78 research outputs found
Brane Cosmology with Non-Static Bulk
We study the brane world motion in non-static bulk by generalizing the second
Randall-Sundrum scenario Explicitly, we take the bulk to be a Vaidya-AdS
metric, which describes the gravitational collapse of a spherically symmetric
null dust fluid in Anti-de Sitter spacetime. We point out that during an
inflationary phase on the brane, black holes will tend to be thermally
nucleated in the bulk We analyze the thermodynamical properties of this
brane-world.We point out that during an inflationary phase on the brane, black
holes will tend to be thermally nucleated in the bulk. Thermal equilibrium of
the system is discussed. We calculate the late time behavior of this system,
including 1-loop effects. We argue that at late times a sufficiently large
black hole will relax to a point of thermal equilibrium with the brane-world
environment. This result has interesting implications for early-universe
cosmology.Comment: 3 pages, Talk given at DPF 2000: The meeting of the Division of
Particles and Fields of the American Physical Society, Ohio, 9 - 12
August200
Thermal Equilibration of Brane-Worlds
We analyze the thermodynamical properties of brane-worlds, with a focus on
the second model of Randall and Sundrum. We point out that during an
inflationary phase on the brane, black holes will tend to be thermally
nucleated in the bulk. This leads us to ask the question: Can the black hole -
brane-world system evolve towards a configuration of thermal equilibrium? To
answer this, we generalize the second Randall-Sundrum scenario to allow for
non-static bulk regions on each side of the brane-world. Explicitly, we take
the bulk to be a {\it Vaidya-AdS} metric, which describes the gravitational
collapse of a spherically symmetric null dust fluid in Anti-de Sitter
spacetime. Using the background subtraction technique to calculate the
Euclidean action, we argue that at late times a sufficiently large black hole
will relax to a point of thermal equilibrium with the brane-world environment.
These results have interesting implications for early-universe cosmology.Comment: 4 pages REVTeX. The basic argument is simplified. Version to appear
in Physics Letters
Closed String Thermodynamics and a Blue Tensor Spectrum
The BICEP-2 team has recently reported the positive detection of cosmic microwave background Bmode polarization. Although uncertainties due to galactic dust foregrounds remain, it is a constructive exercise to work out the implications of presuming some part of the detected B-mode signal to be due to primordial gravitational waves. Were a positive detection of a tensor-to-scalar ratio larger than r greater than or similar to O(10(-2)) confirmed, detecting a tilt in the tensor spectrum comparable to that observed for the scalar power spectrum becomes in principle possible. We wish to explore in this brief paper the possibility of there being a blue tilt to the primordial gravitational-wave spectrum. Such a tilt would be incompatible with standard inflationary models, although it was predicted some years ago in the context of a mechanism that thermally generates the primordial perturbations through a Hagedorn phase of string cosmology. By scrutinizing the data with priors informed by a model that is immediately falsifiable, but which predicts features that may be favored by the data-namely a blue tensor tilt with an induced and complementary red tilt to the scalar spectrum, with a naturally large tensor-to-scalar ratio that relates to both-we offer a useful straw model against which to test the predictions of single-field inflation
Proposing a model for the effect of performance-based budgeting on the qualities of higher education in Iraq
Nowadays, rivalry can be observed not just between businesses, but also between universities. Higher education institutions have been under increasing pressure from external factors including labor and education market rivalry to improve the quality of their programs by reevaluating their organizational structures and management practices. This study set out to determine how performance-based budgeting would affect the quality of Iraq's postsecondary institutions. The statistical subjects of this study are those involved in performance-based budgeting in Iraqi universities, including the deans of the faculty and deputy deans, the director of the accounting department, and the financial and accounting staff. Morgan's table suggests a minimum sample size of n=246. This is because 3519 individuals were sampled from the population of non-professional private higher education institutions in Iraq. A total of 198 completed surveys were submitted. The collected data from the questionnaire was analyzed using a structured equation model. The results indicated that performance-based budgeting benefited greatly from considering organizational commitment and rewards mechanisms. The results, however, showed that the competence of managers played no impact in the introduction of performance-based budgeting in Iraq's higher education sector. However, the results showed that performance-based budgeting had no effect on the quality of higher education in Iraq, and neither did the competency nor the organizational commitment of managers in these institutions, nor did reward schemes
From Conflict to Cooperation: A Multi-Methodological Approach to Managing the Solid Waste Crisis in Lebanon
The management of solid waste in Lebanon has evolved into a complex issue, marked by its deleterious environmental, economic, and public health ramifications for both civilians and the state exchequer. Despite the longstanding nature of Lebanon's municipal waste predicament, it escalated to catastrophic proportions in 2015 following the closure of Naameh, the nation's largest landfill. The persisting crisis from 2015 endures due to the government's inadequate and poorly conceived solutions, with the potential to rekindle at any juncture. This paper addresses two fundamental concerns. Initially, a comprehensive portrayal of the municipal solid waste scenario in Lebanon is provided, encompassing its diverse facets. Subsequently, the researchers advocate an integrative approach amalgamating centralized and decentralized systems. Pioneering a strategic proposal to address Lebanon's solid waste predicament, the researchers employ a Journey-Making (JM) methodology to discern direct and indirect actors. Subsequently, a game theory approach, facilitated by the Graph Model for Conflict Resolution (GMCR+) software, is utilized to derive solutions that cater to the satisfaction of all involved parties. The selection of the optimal scenario is contingent upon the available options for the primary stakeholders, factoring in the political, sectarian, economic, and environmental landscape of Lebanon
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