5,767 research outputs found
Fermi-bounce cosmology and the fermion curvaton mechanism
A nonsingular bouncing cosmology can be achieved by introducing a fermion
field with BCS condensation occurring at high energy scales. In this paper we
are able to dilute the anisotropic stress near the bounce by means of releasing
the gap energy density near the phase transition between the radiation and
condensate states. In order to explain the nearly scale-invariant CMB spectrum,
another fermion field is required. We investigate one possible curvaton
mechanism by involving one another fermion field without condensation where the
mass is lighter than the background field. We show that, by virtue of the
fermion curvaton mechanism, our model can satisfy the latest cosmological
observations very well, and that the fermion species involved may realize a
cosmological see-saw mechanism after one finely tunes model parameters.Comment: 9 pages, 4 figure
Singlets in Composite Higgs Models in light of the LHC di-photon searches
Models of compositeness can successfully address the origin of the Higgs
boson, as a pseudo Nambu Goldstone boson (pNGB) of a spontaneously broken
global symmetry, and flavour physics via the partial compositeness mechanism.
If the dynamics is generated by a confining gauge group with fermionic matter
content, there exists only a finite set of models that have the correct
properties to account for the Higgs and top partners at the same time. In this
letter we explore the theory space of this class of models: remarkably, all of
them contain - beyond the pNGB Higgs - a pNGB singlet, , which couples to
Standard Model gauge bosons via Wess-Zumino-Witten interactions, thus providing
naturally a resonance in di-boson at the LHC. With the assumption that the
recently reported di-photon excess at 750 GeV at the LHC arises from the
a-resonance, we propose a generic approach on how to delineate the best
candidate for composite Higgs models with top-partners. We find that
constraints from other di-boson searches severely reduce the theory space of
the models under consideration. For the models which can explain the di-photon
excess, we make precise and testable predictions for the width and other
di-boson resonance searches.Comment: 5 pages, 2 Tables; v2: clarifying comments added, typos fixed,
references update
Chiral selection and frequency response of spiral waves in reaction-diffusion systems under a chiral electric field
Chirality is one of the most fundamental properties of many physical,
chemical and biological systems. However, the mechanisms underlying the onset
and control of chiral symmetry are largely understudied. We investigate
possibility of chirality control in a chemical excitable system (the BZ
reaction) by application of a chiral (rotating) electric field using the
Oregonator model. We find that unlike previous findings, we can achieve the
chirality control not only in the field rotation direction, but also opposite
to it, depending on the field rotation frequency. To unravel the mechanism, we
further develop a comprehensive theory of frequency synchronization based on
the response function approach. We find that this problem can be described by
the Adler equation and show phase-locking phenomena, known as the Arnold
tongue. Our theoretical predictions are in good quantitative agreement with the
numerical simulations and provide a solid basis for chirality control in
excitable media.Comment: 21 pages with 9 figures; update references; to appear in J. Chem.
Phy
- …