed profile of the resolving space and to agree with the result of hep-th/0409229, in which a particular resolution was employed. As a consistency check of the resolution procedure, the massive equation is numerically studied. In particular, for S^1/Z_2, the "resolved" mass--spectrum and wave functions in the internal space are seen to correctly reproduce the usual orbifold ones, as the orbifold limit is taken.Comment: 28 pages, 3 figures, typos corrected, references adde

Role of availability of critical aquaculture inputs and community-managed markets on community-based floodplain wetland management

India has extensive wetlands of 2.02 lakh ha. These are basically low-lying floodplain areas. Assam has endowed huge floodplain wetlands and are locally called as Beel. These are one of the most important fishery resources of India providing livelihood to thousands of poor people. The average existing fish production of Assam Beel is only 173 kg/ha/year against its production potential of 1000-1500 kg/ ha/year. A study was conducted in three Beels of the Assam state to see the role of two situational independent variables namely availability of critical aquaculture inputs (X1) and community-managed markets (X2) on dependent variable i.e. knowledge levels of Beel users for community-based Beel fisheries management (Y). The study revealed that community-managed markets was significantly and positively associated (P<0.01) with knowledge levels of Beel users on community-based Beel fisheries management. Also, between these two variables, community managed market (X2) was found to be most significantly contributing variable (‘t’-value – 2.91**) on knowledge levels of Beel users for community-based Beel fisheries management (Y)

Evolving wormhole geometries

We present here analytical solutions of General Relativity that describe evolving wormholes with a non-constant redshift function. We show that the matter that threads these wormholes is not necessarily exotic. Finally, we investigate some issues concerning WEC violation and human traversability in these time-dependent geometries.Comment: 12 pages latex, 3 figures, to appear in Phys. Rev. D., Title correcte

Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC

We propose a new method to determine at what transverse momenta particle production in high-energy pp collisions is governed by hard parton-parton processes. Using information on the transverse spatial distribution of partons obtained from hard exclusive processes in ep/gamma p scattering, we evaluate the impact parameter distribution of pp collisions with a hard parton-parton process as a function of p_T of the produced parton (jet). We find that the average pp impact parameters in such events depend very weakly on p_T in the range 2 < p_T < few 100 GeV, while they are much smaller than those in minimum-bias inelastic collisions. The impact parameters in turn govern the observable transverse multiplicity in such events (in the direction perpendicular to the trigger particle or jet). Measuring the transverse multiplicity as a function of p_T thus provides an effective tool for determining the minimum p_T for which a given trigger particle originates from a hard parton-parton process. Additional tests of the proposed geometric correlations are possible by measuring the dependence on the trigger rapidity. Various strategies for implementing this method are outlined.Comment: 9 pages, 6 figure

Can degenerate bound states occur in one dimensional quantum mechanics?

We point out that bound states, degenerate in energy but differing in parity, may form in one dimensional quantum systems even if the potential is non-singular in any finite domain. Such potentials are necessarily unbounded from below at infinity and occur in several different contexts, such as in the study of localised states in brane-world scenarios. We describe how to construct large classes of such potentials and give explicit analytic expressions for the degenerate bound states. Some of these bound states occur above the potential maximum while some are below. Various unusual features of the bound states are described and after highlighting those that are ansatz independent, we suggest that it might be possible to observe such parity-paired degenerate bound states in specific mesoscopic systems.Comment: 10 pages, 2 figures, to appear in Europhysics Letter

Exact solutions in two-dimensional string cosmology with back reaction

We present analytic cosmological solutions in a model of two-dimensional dilaton gravity with back reaction. One of these solutions exhibits a graceful exit from the inflationary to the FRW phase and is nonsingular everywhere. A duality related second solution is found to exist only in the ``pre-big-bang'' epoch and is singular at $\tau = 0$. In either case back reaction is shown to play a crucial role in determining the specific nature of these geometries.Comment: Shortened slightly, references added, to appear in Physical Review D (Rapid Communications). 16 pages, RevTex, 3 PostScript figure