Pulsar timing arrays offer a probe of the low-frequency gravitational wave spectrum (1 - 100 nanohertz), which is intimately connected to a number of markers that can uniquely trace the formation and ...evolution of the Universe. We present the dataset and the results of the timing analysis from the second data release of the European Pulsar Timing Array (EPTA). The dataset contains high-precision pulsar timing data from 25 millisecond pulsars collected with the five largest radio telescopes in Europe, as well as the Large European Array for Pulsars. The dataset forms the foundation for the search for gravitational waves by the EPTA, presented in associated papers. We describe the dataset and present the results of the frequentist and Bayesian pulsar timing analysis for individual millisecond pulsars that have been observed over the last ~25 years. We discuss the improvements to the individual pulsar parameter estimates, as well as new measurements of the physical properties of these pulsars and their companions. This data release extends the dataset from EPTA Data Release 1 up to the beginning of 2021, with individual pulsar datasets with timespans ranging from 14 to 25 years. These lead to improved constraints on annual parallaxes, secular variation of the orbital period, and Shapiro delay for a number of sources. Based on these results, we derived astrophysical parameters that include distances, transverse velocities, binary pulsar masses, and annual orbital parallaxes.
•Si nanopyramids combined with Al metal nanoparticles for enhancing light harvesting capability.•Geometric Optimization is done using 3D finite-difference time-domain (FDTD) method.•The optimal ...values of the lattice constant, height and period between NPs as 60 nm, 150 nm and 60 nm respectively.•Jsc of 41.71 mA/cm2 is achievable which is ~44.47% higher than its planar counterpart.•PCE and FF of 11.32 and 78.02% is achieved with the optimized HSC structure.
In this article, we have investigated the combined role of nanopyramid (NP) array and metal nanoparticles (MNPs) in enhancing the light trapping ability and improving the photo-absorption of PEDOT:PSS/c-Si Hybrid Solar Cells (HSCs) using a 3D finite-difference time-domain (FDTD) method. A parametric optimization of the essential geometrical parameters of NPs and MNP is performed based on short circuit current density (Jsc). The optimization result reveals that maximum Jsc of 35.91 mA/cm2 is achievable with top textured NP (without MNPs) which is 24.38% higher than the planar counterpart. However, the absorption spectrum is broadened with the insertion of Al MNP at rear side of the HSC. This is also accompanied by almost two fold increase in Jsc to 41.71 mA/cm2 which is 44.47% higher the planar HSCs. The photovoltaic parameters such as Jsc, Voc, PCE and Fill Factor (FF) are calculated using the DEVICE software for NP and NP embedded with Al MNPs based c-Si Solar Cells. The physics at the interface of inorganic nanostructure and organic material layer is thoroughly described. In addition to this, we have tried to decode the underlying physics for the enhancement of photon absorption in nanopyramidal structures and MNPs structures through an extensive analysis of the photogeneration rate, electric field intensity, power absorption profiles, PCE and FF of nanopyramidal, nanopyramidal with MNP and planar HSCs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Gravitational waves emitted from the coalescence of neutron star binaries open a new window to probe matter and fundamental physics in unexplored, extreme regimes. To extract information about the ...supranuclear matter inside neutron stars and the properties of the compact binary systems, robust theoretical prescriptions are required. We give an overview about general features of the dynamics and the gravitational wave signal during the binary neutron star coalescence. We briefly describe existing analytical and numerical approaches to investigate the highly dynamical, strong-field region during the merger. We review existing waveform approximants and discuss properties and possible advantages and shortcomings of individual waveform models, and their application for real gravitational-wave data analysis.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Quantum spin liquids, exotic phases of matter with topological order, have been a major focus in physics for the past several decades. Such phases feature long-range quantum entanglement that can ...potentially be exploited to realize robust quantum computation. We used a 219-atom programmable quantum simulator to probe quantum spin liquid states. In our approach, arrays of atoms were placed on the links of a kagome lattice, and evolution under Rydberg blockade created frustrated quantum states with no local order. The onset of a quantum spin liquid phase of the paradigmatic toric code type was detected by using topological string operators that provide direct signatures of topological order and quantum correlations. Our observations enable the controlled experimental exploration of topological matter and protected quantum information processing.
Gravitational wave (GW) astronomy has consolidated its role as a new observational window to reveal the properties of compact binaries in the Universe. In particular, the discovery of the first ...binary neutron star coalescence, GW170817, led to a number of scientific breakthroughs as the possibility to place constraints on the equation of state of cold matter at supranuclear densities. These constraints and all scientific results based on them require accurate models describing the GW signal to extract the source properties from the measured signal. In this article, we study potential systematic biases during the extraction of parameters from non-spinning sources using different descriptions for both, the point-particle dynamics and tidal effects. We find that for the considered cases the mass and spin recovery show almost no systematic bias with respect to the chosen waveform model. However, the extracted tidal effects can be strongly biased, where we find generally that Post-Newtonian approximants predict neutron stars with larger deformability and radii than numerical relativity tuned models. Noteworthy, an increase in the post-Newtonian order in the tidal phasing does not lead to a monotonic change in the estimated properties. We find that for a signal with strength similar to GW170817, but observed with design sensitivity with the network of the two LIGO detectors and the Virgo detector, the estimated tidal parameters can differ by more than a factor of two depending on the employed tidal description of the waveform approximant. This shows the current need for the development of better waveform models to extract reliably the source properties from upcoming GW detections.
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One of the key downsides of modular multilevel converter (MMC) topology is the high expense on capacitors present in the submodules (SMs). Injection of circulating-currents calculated and stored in ...lookup tables to reduce SM capacitor voltage ripple is a popular practice since it allows smaller capacitors to be used. The arm energy deviation is essentially correlated to the SM capacitor-voltage deviation. In this article, a generalized decoupled double synchronous reference frame-based control framework is presented through which the arm energy deviations are optimized (minimized) using only instantaneous values of currents and voltages, as well as simple integral or proportional control. Furthermore, extensive analysis is provided to find a tradeoff between the energy deviation minimization and the arm current rms. The viability of the proposed capacitor voltage ripple optimization method is confirmed by simulation and experiment.
In this paper, we have analyzed the role of single and dual nanostructures embedded in PEDOT:PSS (Poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate))/c-Si Hybrid Solar Cells (HSCs) using ...Finite Difference Time Domain (FDTD) method. HSC structures with Nanopyramids (NPs) on top of the Si substrate exhibit optical Jsc of 35.91 mA/cm2. We obtained significant improvement in Jsc by 1.56% and 14% observed with the insertion of oxide coated Ag MNPs (Metal Nanoparticles) and Al MNPs in the rear and front end of the HSC, respectively. A comparative analysis of these three structures denoted as NP (for nanopyramids only), NP + Ag MNPs (nanopyramids with Ag MNPs embedded in the front end of the HSCs along with oxide coated MNPs in the rear end) and NP + Al MNPs (same as the second structure with Ag MNPs replaced with Al MNPs) shows that HSCs with NP + Ag MNPs and MoO3 coating achieve the highest open circuit voltage (Voc) of 0.7 V, electrical Jsc of 22.19 mA/cm2, power conversion efficiency (PCE) of 12.56% and Fill Factor (FF) of 80.85%.
•Role of nanostructures in PEDOT:PSS/c-Si solar cells studied using FDTD method.•Optimization of nanostructure done in terms of optical Jsc.•Jsc of 35.91 mA/cm2 obtained with Nanopyramids (NPs) on top of the Si substrate.•NPs with metal nanoparticles at rear and back end of Si exhibits best PCE.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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Quantum phases of Rydberg atoms on a kagome lattice Samajdar, Rhine; Ho, Wen Wei; Pichler, Hannes ...
Proceedings of the National Academy of Sciences - PNAS,
01/2021, Volume:
118, Issue:
4
Journal Article
Peer reviewed
Open access
We analyze the zero-temperature phases of an array of neutral atoms on the kagome lattice, interacting via laser excitation to atomic Rydberg states. Density-matrix renormalization group calculations ...reveal the presence of a wide variety of complex solid phases with broken lattice symmetries. In addition, we identify a regime with dense Rydberg excitations that has a large entanglement entropy and no local order parameter associated with lattice symmetries. From a mapping to the triangular lattice quantum dimer model, and theories of quantum phase transitions out of the proximate solid phases, we argue that this regime could contain one or more phases with topological order. Our results provide the foundation for theoretical and experimental explorations of crystalline and liquid states using programmable quantum simulators based on Rydberg atom arrays.
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