Quasilocal Energy for a Kerr black hole

The quasilocal energy associated with a constant stationary time slice of the Kerr spacetime is presented. The calculations are based on a recent proposal \cite{by} in which quasilocal energy is derived from the Hamiltonian of spatially bounded gravitational systems. Three different classes of boundary surfaces for the Kerr slice are considered (constant radius surfaces, round spheres, and the ergosurface). Their embeddings in both the Kerr slice and flat three-dimensional space (required as a normalization of the energy) are analyzed. The energy contained within each surface is explicitly calculated in the slow rotation regime and its properties discussed in detail. The energy is a positive, monotonically decreasing function of the boundary surface radius. It approaches the Arnowitt-Deser-Misner (ADM) mass at spatial infinity and reduces to (twice) the irreducible mass at the horizon of the Kerr black hole. The expressions possess the correct static limit and include negative contributions due to gravitational binding. The energy at the ergosurface is compared with the energies at other surfaces. Finally, the difficulties involved in an estimation of the energy in the fast rotation regime are discussed.Comment: 22 pages, Revtex, Alberta-Thy-18-94. (the approximations in Section IV have been improved. To appear in Phys. Rev. D

Competing With the NYSE

We study the stock exchange rivalry between the New York Stock Exchange (NYSE) and the Consolidated Stock Exchange (Consolidated) from 1885 to 1926 using a new database of bid-ask spreads and stock data collected from The New York Times and other primary sources. The magnitude of this important, but largely forgotten rivalry was substantial. From 1885 to 1895, the ratio of Consolidated to NYSE volume averaged 40 percent and reached as high as 60 percent. The market share of the Consolidated averaged 23 percent for approximately 40 years. The Consolidated focused on the relatively liquid securities on the NYSE as measured by bid-ask spreads and trading volume. Our results suggest that NYSE bid-ask spreads fell by more than 10 percent when the Consolidated began to trade NYSE stocks while bid-ask spreads for our quasicontrol group of stocks trading on the Boston Stock Exchange remain unchanged. The effect persisted over the entire history of the stock market rivalry until a series of scandals and investigations of the Consolidated by state regulators led to the demise of the exchange in the 1920s. The analysis suggests three conclusions: (1) the NYSE has faced significant long-run competition (2) the NYSE may be susceptible to a similar level of competition in the future and (3) that the Consolidated may have improved the efficiency of stock prices by contributing to the price discovery process.

Viral gastrointestinal infections and norovirus genotypes in a paediatric UK hospital, 2014-2015

BACKGROUND: Diarrhoea in children is a common disease; understanding the incidence of causative viruses can aid infection control and vaccine development. OBJECTIVES: Describe the incidence and characteristics of gastroenteric viruses including norovirus genotypes in a paediatric hospital cohort. STUDY DESIGN: Norovirus, adenovirus, sapovirus, astrovirus, rotavirus qPCR and norovirus genotyping results for all stool specimens (n = 4786; 1393 patients) at a UK paediatric tertiary referral hospital June 2014–July 2015. RESULTS AND DISCUSSION: 24% (329/1393) of patients were positive for a GI virus; the majority were positive for norovirus (44%, 144/329) or adenovirus (44%, 146/329). The overall incidence of rotavirus (2%) is reduced compared to pre-vaccination studies; however the incidence of other GI viruses has not increased. Norovirus infections had a significantly higher virus burden compared to other GI viruses (P ≤0.03); sapovirus infections had the lowest viral burden. The number of norovirus cases per month did not follow the typical winter seasonal trend of nationally reported outbreaks. The number of cases per month correlates with the number of hospital admissions (R = 0.703, P = 0.011); the number of admissions accounts for 50% of the variability in number of cases per month. The breadth of genotypes seen (48% non-GII.4), suggests a community source for many norovirus infections and has implications for vaccine development. All GI viruses caused chronic infections, with the majority (50–100%) in immunocompromised patients. Incidence or duration of infection in chronic norovirus infections did not differ between genotypes, suggesting host-mediated susceptibility

Development of Replacement Heifers using Combinations of Three Forage Types and Feed Supplements (with or without Broiler Litter)

The proper management of replacement heifers is an essential component of successful cow/calf operations. The level of management and nutrition applied to replacement heifers as calves and yearlings can impact their subsequent reproductive performance and productivity

Analytical study of a free-wing/free-trimmer concept

The free-wing/free-trimmer is a NASA-Conceived extension of the free-wing concept intended to permit the use of high-lift flaps. Wing pitching moments are balanced by a smaller, external surface attached by a boom or equivalent structure. The external trimmer is, itself, a miniature free wing, and pitch control of the wing-trimmer assembly is effected through a trailing-edge control tab on the trimmer surface. The longitudinal behavior of representative small free-wing/free-trimmer aircraft was analyzed. Aft-mounted trimmer surfaces are found to be superior to forward trimmers, although the permissible trimmer moment arm is limited, in both cases, by adverse dynamic effects. Aft-trimmer configurations provide excellent gust alleviation and meet fundamental stick-fixed stability criteria while exceeding the lift capabilities of pure free-wing configurations

Cosmological Supergravity from a Massive Superparticle and Super Cosmological Black Holes

We describe in superspace a classical theory of two dimensional $(1,1)$ dilaton supergravity with a cosmological constant, both with and without coupling to a massive superparticle. We give general exact non-trivial superspace solutions for the compensator superfield that describes the supergravity in both cases. We then use these compensator solutions to construct models of two-dimensional supersymmetric cosmological black holes.Comment: 20 pages, Late

Free Energy and Entropy for Semi-classical Black Holes in the Canonical Ensemble

We consider the thermodynamics of a black hole coupled to thermal radiation in a spatially finite (spherical) region. Thermodynamic state functions are derived in the canonical ensemble, defined by elements of radius $r_o$ and boundary temperature $T(r_o)$. Using recent solutions of the semi-classical back reaction problem, we compute the $O(\hbar)$ corrections to the mass of the black hole, thermal energy, the entropy and free energy due to the presence of hot conformal scalars, massless spinors and U(1) gauge quantum fields in the vicinity of the hole. The free energy is particularly important for assessing under what conditions the nucleation of black holes from hot flat space is likely to occur.Comment: 25 pages, not including 10 Figures available upon request from the author: LAEFF-94/08. Typed in LaTe

The postulates of gravitational thermodynamics

The general principles and logical structure of a thermodynamic formalism that incorporates strongly self-gravitating systems are presented. This framework generalizes and simplifies the formulation of thermodynamics developed by Callen. The definition of extensive variables, the homogeneity properties of intensive parameters, and the fundamental problem of gravitational thermodynamics are discussed in detail. In particular, extensive parameters include quasilocal quantities and are naturally incorporated into a set of basic general postulates for thermodynamics. These include additivity of entropies (Massieu functions) and the generalized second law. Fundamental equations are no longer homogeneous first-order functions of their extensive variables. It is shown that the postulates lead to a formal resolution of the fundamental problem despite non-additivity of extensive parameters and thermodynamic potentials. Therefore, all the results of (gravitational) thermodynamics are an outgrowth of these postulates. The origin and nature of the differences with ordinary thermodynamics are analyzed. Consequences of the formalism include the (spatially) inhomogeneous character of thermodynamic equilibrium states, a reformulation of the Euler equation, and the absence of a Gibbs-Duhem relation.Comment: 28 pages, Revtex, no figures. An important sentence and several minor corrections included. To appear in Physical Review

Microstructural strain energy of α-uranium determined by calorimetry and neutron diffractometry

The microstructural contribution to the heat capacity of α-uranium was determined by measuring the heat-capacity difference between polycrystalline and single-crystal samples from 77 to 320 K. When cooled to 77 K and then heated to about 280 K, the uranium microstructure released (3±1) J/mol of strain energy. On further heating to 300 K, the microstructure absorbed energy as it began to redevelop microstrains. Anisotropic strain-broadening parameters were extracted from neutron-diffraction measurements on polycrystals. Combining the strain-broadening parameters with anisotropic elastic constants from the literature, the microstructural strain energy is predicted in the two limiting cases of statistically isotropic stress and statistically isotropic strain. The result calculated in the limit of statistically isotropic stress was (3.7±0.5) J/mol K at 77 K and (1±0.5) J/mol at room temperature. In the limit of statistically isotropic strain, the values were (7.8±0.5) J/mol K at 77 K and (4.5±0.5) J/mol at room temperature. In both cases the changes in the microstructural strain energy showed good agreement with the calorimetry

Spin Transfer Torque for Continuously Variable Magnetization

We report quantum and semi-classical calculations of spin current and spin-transfer torque in a free-electron Stoner model for systems where the magnetization varies continuously in one dimension.Analytic results are obtained for an infinite spin spiral and numerical results are obtained for realistic domain wall profiles. The adiabatic limit describes conduction electron spins that follow the sum of the exchange field and an effective, velocity-dependent field produced by the gradient of the magnetization in the wall. Non-adiabatic effects arise for short domain walls but their magnitude decreases exponentially as the wall width increases. Our results cast doubt on the existence of a recently proposed non-adiabatic contribution to the spin-transfer torque due to spin flip scattering.Comment: 11 pages, 9 figure