Prospects for Finding Sterile Neutrino Dark Matter at KATRIN

We discuss under what circumstances a signal in upcoming laboratory searchesfor keV-scale sterile neutrinos would be compatible with those particles beinga sizable part or all of dark matter. In the parameter space that will beexperimentally accessible by KATRIN/TRISTAN, strong X-ray limits need to berelaxed and dark matter overproduction needs to be avoided. We discusspostponing the dark matter production to lower temperatures, a reduced sterileneutrino contribution to dark matter, and a reduction of the branching ratio inphotons and active neutrinos through cancellation with a new physics diagram.Both the Dodelson-Widrow and the Shi-Fuller mechanisms for sterile neutrinodark matter production are considered. As a final exotic example, potentialconsequences of CPT violation are discussed.<br

Systematic approach to leptogenesis in nonequilibrium QFT: vertex contribution to the CP-violating parameter

The generation of a baryon asymmetry via leptogenesis is usually studied by means of classical kinetic equations whose applicability to processes in the hot and expanding early universe is questionable. The approximations implied by the state-of-the-art description can be tested in a first-principle approach based on nonequilibrium field theory techniques. Here, we apply the Schwinger-Keldysh/Kadanoff-Baym formalism to a simple toy model of leptogenesis. We find that, within the toy model, medium effects increase the vertex contribution to the CP-violating parameter. At high temperatures it is a few times larger than in vacuum and asymptotically reaches the vacuum value as the temperature decreases. Contrary to the results obtained earlier in the framework of thermal field theory, the corrections are only linear in the particle number densities. An important feature of the Kadanoff-Baym formalism is that it is free of the double-counting problem, i.e. no need for real intermediate state subtraction arises. In particular, this means that the structure of the equations automatically ensures that the asymmetry vanishes in equilibrium. These results give a first glimpse into a number of new and interesting effects that can be studied in the framework of nonequilibrium field theory.Comment: 27 pages, 21 figure

Comparison of Boltzmann Equations with Quantum Dynamics for Scalar Fields

Boltzmann equations are often used to study the thermal evolution of particle reaction networks. Prominent examples are the computation of the baryon asymmetry of the universe and the evolution of the quark-gluon plasma after relativistic heavy ion collisions. However, Boltzmann equations are only a classical approximation of the quantum thermalization process which is described by the so-called Kadanoff-Baym equations. This raises the question how reliable Boltzmann equations are as approximations to the full Kadanoff-Baym equations. Therefore, we present in this paper a detailed comparison between the Kadanoff-Baym and Boltzmann equations in the framework of a scalar Phi^4 quantum field theory in 3+1 space-time dimensions. The obtained numerical solutions reveal significant discrepancies in the results predicted by both types of equations. Apart from quantitative discrepancies, on a qualitative level the universality respected by the Kadanoff-Baym equations is severely restricted in the case of Boltzmann equations. Furthermore, the Kadanoff-Baym equations strongly separate the time scales between kinetic and chemical equilibration. This separation of time scales is absent for the Boltzmann equation.Comment: text and figures revised, references added, results unchanged, 21 pages, 10 figures, published in Phys. Rev. D73 (2006) 12500

Dynamical Gauge Symmetry Breaking in SU(3)L⊗U(1)XSU(3)_L\otimes U(1)_X Extension of the Standard Model

We study the $SU(3)_L\otimes U(1)_X$ extension of the Standard model with a strong U(1) coupling. We argue that current experiments limit this coupling to be relatively large. The model is dynamically broken to the Standard $SU(2)_L \otimes U(1)$ model at the scale of a few TeV with all the extra gauge bosons and the exotic quarks acquiring masses much larger than the scale of electroweak symmetry breaking. Furthermore we find that the model leads to large dynamical mass of the top quark and hence also breaks the electroweak gauge symmetry. It therefore leads to large dynamical effects within the Standard model and can partially replace the Higgs interactions.Comment: 4 pages, revtex, no figures; revised version predicting realistic mass spectru

Leptogenesis with Dirac Neutrinos

We describe a "neutrinogenesis" mechanism whereby, in the presence of right-handed neutrinos with sufficiently small pure Dirac masses, (B+L)-violating sphaleron processes create the baryon asymmetry of the Universe, even when B=L=0 initially. It is shown that the resulting neutrino mass constraints are easily fulfilled by the neutrino masses suggested by current experiments. We present a simple toy model which uses this mechanism to produce the observed baryon asymmetry of the Universe. (PostScript Errors corrected in latest Version).Comment: 4 pages, Latex (using amsmath,feynmp,graphicx), 4 figure

Higher Dimensional Operators in Top Condensation from a Renormalization Group Point of View

The predictive power of top-condensation models strongly depends on the behaviour of higher dimensional operators. These are analyzed in this paper by an extension of the standard renormalization group (RG) arguments which turns out to be a surprisingly powerful tool. Top-condensation models intermediated by underlying scalar exchange can be shown to be mere reparametrizations of the standard model. Further on, RG-arguments show that dynamical vector states cannot be lowered in top-condensation models. Finally we give a general argument concerning the size of higher dimensional operators of heavy vector exchange.Comment: 21 pages, latex2e, axodraw.sty, epsfig.sty, 4 postscript figures. Some of the discussions extended and clarifie

Anomalous diffusion in viscosity landscapes

Anomalous diffusion is predicted for Brownian particles in inhomogeneous viscosity landscapes by means of scaling arguments, which are substantiated through numerical simulations. Analytical solutions of the related Fokker-Planck equation in limiting cases confirm our results. For an ensemble of particles starting at a spatial minimum (maximum) of the viscous damping we find subdiffusive (superdiffusive) motion. Superdiffusion occurs also for a monotonically varying viscosity profile. We suggest different substances for related experimental investigations.Comment: 15 page

Attosecond double-slit experiment

A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (``slits'') of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are observed. A situation in which one and the same electron encounters a single and a double slit at the same time is discussed. The investigation of the fringes makes possible interferometry on the attosecond time scale. The number of visible fringes, for example, indicates that the slits are extended over about 500as.Comment: 4 figure

Provably weak instances of ring-LWE revisited

In CRYPTO 2015, Elias, Lauter, Ozman and Stange described an attack on the non-dual decision version of the ring learning with errors problem (RLWE) for two special families of defining polynomials, whose construction depends on the modulus q that is being used. For particularly chosen error parameters, they managed to solve non-dual decision RLWE given 20 samples, with a success rate ranging from 10% to 80%. In this paper we show how to solve the search version for the same families and error parameters, using only 7 samples with a success rate of 100%. Moreover our attack works for every modulus q instead of the q that was used to construct the defining polynomial. The attack is based on the observation that the RLWE error distribution for these families of polynomials is very skewed in the directions of the polynomial basis. For the parameters chosen by Elias et al. the smallest errors are negligible and simple linear algebra suffices to recover the secret. But enlarging the error paremeters makes the largest errors wrap around, thereby turning the RLWE problem unsuitable for cryptographic applications. These observations also apply to dual RLWE, but do not contradict the seminal work by Lyubashevsky, Peikert and Regev

Collective dynamics of two-mode stochastic oscillators

We study a system of two-mode stochastic oscillators coupled through their collective output. As a function of a relevant parameter four qualitatively distinct regimes of collective behavior are observed. In an extended region of the parameter space the periodicity of the collective output is enhanced by the considered coupling. This system can be used as a new model to describe synchronization-like phenomena in systems of units with two or more oscillation modes. The model can also explain how periodic dynamics can be generated by coupling largely stochastic units. Similar systems could be responsible for the emergence of rhythmic behavior in complex biological or sociological systems.Comment: 4 pages, RevTex, 5 figure