119436002
Lepton flavor violating processes at the International Linear Collider
We study the effects of dimension-six effective operators on the flavor violating production and decay of leptons at the International Linear Collider. Analytic expressions for the cross sections, decay widths, and asymmetries of all flavor changing processes will be presented, as well as an analysis of the feasibility of their observation at the ILC.
119205906
Discrete and continuous symmetries in multi-Higgs-doublet models
We consider the Higgs sector of multi-Higgs-doublet models in the presence of simple symmetries relating the various fields. We construct basis-invariant observables which may in principle be used to detect these symmetries for any number of doublets. A categorization of the symmetries into classes is required, which we perform in detail for the case of two and three Higgs doublets.
118913042
Lepton Flavour Violation at the ILC
We explore the possibility of detecting lepton flavour violation, now a well established experimental fact, at the International Linear Collider. Using a model independent approach we conclude that, given all experimental constraints available, there is still room to detect lepton flavour violation at the ILC.
119493491
One-loop stau masses in the effective potential approach
We calculate the one-loop contributions to the tau slepton masses in the Minimal Supersymmetric Standard Model in the effective potential approach. For the majority of parameter space under study, those corrections are shown to elevate the value of the lightest stau mass.
117960699
The CP-conserving 2HDM after the 8 TeV run
We confront the most common CP-conserving 2HDM with the LHC data analysed so far while taking into account all previously available experimental data. A special allowed corner of the parameter space is analysed - the so-called wrong-sign scenario where the Higgs coupling to down-type quarks changes sign relative to the Standard Model while the coupling to the massive vector bosons does not.
119087524
Neutral minima in two-Higgs doublet models
We study the neutral minima of two-Higgs doublet models, showing that these potentials can have at least two such minima with different depths. We analyse the phenomenology of these minima for the several types of two-Higgs doublet potentials, where CP is explicitly broken, spontaneously broken or preserved. We discover that it is possible to have a neutral minimum in these potentials where the masses of the known particles have their standard values, with another deeper minimum where those same particles acquire different masses.
209833975
Does dark energy really exist
The article discusses the possibility that dark energy may not exist. The observations related to the expansion of the universe that caused scientists to initially infer its existence are noted. The alternative possibility that the Milky Way Galaxy lies in a giant cosmic void is also discussed, noting that scientists will make observations in the years following 2009 to determine which of the theories is correct. INSETS: COPERNICUS'S LEGACY;Three Ways of Expanding a Universe;A Special Place for Us;Surrender to the Void
119264670
Ultralight axions: degeneracies with massive neutrinos and forecasts for future cosmological observations
A generic prediction of string theory is the existence of many axion fields. It has recently been argued that many of these fields should be light and, like the well known QCD axion, lead to observable cosmological consequences. In this paper we study in detail the effect of the so-called string axiverse on large scale structure, focusing on the morphology and evolution of density perturbations, anisotropies in the cosmic microwave background and weak gravitational lensing of distant galaxies. We quantify specific effects that will arise from the presence of the axionic fields and highlight possible degeneracies that may arise in the presence of massive neutrinos. We take particular care understanding the different physical effects and scales that come into play. We then forecast how the string axiverse may be constrained and show that with a combination of different observations, it should be possible to detect a fraction of ultralight axions to dark matter of a few percent.
14689706
Microwave Anisotropies from Random Sources
I report on recent developments in the theory of cosmic background radiation perturbations. I describe ways of modeling alternatives to the canonical Gaussian theories within the standard framework of cosmological perturbation theory. Some comments are made on using these techniques to resolve the uncertainties in theories of structure formation with topological defects. (To appear in the proceedings of the XXXIth Moriond meeting, ``Microwave Background Anisotropies'')
15699329
Cumulants as non-Gaussian qualifiers
We discuss the requirements of good statistics for quantifying non-Gaussianity in the cosmic microwave background. The importance of rotational invariance and statistical independence is stressed, but we show that these are sometimes incompatible. It is shown that the first of these requirements prefers a real space (or wavelet) formulation, whereas the latter favors quantities defined in Fourier space. Bearing this in mind we decide to be eclectic and define two new sets of statistics to quantify the level of non-Gaussianity. Both sets make use of the concept of cumulants of a distribution. However, one set is defined in real space, with reference to the wavelet transform, whereas the other is defined in Fourier space. We derive a series of properties concerning these statistics for a Gaussian random field and show how one can relate these quantities to the higher order moments of temperature maps. Although our frameworks lead to an infinite hierarchy of quantities we show how cosmic variance and experimental constraints give a natural truncation of this hierarchy. We then focus on the real space statistics and analyze the non-Gaussian signal generated by point sources obscured by large scale Gaussian fluctuations. We conclude by discussing the practical implementations of these techniques.
54177748
Fast route to nonlinear clustering statistics in modified gravity theories
We propose a simple and computationally fast method for performing $N$-body simulations for a large class of modified gravity theories with a screening mechanism such as chameleons, symmetrons, and Galileons. By combining the linear Klein\char21{}Gordon equation with a screening factor, calculated from analytical solutions of spherical symmetric configurations, we obtain a modified field equation of which the solution is exact in the linear regime while at the same time taking screening into account on nonlinear scales. The resulting modified field equation remains linear and can be solved just as quickly as the Poisson equation without any of the convergence problems that can arise when solving the full equation. We test our method with $N$-body simulations and find that it compares remarkably well with full simulations well into the nonlinear regime.