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

More on Four-Dimensional Extremal Black Holes

We consider an embedding of the extremal four-dimensional Reissner-Nordstr\"om black hole into type $IIB$ string theory. The equivalent type $IIB$ configuration, in the D-brane weak-coupling picture, is a bound state of D1- and D5-branes threaded by fundamental type $IIB$ strings. The bound state involves also a NSNS solitonic 5-brane, mimicking the role of the Kaluza-Klein magnetic monopole. The statistical entropy derived by counting the degeneracy of the BPS-saturated excitations of this bound state agrees perfectly with the (semiclassical) Bekenstein-Hawking formula.Comment: 19 pages, using Latex, no figure

Total Widths And Slopes From Complex Regge Trajectories

Maximally complex Regge trajectories are introduced for which both Re $\alpha(s)$ and Im $\alpha(s)$ grow as $s^{1-\epsilon}$ ($\epsilon$ small and positive). Our expression reduces to the standard real linear form as the imaginary part (proportional to $\epsilon$) goes to zero. A scaling formula for the total widths emerges: $\Gamma_{TOT}/M\to$ constant for large M, in very good agreement with data for mesons and baryons. The unitarity corrections also enhance the space-like slopes from their time-like values, thereby resolving an old problem with the $\rho$ trajectory in $\pi N$ charge exchange. Finally, the unitarily enhanced intercept, $\alpha_{\rho}\approx 0.525$, \nolinebreak is in good accord with the Donnachie-Landshoff total cross section analysis.Comment: 9 pages, 3 Figure

Synthetic Retinoid Interventions and Outcomes in People with Cancer or Potentially Malignant Disorders of the Upper Aerodigestive Tract: A Systematic Review and Meta-analysis

Background & Aims: Retinoids may have a role in the chemoprevention of potentially malignant disorders of the upper aerodigestive tract. Therefore, we conducted a systematic review of randomised controlled trials to examine the effect of synthetic retinoid interventions in people with cancer or potentially malignant disorders of the upper digestive tract. Methods: We searched five electronic databases and reference lists to locate all eligible trials and analysed trial quality. Outcome measures were all-cause and cancer mortality, disease-free survival, second primary cancer, cancer and potentially malignant disorder recurrence and progression to cancer. Results of individual trials were combined by use of random-effects meta-analyses. Results & Conclusions: We identified 17 15 trials, eightnine in people with upper aerodigestive tract cancer and seven eight in people with potentially malignant disorders, respectively. The results provide little evidence that retinoids have a beneficial effect on disease-free survival (OR=0.74, 95% CI =0.51, 1.09), all cause mortality (OR = 1.28, 95% confidence interval [CI] =1.00 to 1.65), disease-free survival (OR=0.74, 95% CI =0.51, 1.09), recurrence of cancer (OR = 1.47, 95% CI = 0.95, 2.26), development of second primary cancers (OR = 0.96, 95% CI = 0.76, 1.20) or the progression to malignancy (OR = 0.69, 95% CIs = 0.22, 2.15). There was even a suggestion of harm for some outcomes. There was also a suggestion that retinoids may decrease the recurrence of potentially malignant disorders (OR = 0.22, 95% CIs = 0.03, 1.34). For now there is no evidence to support the use of retinoids in people with upper aerodigestive tract cancer

Monopoles and Instantons in String Theory

In recent work, several classes of solitonic solutions of string theory with higher-membrane structure have been obtained. These solutions can be classified according to the symmetry possessed by the solitons in the subspace of the spacetime transverse to the membrane. Solitons with four-dimensional spherical symmetry represent instanton solutions in string theory, while those with three-dimensional spherical symmetry represent magnetic monopole-type solutions. For both of these classes, we discuss bosonic as well as heterotic solutions.Comment: 16 page

Nucleation of PP-Branes and Fundamental Strings

We construct a solution to the low-energy string equations of motion in five dimensions that describes a circular loop of fundamental string exponentially expanding in a background electric $H$-field. Euclideanising this gives an instanton for the creation of a loop of fundamental string in a background $H$-field, and we calculate the rate of nucleation. Solutions describing magnetically charged strings and $p$-branes, where the gauge field comes from Kaluza-Klein reduction on a circle, are also constructed. It is known that a magnetic flux tube in four (reduced) spacetime dimensions is unstable to the pair creation of Kaluza-Klein monopoles. We show that in $(4+p)$ dimensions, magnetic $(p+1)$ ``fluxbranes" are unstable to the nucleation of a magnetically charged spherical $p$-brane. In ten dimensions the instanton describes the nucleation of a Ramond-Ramond magnetically charged six-brane in type IIA string theory. We also find static solutions describing spherical charged $p$-branes or fundamental strings held in unstable equilibrium in appropriate background fields. Instabilities of intersecting magnetic fluxbranes are also discussed.Comment: 28 pages, harvmac (b), reference added, typos correcte

A compactness theorem for scalar-flat metrics on manifolds with boundary

Let (M,g) be a compact Riemannian manifold with boundary. This paper is concerned with the set of scalar-flat metrics which are in the conformal class of g and have the boundary as a constant mean curvature hypersurface. We prove that this set is compact for dimensions greater than or equal to 7 under the generic condition that the trace-free 2nd fundamental form of the boundary is nonzero everywhere.Comment: 49 pages. Final version, to appear in Calc. Var. Partial Differential Equation

The extremal black holes of N=4 supergravity from so(8,2+n) nilpotent orbits

We consider the stationary solutions of N=4 supergravity coupled to n vector multiplets that define linear superpositions of non-interacting extremal black holes. The most general solutions of this type are derived from the graded decompositions of so(8,2+n) associated to its nilpotent orbits. We illustrate the formalism by giving explicitly asymptotically Minkowski non-BPS solutions of the most exotic class depending on 6+n harmonic functions.Comment: Corrected version for publication, references adde

Measurement of the η→3π0\eta\to 3\pi^{0} slope parameter α\alpha with the KLOE detector

We present a measurement of the slope parameter $\alpha$ for the $\eta\to 3\pi^{0}$ decay, with the KLOE experiment at the DA$\Phi$NE $\phi$-factory, based on a background free sample of $\sim$ 17 millions $\eta$ mesons produced in $\phi$ radiative decays. By fitting the event density in the Dalitz plot we determine \alpha = -0.0301 \pm 0.0035\,stat\;_{-0.0035}^{+0.0022}\,syst\,. The result is in agreement with recent measurements from hadro- and photo-production experiments.Comment: 14 pages, 11 figure

Sect and House in Syria: History, Architecture, and Bayt Amongst the Druze in Jaramana

This paper explores the connections between the architecture and materiality of houses and the social idiom of bayt (house, family). The ethnographic exploration is located in the Druze village of Jaramana, on the outskirts of the Syrian capital Damascus. It traces the histories, genealogies, and politics of two families, bayt Abud-Haddad and bayt Ouward, through their houses. By exploring the two families and the architecture of their houses, this paper provides a detailed ethnographic account of historical change in modern Syria, internal diversity, and stratification within the intimate social fabric of the Druze neighbourhood at a time of war, and contributes a relational approach to the anthropological understanding of houses