A Neutrino Mass Matrix Model with many Quantum charges and No SUSY

We present a model based on our favourite gauge group which we call Anti-GUT and which in its extended form to be applied for neutrinos in the see-saw picture consists in that we have for each family separately a set of gauge fields as in the Standard Model plus a gauged (B-L)-charge. It may function as a concrete model manifestation of the type of model suggested by some general statistical considerations as to what a mass matrix model is to be to match naturally the rough features of the spectrum and the baryon asymmetry so nicely obtained in see-saw models along the Fukugita-Yanagida scheme.Comment: 20 pages, Latex2e; Contribution to The Scandinavian Neutrino Workshop, Uppsala, Sweden, 8-10 February 200

Naturalness of Neutralino Dark Matter

We investigate the level of fine-tuning of neutralino Dark Matter below 200 GeV in the low-energy phenomenological minimal supersymmetric Standard Model taking into account the newest results from XENON100 and the Large Hadron Collider as well as all other experimental bounds from collider physics and the cosmological abundance. We find that current and future direct Dark Matter searches significantly rule out a large area of the untuned parameter space, but solutions survive which do not increase the level of fine-tuning. As expected, the level of tuning tends to increase for lower cross-sections, but regions of resonant neutralino annihilation still allow for a band at light masses, where the fine-tuning stays small even below the current experimental limits for direct detection cross-sections. For positive values of the supersymmetric Higgs mass parameter \mu large portions of the allowed parameter space are excluded, but there still exist untuned solutions at higher neutralino masses which will essentially be ruled out if XENON1t does not observe a signal.For negative \mu untuned solutions are not much constrained by current limits of direct searches and, if the neutralino mass was found outside the resonance regions, a negative \mu-term would be favored from a fine-tuning perspective. Light stau annihilation plays an important role to fulfill the relic density condition in certain neutralino mass regions. Finally we discuss, in addition to the amount of tuning for certain regions in the neutralino mass-direct detection cross-section plane, the parameter mapping distribution if the allowed model parameter space is chosen to be scanned homogeneously (randomized).Comment: v2: 29 pages, 16 figures. Published versio

LHC Tests of Light Neutralino Dark Matter without Light Sfermions

We address the question how light the lightest MSSM neutralino can be as dark matter candidate in a scenario where all supersymmetric scalar particles are heavy. The hypothesis that the neutralino accounts for the observed dark matter density sets strong requirements on the supersymmetric spectrum, thus providing an handle for collider tests. In particular for a lightest neutralino below 100 GeV the relic density constraint translates into an upper bound on the Higgsino mass parameter $\mu$ in case all supersymmetric scalar particles are heavy. One can define a simplified model that highlights only the necessary features of the spectrum and their observable consequences at the LHC. Reinterpreting recent searches at the LHC we derive limits on the mass of the lightest neutralino that, in many cases, prove to be more constraining than dark matter experiments themselves.Comment: 22 pages, 8 figure

Neutrino Oscillations in Extended Anti-GUT Model

What we call the Anti-GUT model is extended a bit to include also right-handed neutrinos and thus make use of the see-saw mechanism for neutrino masses. This model consists in assigning gauge quantum numbers to the known Weyl fermions and the three see-saw right-handed neutrinos. Each family (generation) is given its own Standard Model gauge fields and a gauge field coupled to the $B-L$ quantum number for that family alone. Further we assign a rather limited number of Higgs fields, so as to break these gauge groups down to the Standard Model gauge group and to fit, w.r.t. order of magnitude, the spectra and mixing angles of the quarks and leptons. We find a rather good fit, which for neutrino oscillations favours the small mixing angle MSW solution, although the mixing angle predicted is closest to the upper side of the uncertainty range for the measured solar neutrino mixing angle. An idea for making a ``finetuning''-principle to ``explain'' the large ratios found empirically in physics, and answer such questions as ``why is the weak scale low compared to the Planck scale?'', is proposed. A further very speculative extension is supposed to ``explain'' why we have three families.Comment: 40 page LaTeX file; talk given at the Second Tropical Workshop on Particle Physics and Cosmology, San Juan, Puerto Rico, May 200

Boundary-Induced Phase Transitions in Equilibrium and Non-Equilibrium Systems

Boundary conditions may change the phase diagram of non-equilibrium statistical systems like the one-dimensional asymmetric simple exclusion process with and without particle number conservation. Using the quantum Hamiltonian approach, the model is mapped onto an XXZ quantum chain and solved using the Bethe ansatz. This system is related to a two-dimensional vertex model in thermal equilibrium. The phase transition caused by a point-like boundary defect in the dynamics of the one-dimensional exclusion model is in the same universality class as a continous (bulk) phase transition of the two-dimensional vertex model caused by a line defect at its boundary. (hep-th/yymmnnn)Comment: Latex 10pp, Geneva preprint UGVA-DPT 1993/07-82