470 research outputs found
Uncertainty in Crowd Data Sourcing under Structural Constraints
Applications extracting data from crowdsourcing platforms must deal with the
uncertainty of crowd answers in two different ways: first, by deriving
estimates of the correct value from the answers; second, by choosing crowd
questions whose answers are expected to minimize this uncertainty relative to
the overall data collection goal. Such problems are already challenging when we
assume that questions are unrelated and answers are independent, but they are
even more complicated when we assume that the unknown values follow hard
structural constraints (such as monotonicity).
In this vision paper, we examine how to formally address this issue with an
approach inspired by [Amsterdamer et al., 2013]. We describe a generalized
setting where we model constraints as linear inequalities, and use them to
guide the choice of crowd questions and the processing of answers. We present
the main challenges arising in this setting, and propose directions to solve
them.Comment: 8 pages, vision paper. To appear at UnCrowd 201
Longitudinal and transverse fermion-boson vertex in QED at finite temperature in the HTL approximation
We evaluate the fermion-photon vertex in QED at the one loop level in Hard
Thermal Loop approximation and write it in covariant form. The complete vertex
can be expanded in terms of 32 basis vectors. As is well known, the
fermion-photon vertex and the fermion propagator are related through a
Ward-Takahashi Identity (WTI). This relation splits the vertex into two parts:
longitudinal (Gamma_L) and transverse (Gamma_T). Gamma_L is fixed by the WTI.
The description of the longitudinal part consumes 8 of the basis vectors. The
remaining piece Gamma_T is then written in terms of 24 spin amplitudes.
Extending the work of Ball and Chiu and Kizilersu et. al., we propose a set of
basis vectors T^mu_i(P_1,P_2) at finite temperature such that each of these is
transverse to the photon four-momentum and also satisfies T^mu_i(P,P)=0, in
accordance with the Ward Identity, with their corresponding coefficients being
free of kinematic singularities. This basis reduces to the form proposed by
Kizilersu et. al. at zero temperature. We also evaluate explicitly the
coefficient of each of these vectors at the above-mentioned level of
approximation.Comment: 13 pages, uses RevTe
New physics with mirror particles
The introduction of mirror fermions with masses between the weak scale and 1
TeV could offer a dynamical origin to the standard-model electro-weak symmetry
breaking mechanism. The purpose of this work is to study the dynamics needed in
order to render models with such a fermion content phenomenologically
acceptable.Comment: 28 LaTeX pages, to appear in the Journal of Physics
Population genomics supports clona reproduction and multiple independent gains and losses of parasitic abilities in the most devastating nematode pest.
International audienc
Chiral Symmetry Breaking via Multi-fermion Green Functions
Previous results on fermion chirality-flipping four-point functions are
extended to gauge theories. The problem is purely non-perturbative, and
it is approached by truncating the Schwinger-Dyson hierarchy. The large-
limit also simplifies the problem substantially. The resulting equation is
solved numerically by relaxation techniques and an estimate of the critical
coupling and momentum behavior is obtained. We also comment on the behavior of
chirality-flipping -point functions for general .Comment: 17 pages, LaTeX + 3 figures, version to be publishe
- âŠ