Cosmological reheating describes the transition of the post-inflationary universe to a hot and thermal state. In order to shed light on the underlying dynamics of this process, we propose to ...quantum-simulate the reheating-like dynamics of a generic cosmological single-field model in an ultracold Bose gas. In our setup, the excitations on top of an atomic Bose-Einstein condensate play the role of the particles produced by the decaying inflaton field after inflation. Expanding spacetime as well as the background oscillating inflaton field are mimicked in the non-relativistic limit by a time dependence of the atomic interactions, which can be tuned experimentally via Feshbach resonances. As we illustrate by means of classical-statistical simulations for the case of two spatial dimensions, the dynamics of the atomic system exhibits the characteristic stages of far-from-equilibrium reheating, including the amplification of fluctuations via parametric instabilities and the subsequent turbulent transport of energy towards higher momenta. The transport is governed by a non-thermal fixed point showing universal self-similar time evolution as well as a transient regime of prescaling with time-dependent scaling exponents. While the classical-statistical simulations can capture only the earlier stages of the dynamics for weak couplings, the proposed experiment has the potential of exploring the evolution up to late times even beyond the weak coupling regime.
A search for the standard model Higgs boson (H) decaying to b b-bar when produced in association with a weak vector boson (V) is reported for the following channels: W(mu nu)H, W(e nu)H, W(tau nu)H, ...Z(mu mu)H, Z(e e)H, and Z(nu nu)H. The search is performed in data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at sqrt(s) = 7 TeV and up to 18.9 inverse femtobarns at sqrt(s) = 8 TeV, recorded by the CMS experiment at the LHC. An excess of events is observed above the expected background with a local significance of 2.1 standard deviations for a Higgs boson mass of 125 GeV, consistent with the expectation from the production of the standard model Higgs boson. The signal strength corresponding to this excess, relative to that of the standard model Higgs boson, is 1.0 +/- 0.5.
We study the impact of attractive self-interactions on the nonequilibrium dynamics of relativistic quantum fields with large occupancies at low momenta. Our primary focus is on Bose-Einstein ...condensation and nonthermal fixed points in such systems. As a model system we consider O(N)-symmetric scalar field theories. We use classical-statistical real-time simulations, as well as a systematic 1/N expansion of the quantum (2PI) effective action to next-to-leading order. When the mean self-interactions are repulsive, condensation occurs as a consequence of a universal inverse particle cascade to the zero-momentum mode with self-similar scaling behavior. For attractive mean self-interactions the inverse cascade is absent and the particle annihilation rate is enhanced compared to the repulsive case, which counteracts the formation of coherent field configurations. For N >= 2, the presence of a nonvanishing conserved charge can suppress number changing processes and lead to the formation of stable localized charge clumps, i.e. Q-balls.
This dissertation examines how the stalled process of democratization in post-communist hybrid regimes has affected their environmental policymaking processes and protection outcomes. I examine how ...shallow democratization in the rule of law, administrative state agencies, and civil society in the Republic of Armenia has influenced environmental policymaking and protection over four time periods: the Soviet period (1980s–1991); early democratic transition period (1992–1994); mid-transition period (1995–1998); and late transition period (1998–2003). Two critical national environmental issues are analyzed in detail: protection of Lake Sevan and forestry resources. I employ two complementary research methodologies to study the change in environmental protection over the transition period: (1) in-depth interviews with over sixty experts and officials in Armenia during the period from 1997–2001; and (2) content analysis of official documents and environmental news coverage. My research demonstrates that, contrary to hopeful expectations, Lake Sevan and forestry resources have both been seriously degraded during the transition period (despite different starting points at the end of Soviet rule) due to the incomplete development of democratic institutions and governance. I therefore conclude that democratic stagnation adversely affects environmental protection in post-communist hybrid regimes. Furthermore, environmental protection in shallow hybrid democracies is fundamentally different than in either consolidated democracies or authoritarian regimes. There is a unique pattern to this eco-political dynamic, as we see a decline in the benefits of the strong state to make enlightened environmental decisions, and an incomplete gain in democracy's advantages of increased pluralism, openness, and information sharing. Environmental protection in hybrid regimes such as Armenia is characterized by the weakening of administrative agencies in charge of environmental protection, decline of pre-independence environmental movements, lack of formal mechanisms to allow NGOs to participate in environmental policymaking, passage of ineffectual environmental laws that are difficult to implement and monitor, failure of attempts to use legal mechanisms, short bursts of activity and short-term increases in capacity through international funding that unfortunately are not maintained, and increasing dependence on international aid. Nevertheless, there may be hope for improvement in the future due to increasing pluralism and decentralization of environmental policymaking and increasing interaction with international organizations.
PDF
