Search results for "METHODOLOGIE"
showing 10 items of 2141 documents
Shock capturing methods in 1D numerical relativity
2008
A numerical code is presented which uses modern shock capturing methods to evolve spherically symmetric perfect fluid space-times. Harmonic slicing is used to ensure singularity avoidance, which is crucial in strong field situations. Some tests are presented, including an application to the stellar collapse problem.
The $\varepsilon$-form of the differential equations for Feynman integrals in the elliptic case
2018
Feynman integrals are easily solved if their system of differential equations is in $\varepsilon$-form. In this letter we show by the explicit example of the kite integral family that an $\varepsilon$-form can even be achieved, if the Feynman integrals do not evaluate to multiple polylogarithms. The $\varepsilon$-form is obtained by a (non-algebraic) change of basis for the master integrals.
Functional and local renormalization groups
2015
We discuss the relation between functional renormalization group (FRG) and local renormalization group (LRG), focussing on the two dimensional case as an example. We show that away from criticality the Wess-Zumino action is described by a derivative expansion with coefficients naturally related to RG quantities. We then demonstrate that the Weyl consistency conditions derived in the LRG approach are equivalent to the RG equation for the $c$-function available in the FRG scheme. This allows us to give an explicit FRG representation of the Zamolodchikov-Osborn metric, which in principle can be used for computations.
RG flows of Quantum Einstein Gravity in the linear-geometric approximation
2014
We construct a novel Wetterich-type functional renormalization group equation for gravity which encodes the gravitational degrees of freedom in terms of gauge-invariant fluctuation fields. Applying a linear-geometric approximation the structure of the new flow equation is considerably simpler than the standard Quantum Einstein Gravity construction since only transverse-traceless and trace part of the metric fluctuations propagate in loops. The geometric flow reproduces the phase-diagram of the Einstein-Hilbert truncation including the non-Gaussian fixed point essential for Asymptotic Safety. Extending the analysis to the polynomial $f(R)$-approximation establishes that this fixed point come…
Search for new physics using QUAERO: A general interface to D0 Event data
2001
We describe Quaero, a method that i) enables the automatic optimization of searches for physics beyond the standard model, and ii) provides a mechanism for making high energy collider data generally available. We apply Quaero to searches for standard model WW, ZZ, and ttbar production, and to searches for these objects produced through a new heavy resonance. Through this interface, we make three data sets collected by the D0 experiment at sqrt(s)=1.8 TeV publicly available.
Single-shot color digital holography based on the fractional Talbot effect
2011
We present a method for recording on-axis color digital holograms in a single shot. Our system performs parallel phase-shifting interferometry by using the fractional Talbot effect for every chromatic channel simultaneously. A two-dimensional binary amplitude grating is used to generate Talbot periodic phase distributions in the reference beam. The interference patterns corresponding to the three chromatic channels are captured at once at different axial distances. In this scheme, one-shot recording and digital reconstruction allow for real-time measurement. Computer simulations and experimental results confirm the validity of our method.
The DEPFET pixel detector for the Belle II experiment at Super KEKB
2014
A pixel detector built with the DEPFET technology will be used for the two innermost layers of the Belle II experiment at the e + e SuperKEKB collider at KEK. The physics goals of the experiment impose challenging requirements to the design of the pixel detector in terms of performance, material budget and power consumption. The DEPFET technology has proven to be a suitable solution for the Belle II requirements and has been chosen as the baseline for the detector. This paper reviews the DEPFET pixel detector for Belle II and the various system aspects that have driven its final design.
Computational imaging with single-pixel detection: Applications in scattering media
2014
We describe computational imaging techniques based on single-pixel detection providing multidimensional information of an input scene. The key element of the optical recording stage is a spatial light modulator which sequentially generates a set of intensity light patterns to sample the scene. In this way, it is possible to use single-pixel detectors to measure different optical parameters such as the light intensity, the spectral content, the polarization state, or the phase. The spatial distribution of these parameters is then computed by applying the theory of compressive sampling. In particular, in this contribution we present a new method to transmit images through scattering media. We…
Optical module for single-shot quantitative phase imaging based on the transport of intensity equation with field of view multiplexing
2021
We present a cost-effective, simple, and robust method that enables single-shot quantitative phase imaging (QPI) based on the transport of intensity equation (TIE) using an add-on optical module that can be assembled into the exit port of any regular microscope. The module integrates a beamsplitter (BS) cube (placed in a non-conventional way) for duplicating the output image onto the digital sensor (field of view – FOV – multiplexing), a Stokes lens (SL) for astigmatism compensation (introduced by the BS cube), and an optical quality glass plate over one of the FOV halves for defocusing generation (needed for single-shot TIE algorithm). Altogether, the system provides two laterally separate…
Pattern projection for subpixel resolved imaging in microscopy.
2006
In this paper, we present a new approach providing super resolved images exceeding the geometrical limitation given by the detector pixel size of the imaging camera. The concept involves the projection of periodic patterns on top of the sample, which are then investigated under a microscope. Combining spatial scanning together with proper digital post-processing algorithm yields the improved geometrical resolution enhancement. This new method is especially interesting for microscopic imaging when the resolution of the detector is lower than the resolution due to diffraction.