Strongly Coupled Chameleon Fields: New Horizons in Scalar Field Theory

We show that as a result of non-linear self-interactions, scalar field theories that couple to matter much more strongly than gravity are not only viable but could well be detected by a number of future experiments, provided these are properly designed to do so.Comment: 4 pages, 3 figs. Typos corrected. Comments added. Phys. Rev. Lett. in prin

WMAPing the Universe: Supersymmetry, Dark Matter, Dark Energy, Proton Decay and Collider Physics

In this review we discuss constraints on minimal supersymmetric models of particle physics implied by the recent astrophysical observations of WMAP. Although the prospects of detecting supersymmetry increase and 90 percent of the available MSSM parameter space can safely be reached by the sensitivity of future colliders, nevertheless we pay particular emphasis on discussing regions of the appropriate phase diagrams, which -if realized - would imply that detection of supersymmetry, at least in the context of minimal models, could be out of colliders reach. We also discuss the importance of a precise determination of the radiative corrections to the muon anomalous magnetic moment, both theoretically and experimentally. Finally, we briefly commend upon recent evidence, supported by observations, on a dark energy component of the Universe, of as yet unknown origin, covering 73 percent of its energy content.Comment: Review paper, 69 pages Latex, 35 eps figures incorporate

Variations on the Vev Flip-Flop: Instantaneous Freeze-out and Decaying Dark Matter

In this work we consider a simple model for dark matter and identify regions of parameter space where the relic abundance is set via kinematic thresholds, which open and close due to thermal effects. We discuss instantaneous freeze-out, where dark matter suddenly freezes-out when the channel connecting dark matter to the thermal bath closes, and decaying dark matter, where dark matter freezes-out while relativistic and later decays when a kinematic threshold temporarily opens. These mechanisms can occur in the vicinity of a one-step or a two-step phase transition. In all cases thermal effects provide this dynamic behaviour, while ensuring that dark matter remains stable until the present day.Comment: 23 pages, 13 figures; v2: version matched to journal (JHEP), added a detailed discussion of further two-to-two processe

Imprint of a scalar era on the primordial spectrum of gravitational waves

Upcoming searches for the stochastic background of inflationary gravitational waves (GWs) offer the exciting possibility to probe the evolution of our Universe prior to Big Bang nucleosynthesis. In this spirit, we explore the sensitivity of future GW observations to a broad class of beyond-the-Standard-Model scenarios that lead to a nonstandard expansion history. We consider a new scalar field whose coherent oscillations dominate the energy density of the Universe at very early times, resulting in a scalar era prior to the standard radiation-dominated era. The imprint of this scalar era on the primordial GW spectrum provides a means to probe well-motivated yet elusive models of particle physics. Our work highlights the complementarity of future GW observatories across the entire range of accessible frequencies.Comment: 8 pages, 3 figures. v2: typos removed, updated references. v3: matches version published in Phys. Rev. Researc

Probing the gauge symmetry breaking of the early universe in 3-3-1 models and beyond by gravitational waves

Taking the 3-3-1 models (with $SU(3)_c \otimes SU(3)_L \otimes U(1)_Y$ gauge group) as examples, we study that a class of new physics models with extended gauge group could undergo one or several first-order phase transitions associated with the spontaneously symmetry breaking processes during the evolution of the universe, which can produce detectable phase transition gravitational wave (GW) signals at future GW experiments, such as LISA, BBO, DECIGO, SKA and aLIGO. These GW signals can provide new sources of GWs with different peak frequencies, and can be used to probe the evolution history of the universe.Comment: Published version for Physics Letters