1,357 research outputs found
Exact wave-optical imaging of a Kerr-de Sitter black hole using Heun's equation
Spacetime perturbations due to scalar, vector, and tensor fields on a fixed
background geometry can be described in the framework of Teukolsky's equation.
In this work, wave scattering is treated analytically, using the Green's
function method and solutions to the separated radial and angular differential
equations in combination with a partial wave technique for a scalar and
monochromatic perturbation. The results are applied to analytically describe
wave-optical imaging via Kirchhoff-Fresnel diffraction, leading to, e.g., the
formation of observable black hole shadows. A comparison to the ray-optical
description is given, providing new insights into wave-optical effects and
properties. On a Kerr-de Sitter spacetime, the cosmological constant changes
the singularity structure of the Teukolsky equation and allows for an
analytical, exact solution via a transformation into the Heun's differential
equation, which is the most general, second-order differential equation with
four regular singularities. The scattering of waves originating from a point
source involves a solution in terms of the so-called Heun's function . It
is used to find angular solutions, which form a complete set of orthonormal
functions similar to the spherical harmonics. Our approach allows to solve the
scattering problem while taking into account the complex interplay of Heun's
functions around local singularities.Comment: 27 pages, 15 figure
Nonlinear Spectroscopy and All-Optical Switching of Femtosecond Soliton Molecules
The emergence of confined structures and pattern formation are exceptional
manifestations of concurring nonlinear interactions found in a variety of
physical, chemical and biological systems[1]. Optical solitons are a hallmark
of extreme spatial or temporal confinement enabled by a variety of
nonlinearities. Such particle-like structures can assemble in complex stable
arrangements, forming "soliton molecules"[2,3]. Recent works revealed
oscillatory internal motions of these bound states, akin to molecular
vibrations[4-8]. These observations beg the question as to how far the
"molecular" analogy reaches, whether further concepts from molecular
spectroscopy apply in this scenario, and if such intra-molecular dynamics can
be externally driven or manipulated. Here, we probe and control such ultrashort
bound-states in an optical oscillator, utilizing real-time spectroscopy and
time-dependent external perturbations. We introduce two-dimensional
spectroscopy of the linear and nonlinear bound-state response and resolve
anharmonicities in the soliton interaction leading to overtone and sub-harmonic
generation. Employing a non-perturbative interaction, we demonstrate
all-optical switching between distinct states with different binding
separation, opening up novel schemes of ultrafast spectroscopy, optical logic
operations and all-optical memory.Comment: 3 figure
House price expectations
This study examines short-, medium-, and long-run price expectations in housing markets. We derive and test six hypothesis about the incidence, formation, and relevance of price expectations. To do so, we use data from a tailored household survey, past sale offerings, satellites, and from an information RCT. As novel findings, we show that price expectations exhibit mean reversion in the long-run. Moreover, we do not find evidence for biases related to individual housing tenure decisions or regret aversion. Confirming existing findings, we show that local market characteristics matter for expectations throughout, as well as aggregate price information. Lastly, we corroborate existing evidence that expectations are relevant for portfolio choice
House Price Expectations
This study examines short-, medium-, and long-run price expectations in housing markets. We derive and test six hypothesis about the incidence, formation, and relevance of price expectations. To do so, we use data from a tailored household survey, past sale and rental offerings, satellites, and from an information RCT. As novel findings, we show that price expectations exhibit mean reversion in the long-run. Moreover, we do not find evidence for biases related to individual housing tenure decisions or regret aversion. Confirming existing findings, we show that local market characteristics matter for expectations throughout, as well as aggregate price information. Lastly, we corroborate existing evidence that expectations are relevant for portfolio choice
Planar n-in-n quad module prototypes for the ATLAS ITk upgrade at HL-LHC
In order to meet the requirements of the High Luminosity LHC (HL-LHC), it
will be necessary to replace the current tracker of the ATLAS experiment.
Therefore, a new all-silicon tracking detector is being developed, the
so-called Inner Tracker (ITk). The use of quad chip modules is intended in its
pixel region. These modules consist of a silicon sensor that forms a unit along
with four read-out chips. The current ATLAS pixel detector consists of planar
n-in-n silicon pixel sensors. Similar sensors and four FE-I4 read-out chips
were assembled to first prototypes of planar n-in-n quad modules. The main
focus of the investigation of these modules was the region between the read-out
chips, especially the central area between all four read-out chips. There are
special pixel cells placed on the sensor which cover the gap between the
read-out chips. This contribution focuses on the characterization of a
non-irradiated device, including important sensor characteristics, charge
collection determined with radioactive sources as well as hit efficiency
measurements, performed in the laboratory and at testbeams. In addition, first
laboratory results of an irradiated device are presented
Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules
We study the Strong-Field Ionization (SFI) of the hydrocarbon 1-butene as a function of wavelength using photoion-photoelectron covariance and coincidence spectroscopy. We observe a striking transition in the fragment-associated photoelectron spectra: from a single Above Threshold Ionization (ATI) progression for photon energies less than the cation D0âD1 gap to two ATI progressions for a photon energy greater than this gap. For the first case, electronically excited cations are created by SFI populating the ground cationic state D0, followed by sequential post-ionization excitation. For the second case, direct sub-cycle SFI to the D1 excited cation state contributes significantly. Our experiments access ionization dynamics in a regime where strong-field and resonance-enhanced processes can interplay
Structural Insight v3: A stand-alone program for micro structural analysis of computed tomography volumes
Structural Insight is a software for the analysis of 3D quantitative computed
tomography volumes with a special weight for the analysis of the trabecular microstructure of human vertebrae.Sociedad Argentina de InformĂĄtica e InvestigaciĂłn Operativa (SADIO
Structural Insight v3: A stand-alone program for micro structural analysis of computed tomography volumes
Structural Insight is a software for the analysis of 3D quantitative computed
tomography volumes with a special weight for the analysis of the trabecular microstructure of human vertebrae.Sociedad Argentina de InformĂĄtica e InvestigaciĂłn Operativa (SADIO
Interactive Quality Inspection of Measured Deviations in Sheet Metal Assemblies
We present an exploratory data analysis approach for finite element (FE) simulations to interactively inspect measured deviations in sheet metals arising in automotive applications. Exterior car body parts consist of large visible surfaces, and strict tolerances must be met by them to satisfy both aesthetic requirements and quality performance requirements. To fulfill quality requirements like gap and flushness, exterior vehicle components have adjustable mechanical boundaries. These boundaries are used to influence the shape and position of a sheet metal part relative to its chassis. We introduce a method that supports an inspection engineer with an interactive framework that makes possible a detailed analysis of measured sheet metal deviation fields generated from 3D scans. An engineer can interactively change boundary conditions and obtains the resulting deviation field in real-time. Thus, it is possible to determine viable and desirable adjustments efficiently, leading to time and cost savings in the assembly process
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