The effect of metapopulation processes on the spatial scale of adaptation across an environmental gradient

We show that the butterfly Aricia agestis (Lycaenidae) is adapted to its thermal environment in via integer changes in the numbers of generations per year (voltinism): it has two generations per year in warm habitats and one generation per year in cool habitats in north Wales (UK). Voltinism is an “adaptive peak” since individuals having an intermediate number of generations per year would fail to survive the winter, and indeed no populations showed both voltinism types in nature. In spite of this general pattern, 11% of populations apparently possess the “wrong” voltinism for their local environment, and population densities were lower in thermally intermediate habitat patches. Population dynamic data and patterns of genetic differentiation suggest that adaptation occurs at the metapopulation level, with local populations possessing the voltinism type appropriate for the commonest habitat type within each population network. When populations and groups of populations go extinct, they tend to be replaced by colonists from the commonest thermal environment nearby, even if this is the locally incorrect adaptation. Our results illustrate how stochastic population turnover can impose a limit on local adaptation over distances many times larger than predicted on the basis of normal dispersal movements

String Necklaces and Primordial Black Holes from Type IIB Strings

We consider a model of static cosmic string loops in type IIB string theory, where the strings wrap cycles within the internal space. The strings are not topologically stabilised, however the presence of a lifting potential traps the windings giving rise to kinky cycloops. We find that PBH formation occurs at early times in a small window, whilst at late times we observe the formation of dark matter relics in the scaling regime. This is in stark contrast to previous predictions based on field theoretic models. We also consider the PBH contribution to the mass density of the universe, and use the experimental data to impose bounds on the string theory parameters.Comment: 45 pages, 9 figures, LaTeX; published versio

Effective Actions near Singularities

We study the heterotic string compactified on K3 x T^2 near the line T=U, where the effective action becomes singular due to an SU(2) gauge symmetry enhancement. By `integrating in' the light W^\pm vector multiplets we derive a quantum corrected effective action which is manifestly SU(2) invariant and non-singular. This effective action is found to be consistent with a residual SL(2,Z) quantum symmetry on the line T=U. In an appropriate decompactification limit, we recover the known SU(2) invariant action in five dimensions.Comment: 33 pages, LaTeX. v2: cosmetic correction on titlepage. v3: references and note adde

Non-Abelian (p,q) Strings in the Warped Deformed Conifold

We calculate the tension of $(p,q)$-strings in the warped deformed conifold using the non-Abelian DBI action. In the large flux limit, we find exact agreement with the recent expression obtained by Firouzjahi, Leblond and Henry-Tye up to and including order $1/M^2$ terms if $q$ is also taken to be large. Furthermore using the finite $q$ prescription for the symmetrised trace operation we anticipate the most general expression for the tension valid for any $(p,q)$. We find that even in this instance, corrections to the tension scale as $1/M^2$ which is not consistent with simple Casimir scaling.Comment: 18 pages, Latex, 1 figure; Added a discussion of the case when the warp factor parameter $b\neq 1$ and typos correcte

Dielectric (p,q) Strings in a Throat

We calculate the (p,q) string spectrum in a warped deformed conifold using the dielectric brane method. The spectrum is shown to have the same functional form as in the dual picture of a wrapped D3-brane with electric and magnetic fluxes on its world volume. The agreement is exact in the limit where q is large. We also calculate the dielectric spectrum in the S-dual picture. The spectrum in the S-dual picture has the same form as in the original picture but it is not exactly S-dual invariant due to an interchange of Casimirs of the non-Abelian gauge symmetries. We argue that in order to restore S-duality invariance the non-Abelian brane action should be refined, probably by a better prescription for the non-Abelian trace operation

Pressure-Temperature Phase Diagram of Antiferromagnetism and Superconductivity in CeRhIn5 and CeIn3 : In-NQR Study under Pressure

We report the novel pressure($P$) - temperature($T$) phase diagram of antiferromagnetism and superconductivity in CeRhIn$_5$ and CeIn$_3$ revealed by the $^{115}$In nuclear-spin-lattice-relaxation ($T_1$) measurement. In the itinerant magnet CeRhIn$_5$, we found that the N\'eel temperature $T_N$ is reduced at $P \geq$ 1.23 GPa with an emergent pseudogap behavior. In CeIn$_3$, the localized magnetic character is robust against the application of pressure up to $P \sim$ 1.9 GPa, beyond which the system evolves into an itinerant regime in which the resistive superconducting phase emerges. We discuss the relationship between the phase diagram and the magnetic fluctuations.Comment: 4 pages, 3 figures, to be published in Phys.Rev.B. Rapid

D-Brane Propagation in Two-Dimensional Black Hole Geometries

We study propagation of D0-brane in two-dimensional Lorentzian black hole backgrounds by the method of boundary conformal field theory of SL(2,R)/U(1) supercoset at level k. Typically, such backgrounds arise as near-horizon geometries of k coincident non-extremal NS5-branes, where 1/k measures curvature of the backgrounds in string unit and hence size of string worldsheet effects. At classical level, string worldsheet effects are suppressed and D0-brane propagation in the Lorentzian black hole geometry is simply given by the Wick rotation of D1-brane contour in the Euclidean black hole geometry. Taking account of string worldsheet effects, boundary state of the Lorentzian D0-brane is formally constructible via Wick rotation from that of the Euclidean D1-brane. However, the construction is subject to ambiguities in boundary conditions. We propose exact boundary states describing the D0-brane, and clarify physical interpretations of various boundary states constructed from different boundary conditions. As it falls into the black hole, the D0-brane radiates off to the horizon and to the infinity. From the boundary states constructed, we compute physical observables of such radiative process. We find that part of the radiation to infinity is in effective thermal distribution at the Hawking temperature. We also find that part of the radiation to horizon is in the Hagedorn distribution, dominated by massive, highly non-relativistic closed string states, much like the tachyon matter. Remarkably, such distribution emerges only after string worldsheet effects are taken exactly into account. From these results, we observe that nature of the radiation distribution changes dramatically across the conifold geometry k=1 (k=3 for the bosonic case), exposing the `string - black hole transition' therein.Comment: 51 pages, 5 figures, v2: referece added, note added replying the comment made in hep-th/060206

Open String Attractors

We present a simple example of a supersymmetric attractor mechanism in the purely open string context of D-branes embedded in curved space-time. Our example involves a class of D3-branes embedded in the 2-charge D1-D5 background of type IIB whose worldvolume contains a 2-sphere. Turning on worldvolume fluxes, these branes carry induced (p,q) string charges. Supersymmetric configurations display a flow of the open string moduli towards an attractor solution independent of their asymptotics. The equations governing this mechanism closely resemble the attractor flow equations for supersymmetric black holes in closed string theory. The BPS equations take the form of a gradient flow and describe worldvolume solitons interpolating between an AdS_2 geometry where the two-sphere has collapsed, and an attractor solution with AdS_2 x S^2 geometry. In these limiting solutions, the preserved supersymmetry is enhanced from 4 to 8 supercharges. We also discuss the interpretation of our solutions as intersecting brane configurations placed in the D1-D5 background, as well as the S-duality transformation to the F1-NS5 background.Comment: 37 pages, 6 figures. v2: small corrections, figure and references adde

Negative Energy in String Theory and Cosmic Censorship Violation

We find asymptotically anti de Sitter solutions in N=8 supergravity which have negative total energy. This is possible since the boundary conditions required for the positive energy theorem are stronger than those required for finite mass (and allowed by string theory). But stability of the anti de Sitter vacuum is still ensured by the positivity of a modified energy, which includes an extra surface term. Some of the negative energy solutions describe classical evolution of nonsingular initial data to naked singularities. Since there is an open set of such solutions, cosmic censorship is violated generically in supergravity. Using the dual field theory description, we argue that these naked singularities will be resolved in the full string theory.Comment: 23 pages, 2 figures, v2: argument for forming naked singularities clarified, references adde

Determination of pi-N scattering lengths from pionic hydrogen and pionic deuterium data

The pi-N s-wave scattering lengths have been inferred from a joint analysis of the pionic hydrogen and the pionic deuterium x-ray data using a non-relativistic approach in which the pi-N interaction is simulated by a short-ranged potential. The pi-d scattering length has been calculated exactly by solving the Faddeev equations and also by using a static approximation. It has been shown that the same very accurate static formula for pi-d scattering length can be derived (i) from a set of boundary conditions; (ii) by a reduction of Faddeev equations; and (iii) through a summation of Feynman diagrams. By imposing the requirement that the pi-d scattering length, resulting from Faddeev-type calculation, be in agreement with pionic deuterium data, we obtain bounds on the pi-N scattering lengths. The dominant source of uncertainty on the deduced values of the pi-N scattering lengths are the experimental errors in the pionic hydrogen data.Comment: RevTeX, 20 pages,4 PostScript figure