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Search Results: 1 - 10 of 435711 matches for " J. - G. Demers "
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Hermiticity and the Cohomology Condition in Topological Yang-Mills Theory
J. -G. Demers
Physics , 1993, DOI: 10.1006/aphy.1994.1069
Abstract: The symmetries of the topological Yang-Mills theory are studied in the Hamiltonian formalism and the generators of the twisted N=2 superPoincar\'e algebra are explicitly constructed. Noting that the twisted Lorentz generators do not generate the Lorentz symmetry of the theory, we relate the two by extracting from the latter the twisted version of the internal SU(2) generator. The hermiticity properties of the various generators are also considered throughout, and the boost generators are found to be non-hermitian. We then recover the BRST cohomology condition on physical states from representation theory arguments.
Decoherence of the Unruh Detector
J. - G. Demers
Physics , 1995,
Abstract: As it is well known, the Minkowski vacuum appears thermally populated to a quantum mechanical detector on a uniformly accelerating course. We investigate how this thermal radiation may contribute to the classical nature of the detector's trajectory through the criteria of decoherence. An uncertainty-type relation is obtained for the detector involving the fluctuation in temperature, the time of flight and the coupling to the bath.
Fluctuations of the Unruh Temperature
J. -G. Demers
Physics , 1994, DOI: 10.1142/S0217732395001861
Abstract: Using the influence functional formalism, the problem of an accelerating detector in the presence of a scalar field in its ground state is considered in Minkowski space. As is known since the work of Unruh, to a quantum mechanical detector following a definite, classical acceleration, the field appears to be thermally excited. We relax the requirement of perfect classicality for the trajectory and substitute it with one of {\it derived} classicality through the criteria of decoherence. The ensuing fluctuations in temperature are then related with the time and the amplitude of excitation in the detector's internal degree of freedom.
Decoherence of Black Holes by Hawking Radiation
J. -G. Demers,C. Kiefer
Physics , 1995, DOI: 10.1103/PhysRevD.53.7050
Abstract: We discuss in detail the semiclassical approximation for the CGHS model of two-dimensional dilatonic black holes. This is achieved by a formal expansion of the full Wheeler-DeWitt equation and the momentum constraint in powers of the gravitational constant. In highest order, the classical CGHS solution is recovered. The next order yields a functional Schr\"odinger equation for quantum fields propagating on this background. We show explicitly how the Hawking radiation is recovered from this equation. Although described by a pure quantum state, the expectation value of the number operator exhibits a Planckian distribution with respect to the Hawking temperature. We then show how this Hawking radiation can lead to the decoherence of black hole superpositions. The cases of a superposition of a black hole with a white hole, as well as of a black hole with no hole, are treated explicitly.
Twisting to Abelian BF/Chern-Simons Theories
R. Brooks,J. -G. Demers,C. Lucchesi
Physics , 1993, DOI: 10.1016/0550-3213(94)90115-5
Abstract: Starting from a $D=3$, $N=4$ supersymmetric theory for matter fields, a twist with a Grassmann parity change is defined which maps the theory into a gauge fixed, abelian $BF$ theory on curved 3-manifolds. After adding surface terms to this theory, the twist is seen to map the resulting supersymmetric action to two uncoupled copies of the gauge fixed Chern-Simons action. In addition, we give a map which takes the $BF$ and Chern-Simons theories into Donaldson-Witten TQFT's. A similar construction, but with $N=2$ supersymmetry, is given in two dimensions.
Black Hole Entropy without Brick Walls
J. - G. Demers,R. Lafrance,R. C. Myers
Physics , 1995, DOI: 10.1103/PhysRevD.52.2245
Abstract: We present evidence which confirms a suggestion by Susskind and Uglum regarding black hole entropy. Using a Pauli-Villars regulator, we find that 't Hooft's approach to evaluating black hole entropy through a statistical-mechanical counting of states for a scalar field propagating outside the event horizon yields precisely the one-loop renormalization of the standard Bekenstein-Hawking formula, $S=\A/(4G)$. Our calculation also yields a constant contribution to the black hole entropy, a contribution associated with the one-loop renormalization of higher curvature terms in the gravitational action.
Role of the International Council for Laboratory Animal Science (ICLAS) in the promotion of care and use of laboratory animals in Southeast Europe
Kostomitsopoulos N.,Carbone Cecilia,Demers G.
Archives of Biological Sciences , 2008, DOI: 10.2298/abs0802175k
Abstract: The use of animals in research, teaching, and testing is regulated around the world by specific laws. Since regulatory processes are highly variable, a broad variability in the care and use of animals in scientific procedures exists internationally, as well as in the region of Southeast Europe. It is necessary to initiate an effort to promote the harmonization and improvement of laboratory animal science world-wide. The aim of this article is to explain the structure, organization, and aims of the International Council for Laboratory Animal Science (ICLAS) and to describe the role of this organization in the promotion of care and use of laboratory animals in this region of Europe.
The complexity of prognosis communication in heart failure: Patient and cardiologists’ preferences in the outpatient clinical setting  [PDF]
Patricia H. Strachan, Heather M. Arthur, Catherine Demers, Robert J. Robson
World Journal of Cardiovascular Diseases (WJCD) , 2013, DOI: 10.4236/wjcd.2013.31A017
Abstract:

Background: The determination of prognosis in heart failure (HF) has focused primarily on the identification of potential biological and physiological markers and not on communication. High morbidity and mortality rates suggest that patients require prognostic information to assist in life planning. This study examined the preferences of both patients with HF and cardiologists for prognosis communication in the outpatient clinical setting, with the aim of guiding practitioners in undertaking prognosis conversations. Methods: Using qualitative descriptive techniques informed by a grounded theory approach, 32 patients with HF and 9 cardiologists from outpatient settings in Ontario, Canada were interviewed to identify convergent preferences for prognosis communication. Strategies to enhance methodological rigor were employed. Results: Individualized, context-specific prognosis communication between patients and cardiologists was preferred. Two main themes and ten related attributes were identified to describe convergent preferences; 1) Set the Stage for Prognosis Communication, and 2) Map the HF route. Attributes reflected the complex, dynamic, interactive and iterative nature of prognosis communication preferences. Conclusions: Prognosis communication occurs within a complex, adaptive healthcare system. While specific preferences exist, changing contextual elements within and outside of the system create conditions that require cardiologists to adjust their approach to individual patients. Patients with HF and cardiologists each have preferences that affect their willingness and ability to engage in dyadic HF-specific prognosis communication. Findings have relevance for the implementation of any efforts, including HF guidelines, aimed at improving prognosis communication. Our findings, informed by a complexity science approach, offer an innovative and robust alternative to traditional linear approaches to prognosis communication.

Magellanic Cloud Periphery Carbon Stars IV: The SMC
William Kunkel,Serge Demers,M. J. Irwin
Physics , 2000, DOI: 10.1086/301401
Abstract: The kinematics of 150 carbon stars observed at moderate dispersion on the periphery of the Small Magellanic Cloud are compared with the motions of neutral hydrogen and early type stars in the Inter-Cloud region. The distribution of radial velocities implies a configuration of these stars as a sheet inclined at 73+/-4 degrees to the plane of the sky. The near side, to the South, is dominated by a stellar component; to the North, the far side contains fewer carbon stars, and is dominated by the neutral gas. The upper velocity envelope of the stars is closely the same as that of the gas. This configuration is shown to be consistent with the known extension of the SMC along the line of sight, and is attributed to a tidally induced disruption of the SMC that originated in a close encounter with the LMC some 0.3 to 0.4 Gyr ago. The dearth of gas on the near side of the sheet is attributed to ablation processes akin to those inferred by Weiner & Williams (1996) to collisional excitation of the leading edges of Magellanic Stream clouds. Comparison with pre LMC/SMC encounter kinematic data of Hardy, Suntzeff, & Azzopardi (1989) of carbon stars, with data of stars formed after the encounter, of Maurice et al. (1989), and Mathewson et al. (a986, 1988) leaves little doubt that forces other than gravity play a role in the dynamics of the H I.
ICP原子荧光光谱法分析贵金属
J.,W.,Skrabak,D.,R.,Demers,黄本立
分析化学 , 1987,
Abstract: 长期以来铅火试金法是分析贵金属的主要方法。但是该法很费时间,而且操作人员要有高度熟练的处理样品和解释所得结果的技巧。因而现代光谱仪器正在愈来愈多地被用于快速准确的分析。
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