Energy in Topologically Massive Gravity

We define conserved gravitational charges in -cosmologically extended- topologically massive gravity, exhibit them in surface integral form about their de-Sitter or flat vacua and verify their correctness in terms of two basic types of solution.Comment: 6 page

Gravitating Instantons In 3 Dimensions

We study the Einstein-Chern-Simons gravity coupled to Yang-Mills-Higgs theory in three dimensional Euclidean space with cosmological constant. The classical equations reduce to Bogomol'nyi type first order equations in curved space. There are BPS type gauge theory instanton (monopole) solutions of finite action in a gravitational instanton which itself has a finite action. We also discuss gauge theory instantons in the vacuum (zero action) AdS space. In addition we point out to some exact solutions which are singular.Comment: 17 pages, 4 figures, title has changed, gravitational instanton actions are adde

Strong Secrecy for Multiple Access Channels

We show strongly secret achievable rate regions for two different wiretap multiple-access channel coding problems. In the first problem, each encoder has a private message and both together have a common message to transmit. The encoders have entropy-limited access to common randomness. If no common randomness is available, then the achievable region derived here does not allow for the secret transmission of a common message. The second coding problem assumes that the encoders do not have a common message nor access to common randomness. However, they may have a conferencing link over which they may iteratively exchange rate-limited information. This can be used to form a common message and common randomness to reduce the second coding problem to the first one. We give the example of a channel where the achievable region equals zero without conferencing or common randomness and where conferencing establishes the possibility of secret message transmission. Both coding problems describe practically relevant networks which need to be secured against eavesdropping attacks.Comment: 55 page

Coronary arterial anomalies in a large group of patients undergoing coronary angiography in southeast Turkey

Background: The prevalence of coronary artery anomalies (CAA) are reportedbetween 0.6–1.3% in the literature. CAA are usually asymptomatic incidental findings, but they may deteriorate coronary circulation, cause symptoms andlead to sudden cardiac death; especially in young athletes. Since interventionalprocedures are increasing rapidly for treatment of coronary artery disease (CAD) inthe modern era, comprehensive understanding of CAA is becoming progressively critical element in dealing with CAD.Materials and methods: We reviewed the database of the Cardiac Catheterisation Laboratory of Sani Konukoglu University Hospital in Gaziantep, Turkey. All patientswho were subjected to coronary angiography from 1998 to 2006 were included.Results: Among 53,655 coronary angiographies performed, CAA were foundin 653 patients (incidence of 1.21%); 590 (90.3%) patients had anomalies oforigin and distribution and 63 (11.7%) had coronary fistulae. Separate origins ofleft anterior descending (LAD) and left circumflex (LCX) coronary artery from theleft sinus of Valsalva was the most common anomaly (64.1%). Coronary arteriesbranching from anomalous aortic origin was the second most common anomaly(16.5%). Right coronary artery (RCA) originating from left sinus of Valsalva or leftmain coronary artery (LMCA) was observed in 55 (8.4%) patients, LCX arising fromRCA or right sinus of Valsalva (RSV) was seen in 52 (7.9%) patients and LMCA orLAD originating from RSV was seen in 14 (0.2%) patients. There were 16 (2.45%) patients with single coronary artery and 1 (0.15%) patient with LMCA originating from pulmonary artery.Conclusions: The incidence and the pattern of CAA in our patient population were similar with previous studies. Angiographic recognition of these vessels is importantbecause of their clinical significance and importance in patients undergoing coronary angioplasty or cardiac surgery

A comprehensive study of the energy absorption and exposure buildup factors of different bricks for gamma-rays shielding

The present investigation has been performed on different bricks for the purpose of gamma-ray shielding. The values of the mass attenuation coefficient (µ/ρ), energy absorption buildup factor (EABF) and exposure buildup factor (EBF) were determined and utilized to assess the shielding effectiveness of the bricks under investigation. The mass attenuation coefficients of the selected bricks were calculated theoretically using WinXcom program and compared with MCNPX code. Good agreement between WinXcom and MCNPX results was observed. Furthermore, the EABF and EBF have been discussed as functions of the incident photon energy and penetration depth. It has been found that the EABF and EBF values are very large in the intermediate energy region. The steel slag showed good shielding properties, consequently, this brick is eco-friendly and feasible compared with other types of bricks used for construction. The results in this work should be useful in the construction of effectual shielding against hazardous gamma-rays

Effective Lagrangian from Higher Curvature Terms: Absence of vDVZ Discontinuity in AdS Space

We argue that the van Dam-Veltman-Zakharov discontinuity arising in the $M^2 \to 0$ limit of the massive graviton through an explicit Pauli-Fierz mass term could be absent in anti de Sitter space. This is possible if the graviton can acquire mass spontaneously from the higher curvature terms or/and the massless limit $M^2\to 0$ is attained faster than the cosmological constant $\Lambda \to 0$. We discuss the effects of higher-curvature couplings and of an explicit cosmological term ($\Lambda$) on stability of such continuity and of massive excitations.Comment: 23 pages, Latex, the version to appear in Class. Quant. Gra

Determination of the time-dependent reaction coefficient and the heat flux in a nonlinear inverse heat conduction problem

Diffusion processes with reaction generated by a nonlinear source are commonly encountered in practical applications related to ignition, pyrolysis and polymerization. In such processes, determining the intensity of reaction in time is of crucial importance for control and monitoring purposes. Therefore, this paper is devoted to such an identification problem of determining the time-dependent coefficient of a nonlinear heat source together with the unknown heat flux at an inaccessible boundary of a one-dimensional slab from temperature measurements at two sensor locations in the context of nonlinear transient heat conduction. Local existence and uniqueness results for the inverse coefficient problem are proved when the first three derivatives of the nonlinear source term are Lipschitz continuous functions. Furthermore, the conjugate gradient method (CGM) for separately reconstructing the reaction coefficient and the heat flux is developed. The ill-posedness is overcome by using the discrepancy principle to stop the iteration procedure of CGM when the input data is contaminated with noise. Numerical results show that the inverse solutions are accurate and stable

Mass and angular momentum of asymptotically AdS or flat solutions in the topologically massive gravity

We study the conserved charges of supersymmetric solutions in the topologically massive gravity theory for both asymptotically flat and constant curvature geometries.Comment: REVTEX4, 8 pages, no figures, added 2 references and a few clarifying remark