12 research outputs found
Cosmology from Moduli Dynamics
We investigate moduli field dynamics in supergravity/M-theory like set ups
where we turn on fluxes along some or all of the extra dimensions. As has been
argued in the context of string theory, we observe that the fluxes tend to
stabilize the squashing (or shape) modes. Generically we find that at late
times the shape is frozen while the radion evolves as a quintessence field. At
earlier times we have a phase of radiation domination where both the volume and
the shape moduli are slowly evolving. However, depending on the initial
conditions and the parameters of the theory, like the value of the fluxes,
curvature of the internal manifold and so on, the dynamics of the internal
manifold can be richer with interesting cosmological consequences, including
inflation.Comment: 38 pages, 6 figures; references adde
Hamiltonian formulation for the classical EM radiation-reaction problem: application to the kinetic theory for relativistic collisionless plasmas
A notorious difficulty in the covariant dynamics of classical charged
particles subject to non-local electromagnetic (EM) interactions arising in the
EM radiation-reaction (RR) phenomena is due to the definition of the related
non-local Lagrangian and Hamiltonian systems. The lack of a standard
Lagrangian/Hamiltonian formulation in the customary asymptotic approximation
for the RR equation may inhibit the construction of consistent kinetic and
fluid theories. In this paper the issue is investigated in the framework of
Special Relativity. It is shown that, for finite-size spherically-symmetric
classical charged particles, non-perturbative Lagrangian and Hamiltonian
formulations in standard form can be obtained, which describe particle dynamics
in the presence of the exact EM RR self-force. As a remarkable consequence,
based on axiomatic formulation of classical statistical mechanics, the
covariant kinetic theory for systems of charged particles subject to the EM RR
self-force is formulated in Hamiltonian form. A fundamental feature is that the
non-local effects enter the kinetic equation only through the retarded particle
4-position, which permits the construction of the related non-local fluid
equations. In particular, the moment equations obtained in this way do not
contain higher-order moments, allowing as a consequence the adoption of
standard closure conditions. A remarkable aspect of the theory concerns the
short delay-time asymptotic expansions. Here it is shown that two possible
expansions are permitted. Both can be implemented for the single-particle
dynamics as well as for the corresponding kinetic and fluid treatments. In the
last case, they are performed a posteriori on the relevant moment equations
obtained after integration of the kinetic equation over the velocity space.
Comparisons with literature are pointed out
Cosmological evolution and statefinder diagnostic for new holographic dark energy model in non flat universe
In this paper, the holographic dark energy model with new infrared cut-off
proposed by Granda and Oliveros has been investigated in spatially non flat
universe. The dependency of the evolution of equation of state, deceleration
parameter and cosmological evolution of Hubble parameter on the parameters of
new HDE model are calculated. Also, the statefinder parameters and in
this model are derived and the evolutionary trajectories in plane are
plotted. We show that the evolutionary trajectories are dependent on the model
parameters of new HDE model. Eventually, in the light of SNe+BAO+OHD+CMB
observational data, we plot the evolutionary trajectories in and
planes for best fit values of the parameters of new HDE model.Comment: 11 pages, 5 figures, Accepted by Astrophys. Space Sc
Early Lessons Learned in the ENDORSE Project: Legal Challenges and Possibilities in Developing Data Protection Compliance Software
Part 3: PoliciesInternational audienceSoftware can help businesses comply with data protection regulation. The development of such compliance software may be desirable because data protection compliance is difficult or burdensome to achieve, and especially for small and medium enterprises. Building software capable of providing proper legal guidance, or even enforcing the law, is, however, non-evident. This paper addresses some of the complexities and opportunities involved in the development of such software from a legal perspective. The paper focuses on the identification of relevant regulation, legal norm conflicts and the implementation of open norms in software