Cross-section Fluctuations in Open Microwave Billiards and Quantum Graphs: The Counting-of-Maxima Method Revisited

The fluctuations exhibited by the cross-sections generated in a compound-nucleus reaction or, more generally, in a quantum-chaotic scattering process, when varying the excitation energy or another external parameter, are characterized by the width Gamma_corr of the cross-section correlation function. In 1963 Brink and Stephen [Phys. Lett. 5, 77 (1963)] proposed a method for its determination by simply counting the number of maxima featured by the cross sections as function of the parameter under consideration. They, actually, stated that the product of the average number of maxima per unit energy range and Gamma_corr is constant in the Ercison region of strongly overlapping resonances. We use the analogy between the scattering formalism for compound-nucleus reactions and for microwave resonators to test this method experimentally with unprecedented accuracy using large data sets and propose an analytical description for the regions of isolated and overlapping resonances

Residual stress development and evolution in two-phase crystalline material: a discrete dislocation study

Crystalline materials undergo heterogeneous deformation upon the application of external load, which results in the development of incompatible elastic strains in the material as soon as the load is removed. The presence of heterogeneous distribution of elastic strains in the absence of any form of external load results in the building up of stresses referred to as residual stresses. The heterogeneity of strain is attributed either to the presence of multiple phases or to the orientation gradients across the sample volume. This paper is an endeavour to model the presence of second phase in a two-dimensional discrete dislocation dynamics framework, which already contains constitutive rules to include three-dimensional mechanisms, such as line tension and dynamic junction formation. The model is used to investigate residual stress development in single crystals subjected to plane strain loading and then subsequently unloaded to study residual stresses. The dislocation accumulation around the second phase and its effect on the mechanical properties is studied. The orientation dependence of residual stresses as a function of the underlying defect substructure has also been explored. A variety of results are obtained. In particular, the development of stresses as a function of underlying defect substructure is also presented and found to depend upon the orientation of the crystal

Quantum and classical coarsening and their interplay with the Kibble-Zurek mechanism

Understanding the out-of-equilibrium dynamics of a closed quantum system driven across a quantum phase transition is an important problem with widespread implications for quantum state preparation and adiabatic algorithms. While the quantum Kibble-Zurek mechanism elucidates part of these dynamics, the subsequent and significant coarsening processes lie beyond its scope. Here, we develop a universal description of such coarsening dynamics -- and their interplay with the Kibble-Zurek mechanism -- in terms of scaling theories. Our comprehensive theoretical framework applies to a diverse set of ramp protocols and encompasses various coarsening scenarios involving both quantum and thermal fluctuations. Moreover, we highlight how such coarsening dynamics can be directly studied in today's "synthetic" quantum many-body systems, including Rydberg atom arrays, and present a detailed proposal for their experimental observation.Comment: 10 pages, 4 figure

Biases in parameter estimation from overlapping gravitational-wave signals in the third generation detector era

In the past few years, the detection of gravitational waves from compact binary coalescences with the Advanced LIGO and Advanced Virgo detectors has become routine. Future observatories will detect even larger numbers of gravitational-wave signals, which will also spend a longer time in the detectors' sensitive band. This will eventually lead to overlapping signals, especially in the case of Einstein Telescope (ET) and Cosmic Explorer (CE). Using realistic distributions for the merger rate as a function of redshift as well as for component masses in binary neutron star and binary black hole coalescences, we map out how often signal overlaps of various types will occur in an ET-CE network over the course of a year. We find that a binary neutron star signal will typically have tens of overlapping binary black hole and binary neutron star signals. Moreover, it will happen up to tens of thousands of times per year that two signals will have their end times within seconds of each other. In order to understand to what extent this would lead to measurement biases with current parameter estimation methodology, we perform injection studies with overlapping signals from binary black hole and/or binary neutron star coalescences. Varying the signal-to-noise ratios, the durations of overlap, and the kinds of overlapping signals, we find that in most scenarios the intrinsic parameters can be recovered with negligible bias. However, biases do occur for a short binary black hole or a quieter binary neutron star signal overlapping with a long and louder binary neutron star event when the merger times are sufficiently close. Hence our studies show where improvements are required to ensure reliable estimation of source parameters for all detected compact binary signals as we go from second-generation to third-generation detectors

Parameter estimation methods for analyzing overlapping gravitational wave signals in the third-generation detector era

In the coming years, third-generation detectors such as the EinsteinTelescope and the Cosmic Explorer will enter the network of ground-basedgravitational-wave detectors. Their current design predicts a significantlyimproved sensitivity band with a lower minimum frequency than existingdetectors. This, combined with the increased arm length, leads to two majoreffects: the detection of more signals and the detection of longer signals.Both will result in a large number of overlapping signals. It has been shown that such overlapping signals can lead to biases in therecovered parameters, which would adversely affect the science extracted fromthe observed binary merger signals. In this work, we analyze overlapping binaryblack hole coalescences with two methods to analyze multi-signal observations:hierarchical subtraction and joint parameter estimation. We find that thesemethods enable a reliable parameter extraction in most cases and that jointparameter estimation is usually more precise but comes with highercomputational costs.<br

Fracture surface characterization of epoxy-based GFRP laminates

Fractographic investigation has been carried out on glass fabric-epoxy composite laminates using scanning electron microscopy. Focusing on the flexural failure of lap shear specimens, some unique fracture features have been identified, and their likely origin suggested and explained. The influence of voids, present in the matrix, on the appearance of the fracture surface has been illustrated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44706/1/10853_2004_Article_BF00576775.pd

A morphology-independent search for gravitational wave echoes in data from the first and second observing runs of Advanced LIGO and Advanced Virgo

Theoretical Physic

Atom-efficient synthesis of a benchmark electrolyte for magnesium battery applications

The benchmark magnesium electrolyte, [Mg2Cl3]+ [AlPh4]−, can be prepared in a 100% atom-economic fashion by a ligand exchange reaction between AlCl3 and two molar equivalents of MgPh2. NMR and vibrational spectroscopy indicate that the reported approach results in a simpler ionic composition than the more widely adopted synthesis route of combining PhMgCl with AlCl3. Electrochemical performance has been validated by polarisation tests and cyclic voltammetry, which demonstrate excellent stability of electrolytes produced via this atom-efficient approach