0000000000131766

AUTHOR

Stefan Geiss

Framing Scandals: Cognitive and Emotional Media Effects

When covering violations of social norms by public figures, the mass media depict the resulting damages and attribute responsibility to actors. These depictions of responsibility constitute frames that elicit reactions from recipients. A theory regarding the effects of these media frames on cognitions, emotions, and opinions is presented. Content analyses of the media coverage of four cases and corresponding surveys were conducted. The findings indicate that the cognitions, emotions, and opinions of recipients cannot be sufficiently explained by learning of media input; recipients process the content based on individual frames. They complement fragmentary media frames and generate consisten…

research product

On an approximation problem for stochastic integrals where random time nets do not help

Abstract Given a geometric Brownian motion S = ( S t ) t ∈ [ 0 , T ] and a Borel measurable function g : ( 0 , ∞ ) → R such that g ( S T ) ∈ L 2 , we approximate g ( S T ) - E g ( S T ) by ∑ i = 1 n v i - 1 ( S τ i - S τ i - 1 ) where 0 = τ 0 ⩽ ⋯ ⩽ τ n = T is an increasing sequence of stopping times and the v i - 1 are F τ i - 1 -measurable random variables such that E v i - 1 2 ( S τ i - S τ i - 1 ) 2 ∞ ( ( F t ) t ∈ [ 0 , T ] is the augmentation of the natural filtration of the underlying Brownian motion). In case that g is not almost surely linear, we show that one gets a lower bound for the L 2 -approximation rate of 1 / n if one optimizes over all nets consisting of n + 1 stopping time…

research product

On fractional smoothness and Lp-approximation on the Wiener space

research product

Interpolation and approximation in L2(γ)

AbstractAssume a standard Brownian motion W=(Wt)t∈[0,1], a Borel function f:R→R such that f(W1)∈L2, and the standard Gaussian measure γ on the real line. We characterize that f belongs to the Besov space B2,qθ(γ)≔(L2(γ),D1,2(γ))θ,q, obtained via the real interpolation method, by the behavior of aX(f(X1);τ)≔∥f(W1)-PXτf(W1)∥L2, where τ=(ti)i=0n is a deterministic time net and PXτ:L2→L2 the orthogonal projection onto a subspace of ‘discrete’ stochastic integrals x0+∑i=1nvi-1(Xti-Xti-1) with X being the Brownian motion or the geometric Brownian motion. By using Hermite polynomial expansions the problem is reduced to a deterministic one. The approximation numbers aX(f(X1);τ) can be used to descr…

research product

Donsker-Type Theorem for BSDEs: Rate of Convergence

In this paper, we study in the Markovian case the rate of convergence in Wasserstein distance when the solution to a BSDE is approximated by a solution to a BSDE driven by a scaled random walk as introduced in Briand, Delyon and Mémin (Electron. Commun. Probab. 6 (2001) Art. ID 1). This is related to the approximation of solutions to semilinear second order parabolic PDEs by solutions to their associated finite difference schemes and the speed of convergence. peerReviewed

research product

Allern, Sigurd and Pollack, Ester (Eds.) (2012). Scandalous! The Mediated Construction of Political Scandals in Four Nordic Countries.

research product

AbsolutelyLexpq - Summing Norms of Diagonal Operators inlr and Limit Orders ofLexp - Summing Operators

We compute the absolutely L – summing norms of the diagonal operators acting on lr (1 ≤ q, r < ∞) and determine the limit orders of the absolutely Lexp – summing operators.

research product

A remark on extrapolation of rearrangement operators on dyadic Hs, 0&lt; s ≤1

research product

Haar Type and Carleson Constants

For a collection ℰ of dyadic intervals, a Banach space X, and p∈(1, 2], we assume the upper l p estimates where x I ∈X, and h I denotes the L ∞ normalized Haar function supported on I. We determine the minimal requirement on the size of ℰ such that these estimates imply that X is of Haar type p. The characterization is given in terms of the Carleson constant of ℰ.

research product

On singular integral and martingale transforms

Linear equivalences of norms of vector-valued singular integral operators and vector-valued martingale transforms are studied. In particular, it is shown that the UMD(p)-constant of a Banach space X equals the norm of the real (or the imaginary) part of the Beurling-Ahlfors singular integral operator, acting on the X-valued L^p-space on the plane. Moreover, replacing equality by a linear equivalence, this is found to be the typical property of even multipliers. A corresponding result for odd multipliers and the Hilbert transform is given.

research product

Interpolation and approximation in L2(γ)

Assume a standard Brownian motion W=(W"t)"t"@?"["0","1"], a Borel function f:R->R such that f(W"1)@?L"2, and the standard Gaussian measure @c on the real line. We characterize that f belongs to the Besov space B"2","q^@q(@c)@?(L"2(@c),D"1","2(@c))"@q","q, obtained via the real interpolation method, by the behavior of a"X(f(X"1);@t)@[email protected]?f(W"1)-P"X^@tf(W"1)@?"L"""2, where @t=(t"i)"i"="0^n is a deterministic time net and P"X^@t:L"2->L"2 the orthogonal projection onto a subspace of 'discrete' stochastic integrals x"[email protected]?"i"="1^nv"i"-"1(X"t"""i-X"t"""i"""-"""1) with X being the Brownian motion or the geometric Brownian motion. By using Hermite polynomial expansions the…

research product

On decoupling in Banach spaces

AbstractWe consider decoupling inequalities for random variables taking values in a Banach space X. We restrict the class of distributions that appear as conditional distributions while decoupling and show that each adapted process can be approximated by a Haar-type expansion in which only the pre-specified conditional distributions appear. Moreover, we show that in our framework a progressive enlargement of the underlying filtration does not affect the decoupling properties (in particular, it does not affect the constants involved). As a special case, we deal with one-sided moment inequalities for decoupled dyadic (i.e., Paley–Walsh) martingales and show that Burkholder–Davis–Gundy-type in…

research product

Permutation invariant functionals of Lévy processes

research product

Grassroots-Demokratie via Twitter?

„Was lange gart, wird endlich Wut.“Mit diesem umformulierten Sprichwort lasst sich die Entwicklung der Proteste um Stuttgart 21 (S21) treffend charakterisieren. Das Projekt ist eines der umstrittensten Verkehrs- und Stadtebauprojekte in Deutschland und beschaftigt die Bevolkerung – insbesondere die Stuttgarter Burger – seit Jahrzehnten: Zum einen soll der bestehende Kopfbahnhof in einen Durchgangsbahnhof sowie die Neubaustrecke zwischen Wendlungen und Ulm ausgebaut und zum anderen sollen durch die Umwandlung des Hauptbahnhofs freiwerdende Gleisstrecken stadtebaulich verandert werden. Bereits in den 1980er Jahren gab es hierzu erste Beratungen und Plane auf Bundes- und Landesebene. In einem …

research product

Decoupling on the Wiener Space, Related Besov Spaces, and Applications to BSDEs

We introduce a decoupling method on the Wiener space to define a wide class of anisotropic Besov spaces. The decoupling method is based on a general distributional approach and not restricted to the Wiener space. The class of Besov spaces we introduce contains the traditional isotropic Besov spaces obtained by the real interpolation method, but also new spaces that are designed to investigate backwards stochastic differential equations (BSDEs). As examples we discuss the Besov regularity (in the sense of our spaces) of forward diffusions and local times. It is shown that among our newly introduced Besov spaces there are spaces that characterize quantitative properties of directional derivat…

research product

Weighted bounded mean oscillation applied to backward stochastic differential equations

Abstract We deduce conditional L p -estimates for the variation of a solution of a BSDE. Both quadratic and sub-quadratic types of BSDEs are considered, and using the theory of weighted bounded mean oscillation we deduce new tail estimates for the solution ( Y , Z ) on subintervals of [ 0 , T ] . Some new results for the decoupling technique introduced in Geiss and Ylinen (2019) are obtained as well and some applications of the tail estimates are given.

research product

On approximation of a class of stochastic integrals and interpolation

Given a diffusion Y = (Y_{t})_{t \in [0,T]} we give different equivalent conditions so that a stochastic integral has an L 2-approximation rate of n −η, {\rm \eta \in (0,1/2],} if one approximates by integrals over piece-wise constant integrands where equidistant time nets of cardinality n + 1 are used. In particular, we obtain assertions in terms of smoothness properties of g(Y T ) in the sense of Malliavin calculus. After optimizing over non-equidistant time-nets of cardinality n + 1 in case {\rm \eta > 0} , it turns out that one always obtains a rate of n^{ - 1/2}, which is optimal. This applies to all functions g obtained in an appropriate way by the real interpolation method between th…

research product

Quantitative approximation of certain stochastic integrals

We approximate certain stochastic integrals, typically appearing in Stochastic Finance, by stochastic integrals over integrands, which are path-wise constant within deterministic, but not necessarily equidistant, time intervals. We ask for rates of convergence if the approximation error is considered in L 2 . In particular, we show that by using non-equidistant time nets, in contrast to equidistant time nets, approximation rates can be improved considerably.

research product