A counter-example to a recent version of the Penrose conjecture

By considering suitable axially symmetric slices on the Kruskal spacetime, we construct counterexamples to a recent version of the Penrose inequality in terms of so-called generalized apparent horizons.Comment: 12 pages. Appendix added with technical details. To appear in Classical and Quantum Gravit

Veneziano Amplitude for Winding Strings

String configurations with nonzero winding number describe soliton string states. We compute the Veneziano amplitude for the scattering of arbitrary winding states and show that in the large radius limit the strings always scatter trivially and with no change in the individual winding numbers of the strings. In this limit, then, these states scatter as true solitons.Comment: 7 page

Nonexistence of Generalized Apparent Horizons in Minkowski Space

We establish a Positive Mass Theorem for initial data sets of the Einstein equations having generalized trapped surface boundary. In particular we answer a question posed by R. Wald concerning the existence of generalized apparent horizons in Minkowski space

A Comment on String Solitons

We derive an exact string-like soliton solution of D=10 heterotic string theory. The solution possesses $SU(2)\times SU(2)$ instanton structure in the eight-dimensional space transverse to the worldsheet of the soliton.Comment: 4 page

String Solitons

We review the status of solitons in superstring theory, with a view to understanding the strong coupling regime. These {\it solitonic} solutions are non-singular field configurations which solve the empty-space low-energy field equations (generalized, whenever possible, to all orders in $\alpha'$), carry a non-vanishing topological "magnetic" charge and are stabilized by a topological conservation law. They are compared and contrasted with the {\it elementary} solutions which are singular solutions of the field equations with a $\sigma$-model source term and carry a non-vanishing Noether "electric" charge. In both cases, the solutions of most interest are those which preserve half the spacetime supersymmetries and saturate a Bogomol'nyi bound. They typically arise as the extreme mass=charge limit of more general two-parameter solutions with event horizons. We also describe the theory {\it dual} to the fundamental string for which the roles of elementary and soliton solutions are interchanged. In ten spacetime dimensions, this dual theory is a superfivebrane and this gives rise to a string/fivebrane duality conjecture according to which the fivebrane may be regarded as fundamental in its own right, with the strongly coupled string corresponding to the weakly coupled fivebrane and vice-versa. After compactification to four spacetime dimensions, the fivebrane appears as a magnetic monopole or a dual string according as it wraps around five or four of the compactified dimensions. This gives rise to a four-dimensional string/string duality conjecture which subsumes a Montonen-Olive type duality in that the magnetic monopoles of the fundamental string correspond to the electric winding states of the dual string. This leads to a {\it duality of dualities} whereby under string/string duality the the strong/weak coupling $S$-duality trades places with the minimum/maximum length $T$-duality. Since these magnetic monopoles are extreme black holes, a prediction of $S$-duality is that the corresponding electric massive states of the fundamental string are also extreme black holes.Comment: 150 pages, TeX, submitted to Physics Reports, 3 figures available on reques

Supersymmetry and Dual String Solitons

We present new classes of string-like soliton solutions in ($N=1$; $D=10$), ($N=2$; $D=6$) and ($N=4$; $D=4$) heterotic string theory. Connections are made between the solution-generating subgroup of the $T$-duality group of the compactification and the number of spacetime supersymmetries broken. Analogous solutions are also noted in ($N=1,2$; $D=4$) compactifications, where a different form of supersymmetry breaking arises.Comment: 13 pages, harvmac, (missing references added

Mitochondrial apoptosis induced by Chamaemelum nobile extract in breast cancer cells

Chamaemelum nobile (Asteraceae) commonly known as ‹Roman chamomile› is a medicinal plant used for numerous diseases in traditional medicine, although its anticancer activity is unknown. The present study was carried out to investigate the anticancer as well as apoptotic activity of ethyl acetate fraction of C. nobile on different cancerous cell lines. The cells were treated with varying concentrations (0.001-0.25 mg/mL) of this fraction for 24, 48 and 72 h. Apoptosis induced in MCF-7 cells following treatment with ethyl acetate fraction was measured using Annexin V/PI, flowcytometry and western blotting analysis. The results showed that C. nobile ethyl acetate fraction revealed relatively high antiproliferative activity on MCF-7 cells; however, it caused minimal growth inhibitory response in normal cells. The involvement of apoptosis as a major cause of the fraction-induced cell death was confirmed by annexin-V/PI assay. In addition, ethyl acetate fraction triggered the mitochondrial apoptotic pathway by decreasing the Bcl-2 as well as increasing of Bax protein expressions and subsequently increasing Bax/Bcl-2 ratio. Furthermore, decreased proliferation of MCF-7 cells in the presence of the fraction was associated with G2/M phase cell cycle arrest. These findings confirm that ethyl acetate fraction of C.nobile may contain a diversity of phytochemicals which suppress the proliferation of MCF-7 cells by inducing apoptosis. © 2016 by School of Pharmacy Shaheed Beheshti University of Medical Sciences and Health Services

Dynamics of Extreme Black Holes and Massive String States

In a recent paper, Duff and Rahmfeld argued that certain massive $N_R=1/2$ states of the four-dimensional heterotic string correspond to extreme black hole solutions. We provide further, dynamical, evidence for this identification by comparing the scattering of these elementary string states with that of the corresponding extreme black holes, in the limit of low velocities.Comment: 18 pages, harvma

Brane Effects on Extra Dimensional Scenarios: A Tale of Two Gravitons

We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four dimensional brane located in a (nearly) flat extra dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions and a physical ultraviolet cutoff of the order of the fundamental Planck scale in the higher dimensional theory. We show that, contrary to recent suggestions, the radius of the extra dimensions cannot be arbitrarily large. Moreover, for finite radii, the gravitational effects localized on the brane can substantially alter the phenomenology of collider and/or table-top gravitational experiments. This phenomenology is dictated by the presence of a massless graviton, with standard couplings to the matter fields, and a massive graviton which couples to matter in a much stronger way. While graviton KK modes lighter than the massive graviton couple to matter in a standard way, the couplings to matter of the heavier KK modes are strongly suppressed.Comment: 21 pages, latex2e, axodraw.sty, 2 figure