Physics MDPI

📢 We are excited to share the good news that Physics MDPI received a new Impact Factor of 1.5, ranking Q2 in the "PHYSICS, MULTIDISCIPLINARY" category; new CiteScore of 3. 🎉 Thanks for the support of Editorial Board Members, reviewers and authors! MDPI; #OpenAccess #physics

Trends in the Structure of Nuclei near 100Sn | Review by Magdalena Górska https://lnkd.in/g9i7kfG2 GSI Helmholtz Centre for Heavy Ion Research; MDPI #Nuclei #nuclear #shellmodel #physics This article belongs to the Special Issue The Nuclear Shell Model 70 Years after Its Advent: Achievements and Prospects https://lnkd.in/dAtgbDyi #Abstract Inevitable progress has been achieved in recent years regarding the available data on the structure of 100Sn and neighboring nuclei. Updated nuclear structure data in the region is presented using selected examples. State-of-the-art experimental techniques involving stable and radioactive beam facilities have enabled access to those exotic nuclei. The analysis of experimental data has established the shell structure and its evolution towards N = Z = 50 of the number of neutrons, N, and the atomic number, Z, seniority conservation and proton–neutron interaction in the g9/2 orbit, the super-allowed Gamow–Teller decay of 100Sn, masses and half-lives along the rapid neutron-capture process (r-process) path and super-allowed α decay beyond 100Sn. The status of theoretical approaches in shell model and mean-field investigations are discussed and their predictive power assessed. The calculated systematics of high-spin states for N = 50 isotopes including the 5− state and N = Z nuclei in the g9/2 orbit is presented for the first time.

Ion Implantation into Nonconventional GaN Structures | Review by Katharina Lorenz https://lnkd.in/g6kgnfqb ULisboa; INESC；MDPI #group III nitrides; #non-polar #GaN; #nanowires; #ion #implantation; #doping #physics This article belongs to the Special Issue: Selected Papers from Applied Nuclear Physics Conference 2021 https://lnkd.in/ghJdaRhH #Abstract Despite more than two decades of intensive research, ion implantation in group III nitrides is still not established as a routine technique for doping and device processing. The main challenges to overcome are the complex defect accumulation processes, as well as the high post-implant annealing temperatures necessary for efficient dopant activation. This review summarises the contents of a plenary talk, given at the Applied Nuclear Physics Conference, Prague, 2021, and focuses on recent results, obtained at Instituto Superior Técnico (Lisbon, Portugal), on ion implantation into non-conventional GaN structures, such as non-polar thin films and nanowires. Interestingly, the damage accumulation is strongly influenced by the surface orientation of the samples, as well as their dimensionality. In particular, basal stacking faults are the dominant implantation defects in c-plane GaN films, while dislocation loops predominate in a-plane samples. Ion implantation into GaN nanowires, on the other hand, causes a much smaller density of extended defects compared to thin films. Finally, recent breakthroughs concerning dopant activation are briefly reviewed, focussing on optical doping with europium and electrical doping with magnesium.

#FeaturePaper Quantum Cryptography—A Simplified Undergraduate Experiment and Simulation | Article by Yuval Bloom, Ilai Fields, Alona Maslennikov and Georgi Gary Rozenman, Ph.D https://lnkd.in/gT3NeE8K Tel Aviv University; MDPI #Quantum #Cryptography #undergraduate #education #physics #Openaccess #Abstract Quantum cryptography is a topic of considerable interest. A simple and robust experiment and theory for a senior level undergraduate investigation of quantum key distribution are described. In the proposed experiment, key principles from the BB84 protocol, used in quantum cryptography, are emulated using an optical apparatus and computational scripts independently.

Dissipative Ion-Acoustic Solitary Waves in Magnetized κ-Distributed Non-Maxwellian Plasmas | Article by Sharmin Sultana and Ioannis (Yannis) Kourakis https://lnkd.in/grDPrEZN Jahangirnagar University; Khalifa University; MDPI #electrostatic #solitarywave #magnet #plasma #physics #openaccess This article belongs to the Special Issue: A Themed Issue in Honor of Professor Reinhard Schlickeiser on the Occasion of His 70th Birthday https://lnkd.in/dQKR_Seb #Abstract The propagation of dissipative electrostatic (ion-acoustic) solitary waves in a magnetized plasma with trapped electrons is considered via the Schamel formalism. The direction of propagation is assumed to be arbitrary, i.e., oblique with respect to the magnetic field, for generality. A non-Maxwellian (nonthermal) two-component plasma is considered, consisting of an inertial ion fluid, assumed to be cold for simplicity, and electrons. A (kappa) 𝜅 -type distribution is adopted for the electron population, in addition to particle trapping taken into account in phase space. A damped version of the Schamel-type equation is derived for the electrostatic potential, and its analytical solution, representing a damped solitary wave, is used to examine the nonlinear features of dissipative ion-acoustic solitary waves in the presence of trapped electrons. The influence of relevant plasma configuration parameters, namely the percentage of trapped electrons, the electron superthermality (spectral) index, and the direction of propagation on the solitary wave characteristics is investigated.

Path Integral Estimates of the Quantum Fluctuations of the Relative Soliton-Soliton Velocity in a Gross-Pitaevskii Breather | Article by Sumita Datta, Vanja Dunjko and Maxim Olshanii https://lnkd.in/giS6kaxb Alliance University; UMass Boston; MDPI; #nuclei #nuclear #Coulomb #shell #physics #OpenAccess #Abstract In this paper, the quantum fluctuations of the relative velocity of constituent solitons in a Gross-Pitaevskii breather are studied. The breather is confined in a weak harmonic trap. These fluctuations are monitored, indirectly, using a two-body correlation function measured at a quarter of the harmonic period after the breather creation. The results of an ab initio quantum Monte Carlo calculation, based on the Feynman-Kac path integration method, are compared with the analytical predictions using the recently suggested approach within the Bogoliubov approximation, and a good agreement is obtained.

A Review on Scene Prediction for Automated Driving | Review by Anne Stockem Novo, Martin Krüger, Marco Stolpe and Torsten Bertram https://lnkd.in/g7Eycdwr Hochschule Ruhr West; ZF Automotive Safety Germany GmbH; TU Dortmund University; ZF Automotive Safety Germany GmbH; MDPI #automated #driving; #datadriven #modeling; #deeplearning; #scene #prediction; #trajectory #prediction #physics This article belongs to the Special Issue: A Themed Issue in Honor of Professor Reinhard Schlickeiser on the Occasion of His 70th Birthday https://lnkd.in/dQKR_Seb #Abstract Towards the aim of mastering level 5, a fully automated vehicle needs to be equipped with sensors for a 360∘ surround perception of the environment. In addition to this, it is required to anticipate plausible evolutions of the traffic scene such that it is possible to act in time, not just to react in case of emergencies. This way, a safe and smooth driving experience can be guaranteed. The complex spatio-temporal dependencies and high dynamics are some of the biggest challenges for scene prediction. The subtile indications of other drivers’ intentions, which are often intuitively clear to the human driver, require data-driven models such as deep learning techniques. When dealing with uncertainties and making decisions based on noisy or sparse data, deep learning models also show a very robust performance. In this survey, a detailed overview of scene prediction models is presented with a historical approach. A quantitative comparison of the model results reveals the dominance of deep learning methods in current state-of-the-art research in this area, leading to a competition on the cm scale. Moreover, it also shows the problem of inter-model comparison, as many publications do not use standardized test sets. However, it is questionable if such improvements on the cm scale are actually necessary. More effort should be spent in trying to understand varying model performances, identifying if the difference is in the datasets (many simple situations versus many corner cases) or actually an issue of the model itself.

The Birth of the Universe as a Result of the Change of the Metric Signature | Article by Tatyana Shestakova https://lnkd.in/gWAR5Fpv Southern Federal University (former Rostov State University); MDPI #Universe #quantum #physics #OpenAccess This article belongs to the Special Issue Light on Dark Worlds—A Themed Issue in Honor of Professor Maxim Yu. Khlopov on the Occasion of His 70th Birthday https://lnkd.in/df4wJb9T #Abstract In this paper, I discuss the idea that the birth of our Universe may be a result of a quantum transition from a physical continuum with the Euclidean signature to a Lorentzian spacetime. A similar idea was expressed by Andrei D. Sakharov At the classical level, the idea was studied by George F. R. Ellis and his collaborators, who explored if solutions to the classical Einstein equation exist which admit a change of metric signature. The present paper aims at examining possible realizations of this idea at the level of quantum gravity, in the framework of the Wheeler–DeWitt theory and in the extended phase space approach to quantization of gravity. I intend to answer the questions: to answer the questions: Does the Hartle–Hawking wave function imply such a realization? How can this idea be realized in the extended phase space approach to quantum gravity, where the change of signature is described by imposing special conditions on g00-component of the metric in different regions of the physical continuum? The conclusion is that the idea can be realized from a formal mathematical point of view, but it can hardly help in understanding how spacetime structure and time itself appeared from a timeless continuum.

Determining Pitch-Angle Diffusion Coefficients for Electrons in Whistler Turbulence | Article by Felix Spanier, Cedric Schreiner and Reinhard Schlickeiser https://lnkd.in/gGNi3wxs Heidelberg University; North-West University / Noordwes-Universiteit; Max-Planck Institute for Solar System Research; Ruhr-Universit��t Bochum; Kiel University; MDPI #Electron #Turbulence #plasmawave #OpenAccess #physics This article belongs to the Special Issue A Themed Issue in Honor of Professor Reinhard Schlickeiser on the Occasion of His 70th Birthday https://lnkd.in/dQKR_Seb #Abstract Transport of energetic electrons in the heliosphere is governed by resonant interaction with plasma waves, for electrons with sub-GeV kinetic energies specifically with dispersive modes in the whistler regime. In this paper, particle-in-cell simulations of kinetic turbulence with test-particle electrons are performed. The pitch-angle diffusion coefficients of these test particles are analyzed and compared to an analytical model for left-handed and right-handed polarized wave modes.

⭐ Editor’s Choice Article ⭐ Casimir Effect Invalidates the Drude Model for Transverse Electric Evanescent Waves | Article by Galina L. Klimchitskaya and Vladimir M. Mostepanenko https://lnkd.in/ggwEkGNC Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences;Peter the Great St.Petersburg Polytechnic University;Kazan Federal University MDPI (This article belongs to the Special Issue 75 Years of the Casimir Effect: Advances and Prospects) https://lnkd.in/gmnPP8Bd #Casimir #Force #physics The paper brought us to the most plausible resolution of the outstanding problem which troubled the physical community for the last 25 years and was called "The Casimir puzzle." The essence of the problem is that precise measurements of the Casimir force exclude the predictions of the fundamental theory if the relaxation properties of conduction electrons commonly described by the Drude model are taken into account. Surprisingly, if the relaxation properties are disregarded in calculations, the measurement data agree with theoretical predictions. But in actual fact the relaxation properties do exist! In their paper, Profs. Klimchitskaya and Mostepanenko demonstrated that the roots of the long-standing disagreement between experiment and theory are not in an account of relaxation. They have shown that the theoretical results obtained using the Drude model for the usual ("on the mass-shell") electromagnetic waves and also for the virtual ("off the mass-shell") waves possessing the transverse magnetic polarization are almost the same as with the relaxation properties disregarded due to an accidental cancellation. The reason for disagreement turned our to be in only the contribution of the off the mass-shell waves with the trasverse electric polarization. For the waves of this kind, however, the Drude model has no sufficient experimental confirmation. The authors proposed an experiment which should clearly demonstrate the failure of the Drude model for the virtual waves with the trasnverse electric polarization. This experiment is currently in preparation in the laboratory of Prof. Umar Mohideen (the University of California, Riverside).