14,393 research outputs found
Time Evolution of Temperature and Entropy of Various Collapsing Domain Walls
We investigate the time evolution of the temperature and entropy of
gravitationally collapsing domain walls as seen by an asymptotic observer. In
particular, we seek to understand how topology and the addition of a
cosmological constant affect the gravitational collapse. Previous work has
shown that the entropy of a spherically symmetric collapsing domain approaches
a constant. In this paper, we reproduce these results, using both a fully
quantum and a semi-classical approach, then we repeat the process for a de
Sitter Schwarzschild domain wall (spherical with cosmological constant) and a
(3+1) BTZ domain wall (cylindrical). We do this by coupling a scalar field to
the background of the domain wall and analyzing the spectrum of radiation as a
function of time. We find that the spectrum is quasi-thermal, with the degree
of thermality increasing as the domain wall approaches the horizon. The thermal
distribution allows for the determination of the temperature as a function of
time, and we find that the late time temperature is very close to the Hawking
temperature and that it also exhibits the proper scaling with the mass. From
the temperature we find the entropy. Since the collapsing domain wall is what
forms a black hole, we can compare the results to those of the standard
entropy-area relation. We find that the entropy does in fact approach a
constant that is close to the Hawking entropy. However, both the de Sitter
Schwarzschild domain wall and the (3+1) BTZ domain wall show periods of
decreasing entropy, which suggests that spontaneous collapse may be prevented.Comment: This paper is a merging of two previously submitted papers: Time
Evolution of Temperature and Entropy of a Gravitationally Collapsing Cylinder
[arXiv:1106.2278]; Time Evolution of Temperature and Entropy of a
Gravitationally Collapsing de Sitter Schwarzschild Domain Wal
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The impact of market and supply configurations on the costs of tendering in the construction industry
The cost of tendering in the construction industry is widely suspected to be excessive, but there is little robust empirical evidence to demonstrate this. It also seems that innovative working practices may reduce the costs of undertaking construction projects and the consequent improvement in relationships should increase overall value for money. The aim of this proposed research project is to develop mechanisms for measuring the true costs of tendering based upon extensive in-house data collection undertaken in a range of different construction firms. The output from this research will enable all participants in the construction process to make better decisions about how to select members of the team and identify the price and scope of their obligations
Alien Registration- Greenwood, Charles H. (Bethel, Oxford County)
https://digitalmaine.com/alien_docs/15692/thumbnail.jp
Capacity strengthening in malaria research: the Gates Malaria Partnership.
The Gates Malaria Partnership (GMP) includes five African and four European partner institutions. Its research programme has five priority areas involving an extensive range of field-based studies. GMP research has contributed significantly to the development of new research consortia investigating strategies for improving means of malaria control, and has already had an impact on policy and practice. A substantial investment in innovative training activities in malaria has enhanced knowledge and practice of malaria control at all levels from policy making to local community involvement. Capacity development, notably through a PhD programme, has been an underlying feature of all aspects of the programme
Time Evolution of Entropy in Gravitational Collapse
We study the time evolution of the entropy of a collapsing spherical domain
wall, from the point of view of an asymptotic observer, by investigating the
entropy of the entire system (i.e. domain wall and radiation) and induced
radiation alone during the collapse. By taking the difference, we find the
entropy of the collapsing domain wall, since this is the object which will form
a black hole. We find that for large values of time (times larger than
), the entropy of the collapsing domain wall is a constant,
which is of the same order as the Bekenstein-Hawking entropy.Comment: 9 pages, 6 figure
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