14th International Symposium on Particles, Strings and Cosmology (PASCOS '08)
According to Doering and Isham the spectral topos corresponds to any quantum system. The descriptions of the systems become similar to these given by classical theories. Topoi can also modify local smooth spacetime structure. Supposing that a quantum system modifies the local spacetime structure and interacts with a gravitational field via the spectral topos, a natural pattern for non-gravitating quantum zero-point modes of the system, appears. A way how to add gravity into the spectral topos of a system is presented.
Linear confinement in holographic QCD can be obtained with a soft-wall quadratic dilaton background. We present a dynamical five-dimensional model realizing this setup and discuss the implications for the hypothetical string theory dual to QCD.
Searches for neutrinoless double beta decays could determine if neutrinos are Majorana particles and could measure their absolute mass scale. The initial stage of the Enriched Xenon Observatory project, EXO-200, will look for two-neutrino and neutrinoless double-beta decays of Xe-136 in a liquid-xenon time-projection chamber. By combining the ionization signal with detection of the scintillation light collected in Large Area Avalanche Photodiodes (LAAPDs), an energy resolution of about 1.4% at the decay energy can be achieved.
A new test of the LCDM concordance cosmology is presented.
We systematically explore the parameter space of the state-of-the-art brane-antibrane inflation model (Baumann et al.) which is most rigorously derived from string theory, applying the COBE normalization and constraints on the spectral index. We define an effective volume in parameter space consistent with the constraints, and show that the fine tuning problem is this model is alleviated by four orders of magnitude for the optimal parameter values, relative to a fiducial point which has previously been considered.
The Pierre Auger Observatory in Malargue, Argentina, is the world\'s largest detector for the study of the origin of ultrahigh energy cosmic rays. The experiment stretches over 3000 km^2 and measures cosmic rays with energies above 10^18 eV using two complementary detector types: an array of 1600 particle detectors on the ground, and 4 fluorescence detectors overlooking the ground array from the periphery. The Observatory is now nearing completion, but scientific data taking started at the beginning of 2004.
Using the general structure of the vacuum polarization tensor at non-zero temperature T and finite magnetic field B, the ring contribution to QED effective potential is determined beyond the static (zero momentum) limit. In the limit of weak magnetic field and at high temperature, the improved ring potential consists of a term proportional to T4®5=2, in ad-dition to the well-known T4®3=2 term. In the limit of strong magnetic field, where QED dynamics is dominated by the lowest Landau level (LLL), the ring potential consists of a novel term proportional to 2¼eB m2 ln ¡2®¼ eB m2 ¢.
The validity of the perturbative analysis during inflation imposes bounds on the inflationary parameters. For single field inflation, the current experimental bounds on non-Gaussianity necessarily imply that the physics is weakly coupled at CMB scales. In this talk, I will show that for models with a scale dependent sound speed, the system can become strongly coupled at lower scale. I will also discuss multiple field models which can produce non-Gaussianity at CMB scales. In these scenarios, the extra scalar fields are strongly coupled in a large part of the parameter space.
We study the possibility of detecting departures from GR using the tomographic surveys as Pan-starrs and LSST (Will be updated).
In this talk we will focus on the supergravity duals of BPS states in N=4 Super Yang-Mills. In particular, we will describe how one can obtain a universal AdS bubbling picture for 1/4 and 1/8 BPS geometries, in analogy with the well-established 1/2 BPS droplet picture of LLM. In addition, we will show how interactions of two-matrix (1/4 BPS) states can be understood in terms of those of the much simpler single matrix (1/2 BPS) states.