Constraining SUSY GUTs and Inflation with Cosmology

In the framework of Supersymmetric Grand Unified Theories (SUSY GUTs), the universe undergoes a cascade of symmetry breakings, during which topological defects can be formed. We address the question of the probability of cosmic string formation after a phase of hybrid inflation within a large number of models of SUSY GUTs in agreement with particle and cosmological data. We show that cosmic strings are extremely generic and should be used to relate cosmology and high energy physics. This conclusion is employed together with the WMAP CMB data to strongly constrain SUSY hybrid inflation models. F-term and D-term inflation are studied in the SUSY and minimal SUGRA framework. They are both found to agree with data but suffer from fine tuning of their superpotential coupling (\lambda \lesssim 3\times 10^(-5) or less). Mass scales of inflation are also constrained to be less than M \lesssim 3\times 10^(15) GeV.Comment: Based on talks given by J. Rocher at the "IAP Colloquium", Paris in july 2004, at "COSMO 04", Toronto in September 2004, at the Workshop "Quest For Unification", CERN in December 2004 and at the "Einstein's Century Meeting", Paris in june 2005. To appear in the Proceedings of the "Einstein's Century Meeting", Ed. J.-M. Alimi, A. Furzfa, AIP, Paris (2006

DD-term inflation, cosmic strings, and consistency with cosmic microwave background measurement

Standard D-term inflation is studied in the framework of supergravity. D-term inflation produces cosmic strings, however it can still be compatible with CMB measurements without invoking any new physics. The cosmic strings contribution to the CMB data is not constant, nor dominant, contrary to some previous results. Using current CMB measurements, the free parameters (gauge and superpotential couplings, as well as the Fayet-Iliopoulos term) of D-term inflation are constrained.Comment: 1 Latex file and 3 figures. accepted for publication in Physical Review Letter

Scientific cooperation in the South China Sea: another lever for China?

Overview Security issues in the South China Sea are often studied, whereas analysis of scientific cooperation in those waters is rare, thinly spread and short. This paper looks at shared priorities, China\u27s leading role in launching scientific programs, implications for the environment, and the use of scientific cooperation as a power vector. The research space is increasingly well controlled, but that control isn’t the product of scientific cooperation. It’s the result of China leading research programs. Scientific cooperation hasn’t reduced mistrust, and common interests don’t prevail. In relations between Southeast Asia and China, the fulcrum is asymmetry. The differences in scientific cooperation noted in this paper demonstrate that asymmetry and its serious long-term consequences for neighbouring countries

Avoiding the blue spectrum and the fine-tuning of initial conditions in hybrid inflation

Hybrid inflation faces two well-known problems: the blue spectrum of the non-supersymmetric version of the model and the fine-tuning of the initial conditions of the fields leading to sufficient inflation to account for the standard cosmological problems. They are investigated by studying the exact two-fields dynamics instead of assuming slow-roll. When the field values are restricted to be less than the reduced Planck mass, a non-negligible part of the initial condition space (around 15% depending on potential parameters) leads to successful inflation. Most of it is located outside the usual inflationary valley and organized in continuous patterns instead of being isolated as previously found. Their existence is explained and their properties are studied. This shows that no excessive fine-tuning is required for successful hybrid inflation. Moreover, by extending the initial condition space to planckian-like or super-planckian values, inflation becomes generically sufficiently long and can produce a red-tilted scalar power spectrum due to slow-roll violations. The robustness of these properties is confirmed by conducting our analysis on three other models of hybrid-type inflation in various framework: "smooth" and "shifted" inflation in SUSY and SUGRA, and "radion assisted" gauge inflation. A high percentage of successful inflation for smooth hybrid inflation (up to 80%) is observed.Comment: 20 pages, 14 figures. Some refs added/updated. New results for Smooth and Shifted hybrid models. To appear in PR

Genericity of Cosmic Strings Formation in SUSY GUTs

The idea of GUT implies that the universe went through a series of phase transitions during which topological defects are expected to form. We investigate here the genericity of cosmic strings formation in realistic SUSY GUTs models. We conclude that all acceptable symmetry breaking schemes produce cosmic strings after the last inflationary phase. Generically, as they form at the end of inflation, they have a mass of order of the GUT scale. Since cosmological data coming from CMB measurements do not show evidence for such strings, they constrain GUT scale physics.Comment: 4 pages, talk at the XXXIX Rencontres de Moriond (La Thuile, March 2004), to appear in the proceeding

Fractal initial conditions and natural parameter values in hybrid inflation

We show that the initial field values required to produce inflation in the two fields original hybrid model, and its supergravity F-term extension, do not suffer from any fine-tuning problem, even when the fields are restricted to be sub-planckian and for almost all potential parameter values. This is due to the existence of an initial slow-roll violating evolution which has been overlooked so far. Due to the attractor nature of the inflationary valley, these trajectories end up producing enough accelerated expansion of the universe. By numerically solving the full non-linear dynamics, we show that the set of such successful initial field values is connected, of dimension two and possesses a fractal boundary of infinite length exploring the whole field space. We then perform a Monte-Carlo-Markov-Chain analysis of the whole parameter space consisting of the initial field values, field velocities and potential parameters. We give the marginalised posterior probability distributions for each of these quantities such that the universe inflates long enough to solve the usual cosmological problems. Inflation in the original hybrid model and its supergravity version appears to be generic and more probable by starting outside of the inflationary valley. Finally, the implication of our findings in the context of the eternal inflationary scenario are discussed.Comment: 16 pages, 16 figures, uses RevTeX. Lyapunov exponents and references added, matches published versio