Chargino Production and Decay in Photon-Photon-Collisions

We discuss the pair production of charginos in collisions of polarized photons $\gamma\gamma \to \tilde{\chi}_i^+ \tilde{\chi}_i^-$, ($i=1,2$) and the subsequent leptonic decay of the lighter chargino $\tilde{\chi}_1^+ \to \tilde{\chi}_1^0 e^+ \nu_e$ including the complete spin correlations. Analytical formulae are given for the polarization and the spin-spin correlations of the charginos. Since the production is a pure QED process the decay dynamics can be studied separately. For high energy photons from Compton backscattering of polarized laser pulses off polarized electron beams numerical results are presented for the cross section, the angular distribution and the forward-backward asymmetry of the decay positron. Finally we study the dependence on the gaugino mass parameter $M_1$ and on the sneutrino mass for a gaugino-like MSSM scenario.Comment: 22 pages, 15 figures, version to be published in Eur. Phys. J.

Estimating Drift Parameters in a Fractional Ornstein Uhlenbeck Process with Periodic Mean

We construct a least squares estimator for the drift parameters of a fractional Ornstein Uhlenbeck process with periodic mean function and long range dependence. For this estimator we prove consistency and asymptotic normality. In contrast to the classical fractional Ornstein Uhlenbeck process without periodic mean function the rate of convergence is slower depending on the Hurst parameter $H$, namely $n^{1-H}$

Risk Taking with Additive and Multiplicative Background Risks

We examine the effects of background risks on optimal portfolio choice. Examples of background risks include uncertain labor income, uncertainty about the terminal value of fixed assets such as housing and uncertainty about future tax liabilities. While some of these risks are additive and have been amply studied, others are multiplicative in nature and have received far less attention. The simultaneous effect of both additive and multiplicative risks has hitherto not received attention and can explain some paradoxical choice behavior. We rationalize such behavior and show how background risks might lead to seemingly U-shaped relative risk aversion for a representative investor.Derived risk aversion, Additive, multiplicative background risk

Multiplicative Background Risk

Although there has been much attention in recent years on the effects of additive background risks, the same is not true for its multiplicative counterpart. We consider random wealth of the multiplicative form xy, where x and y are statistically independent random variables. We assume that x is endogenous to the economic agent, but that y is an exogenous and nontradable background risk, which represents a type of market incompleteness. Our main focus is on how the presence of the multiplicative background risk y affects risk-taking behavior for decisions on the choice of x. We characterize conditions on preferences that lead to more cautious behavior.multiplicative risks, background risk, incomplete markets, standard risk aversion, affiliated utility function, multiplicative risk vulnerability

Multiplicative background risk

We consider random wealth of the multiplicative form xy, where x and y are statistically independent random variables. We assume that x is endogenous to the economic agent, but that y is an exogenous and uninsurable background risk. Our main focus is on how the randomness of y affects risk-taking behavior for decisions on the choice of x. We characterize conditions on preferences that lead to more cautious behavior. We also develop the concept of the affiliated utility function, which we define as the composition of the underlying utility function and the exponential function. This allows us to adapt several results for additive background risk to the multiplicative case. -- Wir betrachten den zufälligen Reichtum der multiplikativen Form xy, wo x und y statistisch unabhängige Zufallsvariablen sind. Wir nehmen an, daß x endogen für den ökonomischen Agenten ist, aber daß y ein exogenes und nicht versicherbares Hintergrundrisiko ist. Unser Hauptaugenmerk liegt darauf, wie die Zufälligkeit von y das Risikoverhalten bei Entscheidungen für x beeinflußt. Wir charakterisieren die Bedingungen der Präferenzen, die zu einem vorsichtigeren Verhalten führen. Wir entwickeln auch ein Konzept der „affiliated“ Nutzenfunktion, die eine Zusammensetzung der ursprünglichen Nutzenfunktion und der Exponentialfunktion ist. Dies erlaubt es uns, mehrere Ergebnisse für additive Hintergrundrisiken auf den multiplikativen Fall anzupassen.background risk,standard risk aversion,affiliated utility function

Multi-field modelling and simulation of large deformation ductile fracture

In the present contribution we focus on a phase-field approach to ductile fracture applied to large deformation contact problems. Phase-field approaches to fracture allow for an efficient numerical investigation of complex three-dimensional fracture problems, as they arise in contact and impact situations. To account for large deformations the underlying formulation is based on a multiplicative decomposition of the deformation gradient into an elastic and plastic part. Moreover, we make use of a fourth-order crack regularization combined with gradient plasticity. Eventually, a demonstrative example shows the capability of the proposed framework

Zero-mode contribution to the light-front Hamiltonian of Yukawa type models

Light-front Hamiltonian for Yukawa type models is determined without the framework of canonical light-front formalism. Special attention is given to the contribution of zero modes.Comment: 14 pages, Latex, revised version with minor changes, Submitted to J.Phys.