[en] We derive new improved constraints on the compactification scale of minimal 5-dimensional (5D) extensions of the Standard Model (SM) from electroweak and LEP2 data and estimate the reach of an e⁺e^- linear collider such as TESLA. Our analysis is performed within the framework of non-universal 5D models, where some of the gauge and Higgs fields propagate in the extra dimension, while all fermions are localized on a S¹/Z₂ orbifold fixed point. Carrying out simultaneous multi-parameter fits of the compactification scale and the SM parameters to the data, we obtain lower bounds on this scale in the range between 4 and 6 TeV. These fits also yield the correlation of the compactification scale with the SM Higgs mass. Investigating the prospects at TESLA, we show that the so-called GigaZ option has the potential to improve these bounds by about a factor 2 in almost all 5D models. Furthermore, at the center of mass energy of 800 GeV and with an integrated luminosity of 10³ fb^-1, linear collider experiments can probe compactification scales up to 20-30 TeV, depending on the control of systematic errors

[en] In supersymmetric extensions of the Standard Model, heavy Majorana neutrinos can generate lepton flavor violating slepton mass terms. These may give rise to observable rare decays like la>l?, and rare processes like la lalB+jets+ET at future colliders. Searches for these signal processes, combined with neutrino data and the hypothesis of leptogenesis, can impose strong constraints on the fundamental parameters of the underlying seesaw scenario

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[en] Supersymmetric extensions of warped higgsless models of electroweak symmetry breaking provide a dark matter candidate which naturally has a relic density compatible with recent observations. We find an extended particle spectrum which reflects the close relationship of N=1 SUSY in 5 dimensions with N=2 SUSY in four dimensions. Among the new states in the gauge multiplets are scalars with properties which add interesting aspects to the forthcoming Higgs searches at the LHC

[en] Kaluza and Klein proposed a framework based on four space dimensions to unify gravity and electromagnetism. Consistent superstring theories are formulated in 10 or 11 dimensions. Recently, quantum gauge theories have been studied in large extra space dimensions. I will discuss generic properties of extensions of the SU(3)xSU(2)xU(1) standard model to five dimensions

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[en] We derive the most general Seiberg-Witten maps for noncommutative gauge theories in second order of the noncommutative parameter θ. Our results reveal the existence of more ambiguities than previously known. In particular, we demonstrate that some of these ambiguities enter observables like scattering cross sections and enlarge the parameter space of the noncommutative standard model beyond O(θ)

[en] We study collider signals for the noncommutative extension of the standard model using the Seiberg-Witten maps for SU(3)_C(multiply-in-circle sign)SU(2)_LxU(1)_Y to first order in the noncommutativity parameters θ_μν. In particular, we investigate the sensitivity of Zγ-production at the Tevatron and the LHC to the components of θ_μν. We discuss the range of validity of this approximation and estimate exclusion limits from a Monte Carlo simulation

[en] We study Ward identities for simple processes with external gauge bosons in the time-ordered perturbation theory approach to time-like noncommutative gauge theories. We demonstrate that these Ward identities cannot be satisfied when all orders in the noncommutativity parameters θ_i0 are taken into account. We conclude that in time-ordered perturbation theory one cannot solve the unitarity problem of time-like noncommutative quantum field theories