Black Hole Emission in String Theory and the String Phase of Black Holes

String theory properly describes black-hole evaporation. The quantum string emission by Black Holes is computed. The black-hole temperature is the Hawking temperature in the semiclassical quantum field theory (QFT) regime and becomes the intrinsic string temperature, T_s, in the quantum (last stage) string regime. The QFT-Hawking temperature T_H is upper bounded by the string temperature T_S. The black hole emission spectrum is an incomplete gamma function of (T_H - T_S). For T_H << T_S, it yields the QFT-Hawking emission. For T_H \to T_S, it shows highly massive string states dominate the emission and undergo a typical string phase transition to a microscopic `minimal' black hole of mass M_{\min} or radius r_{\min} (inversely proportional to T_S) and string temperature T_S. The string back reaction effect (selfconsistent black hole solution of the semiclassical Einstein equations) is computed. Both, the QFT and string black hole regimes are well defined and bounded.The string `minimal' black hole has a life time tau_{min} simeq (k_B c)/(G hbar [T_S]^3). The semiclassical QFT black hole (of mass M and temperature T_H) and the string black hole (of mass M_{min} and temperature T_S) are mapped one into another by a `Dual' transform which links classical/QFT and quantum string regimes.Comment: LaTex, 22 pages, Lectures delivered at the Chalonge School, Nato ASI: Phase Transitions in the Early Universe: Theory and Observations. To appear in the Proceedings, Editors H. J. de Vega, I. Khalatnikov, N. Sanchez. (Kluwer Pub

Accurate energy spectrum for double-well potential: periodic basis

We present a variational study of employing the trigonometric basis functions satisfying periodic boundary condition for the accurate calculation of eigenvalues and eigenfunctions of quartic double-well oscillators. Contrary to usual Dirichlet boundary condition, imposing periodic boundary condition on the basis functions results in the existence of an inflection point with vanishing curvature in the graph of the energy versus the domain of the variable. We show that this boundary condition results in a higher accuracy in comparison to Dirichlet boundary condition. This is due to the fact that the periodic basis functions are not necessarily forced to vanish at the boundaries and can properly fit themselves to the exact solutions.Comment: 15 pages, 5 figures, to appear in Molecular Physic

The Spin Structure of the Nucleon

We present an overview of recent experimental and theoretical advances in our understanding of the spin structure of protons and neutrons.Comment: 84 pages, 29 figure

Light-Cone Quantization and Hadron Structure

In this talk, I review the use of the light-cone Fock expansion as a tractable and consistent description of relativistic many-body systems and bound states in quantum field theory and as a frame-independent representation of the physics of the QCD parton model. Nonperturbative methods for computing the spectrum and LC wavefunctions are briefly discussed. The light-cone Fock state representation of hadrons also describes quantum fluctuations containing intrinsic gluons, strangeness, and charm, and, in the case of nuclei, "hidden color". Fock state components of hadrons with small transverse size, such as those which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions; i.e., "color transparency". The use of light-cone Fock methods to compute loop amplitudes is illustrated by the example of the electron anomalous moment in QED. In other applications, such as the computation of the axial, magnetic, and quadrupole moments of light nuclei, the QCD relativistic Fock state description provides new insights which go well beyond the usual assumptions of traditional hadronic and nuclear physics.Comment: LaTex 36 pages, 3 figures. To obtain a copy, send e-mail to [email protected]

The asymptotic behaviour of parton distributions at small and large xx

It has been argued from the earliest days of quantum chromodynamics that at asymptotically small values of x the parton distribution functions (PDFs) of the proton behave as xαxα, where the values of αα can be deduced from Regge theory, while at asymptotically large values of x the PDFs behave as (1−x)β(1−x)β, where the values of ββ can be deduced from the Brodsky–Farrar quark counting rules. We critically examine these claims by extracting the exponents αα and ββ from various global fits of parton distributions, analysing their scale dependence, and comparing their values to the naive expectations. We find that for valence distributions both Regge theory and counting rules are confirmed, at least within uncertainties, while for sea quarks and gluons the results are less conclusive. We also compare results from various PDF fits for the structure function ratio Fn2/Fp2F2n/F2p at large x, and caution against unrealistic uncertainty estimates due to overconstrained parametrisations

Leptonic Production of Baryon Resonances

In these lectures, the author focuses on the electromagnetic transition between non-strange baryon states. This sector received much attention in the early 1970's after the development of the first dynamical quark models. However, experimental progress was slow, partly because of the low rates associated with electromagnetic interactions, and partly because of the lack of guidance by theoretical models that went beyond the simplest quark models. It was also difficult for experiments to achieve the precision needed for a detailed analysis of the entire resonance region in terms of the fundamental photocoupling amplitudes over a large range in momentum transfer

Proceedings of the 24th International Stroke Genetics Consortium Workshop: Washington, DC, USA

Objective: To identify haematological traits with a causal role in the development of stroke and stroke subtypes. Background: Blood cells and coagulation factors have many important roles including oxygen transport, immune response, iron homeostasis, clearance of apoptotic cells and toxins, vascular and endothelial cell function, response to systemic stress, and haemostasis. A recent analysis found evidence of a causal effect of several blood cell traits on coronary heart disease and Type 2 diabetes, but the causal relevance of haematological traits for stroke and its subtypes has not been established. This information is critical to inform the development of novel treatments for stroke patients. Design/Methods: We conducted a literature review of genome-wide association studies of haematological traits and downloaded publicly available summary statistics from these studies and the MEGASTROKE consortium. Mendelian randomization analyses were used to examine whether haematological traits have a causal effect on the development of stroke and its subtypes in both European-only and trans-ethnic populations. A gene score constructed from independent genetic variants associated with each trait was used as an instrumental variable to obtain an estimate of the causal effect using the ratio, inverse-variance weighted, weighted median, and MR-Egger approaches. Results: The literature review identified 36 blood cell traits (platelets, mature/immature red cells, and myeloid/lymphoid/compound white cells), 43 coagulation factors, and 3 markers of platelet function from 28 published GWAS, which included data from UK Biobank, INTERVAL, CHARGE Consortium, CARe Consortium, BioBank Japan Project, ARIC, Rotterdam Study, Framingham Heart Study, and other cohorts, involving over 350,000 individuals. Genetic associations with stroke and stroke subtypes were available in 67,162 cases and 454,450 controls. Preliminary analyses on a subset of traits showed that plateletcrit had a significant causal effect (p < 8.4746 × 10−4) on all stroke (AS), any ischaemic stroke (AIS), and cardioembolic stroke (CES) in both European-only and trans-ethnic populations; Factor VIII activity had a significant causal effect on AS, AIS, large-artery stroke (LAS), and CES in both populations; and von Willebrand Factor had a significant causal effect on AS and AIS in both populations and a marginally significant effect (p < 1 × 10−3) on CES in a trans-ethnic population. There were also suggestive causal associations of 27 of the blood cell traits on stroke and various subtypes; of activated partial thromboplastin time and Factor VII clotting activity with AS, AIS, and small vessel stroke (SVS); and of prothrombin time and collagen lag time with CES. Conclusions: Our preliminary analyses have so far identified one blood cell trait, 2 coagulation factors, and one marker of platelet function that exhibit evidence of a significant causal association with stroke and various subtypes of stroke, as well as numerous haematological traits that are marginally significant or suggestive of a causal effect. Further investigation of these traits could lead to the development of novel drug targets for the treatment and prevention of stroke.EU Horizon 2020 grant agreement No 667375 (CoSTREAM