12,586 research outputs found
Stabilizing Moduli with String Cosmology
In this talk I will discuss the role of finite temperature quantum
corrections in string cosmology and show that they can lead to a stabilization
mechanism for the volume moduli. I will show that from the higher dimensional
perspective this results from the effect of states of enhanced symmetry on the
one-loop free energy. These states lead not only to stabilization, but also
suggest an alternative model for cold dark matter. At late times, when the low
energy effective field theory gives the appropriate description of the
dynamics, the moduli will begin to slow-roll and stabilization will generically
fail. However, stabilization can be recovered by considering cosmological
particle production near the points of enhanced symmetry leading to the process
known as moduli trapping.Comment: Talk presented at PASCOS 2004. To be published in proceedings (World
Scientific, 2004
Reevaluating the Cosmological Origin of Dark Matter
The origin of dark matter as a thermal relic offers a compelling way in which
the early universe was initially populated by dark matter. Alternative
explanations typically appear exotic compared to the simplicity of thermal
production. However, recent observations and progress from theory suggest that
it may be necessary to be more critical. This is important because ongoing
searches probing the microscopic properties of dark matter typically rely on
the assumption of dark matter as a single, unique, thermal relic. On general
grounds I will argue that non-thermal production of dark matter seems to be a
robust prediction of physics beyond the standard model. However, if such models
are to lead to realistic phenomenology, they must sit in a restrictive
theoretical framework. As we will show, as a consequence of such restrictions,
viable models will result in concrete and testable predictions. Although many
challenges remain, the non-thermal component of such models may offer a new way
to test string theories that are formulated to provide realistic particle
physics near the electroweak scale.Comment: 22 pages, no figure
Children and international relations : a new site of knowledge?
Recent years have seen the growth of approaches critical of traditional state-centred examinations of international relations, arguing instead for analyses that recognise actors and methods previously held largely silent within the mainstream International Relations (IR) discourse. This article argues that children are a group of actors worthy of similar recognition. Despite the fact that 'childhood studies' are comparatively well established in a number of academic disciplines, similar recognition has been later in coming to the study of IR. This article aims to address this perceived gap in the literature by first of all outlining the ways in which the discourse surrounding the child in IR has so far developed. This leads into an, examination of how the child may potentially best be conceptualised within the mainstream discourse and the implications of the inclusion of children as a 'site of knowledge' through which the international system may be more clearly understood.Publisher PDFPeer reviewe
Is More Better? The Impact of Postsecondary Education on the Economic and Social Well-Being of American Society
Provides a review of research literature that examines the impact of higher education on individuals and society. Looks at economic and non-economic benefits and costs associated with an increase in public investment in postsecondary education
Dilaton Dynamics from Production of Tensionless Membranes
In this paper we consider classical and quantum corrections to cosmological
solutions of 11D SUGRA coming from dynamics of membrane states. We first
consider the supermembrane spectrum following the approach of Russo and
Tseytlin for consistent quantization. We calculate the production rate of BPS
membrane bound states in a cosmological background and find that such effects
are generically suppressed by the Planck scale, as expected. However, for a
modified brane spectrum possessing enhanced symmetry, production can be finite
and significant. We stress that this effect could not be anticipated given only
a knowledge of the low-energy effective theory. Once on-shell, inclusion of
these states leads to an attractive force pulling the dilaton towards a fixed
point of S-duality, namely . Although the SUGRA description breaks down
in this regime, inclusion of the enhanced states suggests that the center of
M-theory moduli space is a dynamical attractor. Morever, our results seem to
suggest that string dynamics does indeed favor a vacuum near fixed points of
duality.Comment: 39 pages, 7 figures, minor corrections and reference adde
- …