Hasil untuk "Physics"

A. Bassi, K. Lochan, Seema Satin et al.

We describe the state of the art in preparing, manipulating and detecting coherent molecular matter. We focus on experimental methods for handling the quantum motion of compound systems from diatomic molecules to clusters or biomolecules. Molecular quantum optics offers many challenges and innovative prospects: already the combination of two atoms into one molecule takes several well-established methods from atomic physics, such as for instance laser cooling, to their limits. The enormous internal complexity that arises when hundreds or thousands of atoms are bound in a single organic molecule, cluster or nanocrystal provides a richness that can only be tackled by combining methods from atomic physics, chemistry, cluster physics, nanotechnology and the life sciences. We review various molecular beam sources and their suitability for matter-wave experiments. We discuss numerous molecular detection schemes and give an overview over diffraction and interference experiments that have already been performed with molecules or clusters. Applications of de Broglie studies with composite systems range from fundamental tests of physics up to quantum-enhanced metrology in physical chemistry, biophysics and the surface sciences. Nanoparticle quantum optics is a growing field, which will intrigue researchers still for many years to come. This review can, therefore, only be a snapshot of a very dynamical process.

J. Willard, X. Jia, Shaoming Xu et al.

There is a growing consensus that solutions to complex science and engineering problems require novel methodologies that are able to integrate traditional physics-based modeling approaches with state-of-the-art machine learning (ML) techniques. This article provides a structured overview of such techniques. Application-centric objective areas for which these approaches have been applied are summarized, and then classes of methodologies used to construct physics-guided ML models and hybrid physics-ML frameworks are described. We then provide a taxonomy of these existing techniques, which uncovers knowledge gaps and potential crossovers of methods between disciplines that can serve as ideas for future research.

X. Wen

The subject of this Colloquium is related to the topic of the 2016 Physics Nobel Prize that was awarded to David J. Thouless, F. Duncan M. Haldane, and J. Michael Kosterlitz ``for theoretical discoveries of topological phase transitions and topological phases of matter.'' The Colloquium provides a pedagogical introduction to topological phases of matter from comprehensive point of view of many-body entanglement which is important in quantum physics.

K. Deng, Guoliang Wan, P. Deng et al.

Observations of topological surface states provide strong evidence that MoTe2 is a type-II Weyl semimetal, hosting Weyl fermions that have no counterpart in high-energy physics. Weyl semimetal is a new quantum state of matter1,2,3,4,5,6,7,8,9,10,11,12 hosting the condensed matter physics counterpart of the relativistic Weyl fermions13 originally introduced in high-energy physics. The Weyl semimetal phase realized in the TaAs class of materials features multiple Fermi arcs arising from topological surface states10,11,14,15,16 and exhibits novel quantum phenomena, such as a chiral anomaly-induced negative magnetoresistance17,18,19 and possibly emergent supersymmetry20. Recently it was proposed theoretically that a new type (type-II) of Weyl fermion21,22 that arises due to the breaking of Lorentz invariance, which does not have a counterpart in high-energy physics, can emerge as topologically protected touching between electron and hole pockets. Here, we report direct experimental evidence of topological Fermi arcs in the predicted type-II Weyl semimetal MoTe2 (refs 23,24,25). The topological surface states are confirmed by directly observing the surface states using bulk- and surface-sensitive angle-resolved photoemission spectroscopy, and the quasi-particle interference pattern between the putative topological Fermi arcs in scanning tunnelling microscopy. By establishing MoTe2 as an experimental realization of a type-II Weyl semimetal, our work opens up opportunities for probing the physical properties of this exciting new state.

M. Chi, R. Glaser, Ernest Rees

R. Kingston

Jon Mathews, R. L. Walker

H. Temperley, J. Rowlinson, G. S. Rushbrooke

Asalkhon Alimova, Farruh Atamurotov, Ahmadjon Abdujabbarov et al.

Abstract The motion of spinning particles around a quantum-corrected black hole is examined in this paper. We investigate the dynamics of spinning test particles by using the Mathisson–Papapetrou–Dixon equations, the Tulczyjew spin-supplementary condition, and restricting the motion to the equatorial plane. We determine the innermost stable circular orbit (ISCO), effective potential, and effective force and examine how these depend on the black hole’s $$\alpha $$ α parameter and the particle’s s spin. However, we also take into account a superluminal bound on the motion of the spinning particle since its kinematical four-velocity and dynamical four-momentum are not always parallel. We also show how the parameter $$\alpha $$ α affects the maximum value of the spin parameter s. We determine the critical angular momentum of the particle for which a collision is possible by investigating collisions of spinning particles close to the horizon of a black hole. Finally, we compute the particle’s center-of-mass energy $$\mathcal {E}_{cm}$$ E cm and analyze how the spin of the colliding particles affects it.

Peter Athron, Csaba Balázs, Jon Butterworth et al.

In this work, we review the history and current role of global fits in the search for physics beyond the Standard Model~(BSM), including precision tests of the Standard Model (SM). Although BSM global fits were initially focused on minimal supersymmetric models, we describe how fits have evolved in response to new data from the Large Hadron Collider (LHC) and elsewhere, expanding to encompass a broad spectrum of BSM scenarios including non-minimal supersymmetry, axion-like particles, extended Higgs sectors, dark matter models, and effective field theories such as SMEFT. We discuss how the role of global fits has shifted from forecasting possible signals of new physics at the LHC to understanding the impact of null results from LHC run-I and II and the discovery of the Higgs boson, and how interest has shifted from global fits for parameter estimation to comprehensive model comparison. We close by discussing potential trends and future applications, emphasizing the potential for machine learning and artificial intelligence to enhance the efficiency of sampling algorithms and comparison between theory and experiment, as well as collaboration and software development.

Ali Övgün, Reggie C. Pantig, Bobomurat Ahmedov et al.

Motivated by the work of Scully \textit{et al.} [ \textcolor{blue}{Proc. Nat. Acad. Sci. 115, 8131 (2018)}] and Camblong \textit{et al.}[ \textcolor{blue}{Phys. Rev. D 102, 085010 (2020)}], we investigate horizon-brightened acceleration radiation (HBAR) for freely falling two-level atoms in the geometry of a Bardeen regular black hole. Building on the quantum-optics approach to acceleration radiation and its near-horizon conformal quantum mechanics (CQM) structure, we show that the dominant physics is again governed by an inverse-square potential in the radial Klein-Gordon equation, with an effective coupling fixed by the Bardeen surface gravity. Using geodesic expansions and a near-horizon CQM reduction of the scalar field, we derive the excitation probability for atoms falling through a Boulware-like vacuum in the presence of a stretched-horizon mirror. The resulting spectrum is Planckian in the mode frequency, with a temperature determined by the Bardeen Hawking temperature. We analyze how the regular core parameter controls the strength of the radiation and demonstrate that the excitation probability is strongly suppressed as the geometry approaches the extremal (cold remnant) limit. Numerical results illustrate the dependence of the spectrum on the Bardeen parameter and on the atomic transition frequency.

Haiyang Liu, Zhe Li, Zeqiu Hu et al.

All optical soliton communication is a new generation of ultra-long distance and ultra-high speed optical fiber communication technology. Optical cavity solitons (CSs), whose pulse property is unique, have shown great potentials in optical soliton communication systems. Here, a theoretical model of nonlinear fiber resonator for CS generation is proposed. The effect of pump laser and resonant cavity parameters on the CS pulse performance is detailedly investigated and deeply analysed. Furthermore, the synergistic effect of continuous wave (CW) pump laser power and pump pulse peak power, and the synergistic effect of dispersion condition, fiber nonlinear coefficient and fiber length on the generation and property of CS pulse are respectively discussed and summarized. Finally, the launch conditions and parameter variation tolerances of cavity soliton in nonlinear fiber resonant cavity have been successfully generalized. These results can provide important instruction to the experimental generation and optimization of CS pulse.

P. Tannenwald, P. Kelley, B. Lax

Yizhou Dai, Huan Li, Chuanhao Wang et al.

Abstract Electrochemical CO2 conversion to methane, powered by intermittent renewable electricity, provides an entrancing opportunity to both store renewable electric energy and utilize emitted CO2. Copper-based single atom catalysts are promising candidates to restrain C-C coupling, suggesting feasibility in further protonation of CO* to CHO* for methane production. In theoretical studies herein, we find that introducing boron atoms into the first coordination layer of Cu-N4 motif facilitates the binding of CO* and CHO* intermediates, which favors the generation of methane. Accordingly, we employ a co-doping strategy to fabricate B-doped Cu-N x atomic configuration (Cu-N x B y ), where Cu-N2B2 is resolved to be the dominant site. Compared with Cu-N4 motifs, as-synthesized B-doped Cu-N x structure exhibits a superior performance towards methane production, showing a peak methane Faradaic efficiency of 73% at −1.46 V vs. RHE and a maximum methane partial current density of −462 mA cm−2 at −1.94 V vs. RHE. Extensional calculations utilizing two-dimensional reaction phase diagram analysis together with barrier calculation help to gain more insights into the reaction mechanism of Cu-N2B2 coordination structure.

Varignier Geoffrey, Fondement Valentin, Carasco Cédric et al.

MCNP and GEANT4 are two reference Monte Carlo nuclear simulators, MCNP being the standard in the Oil & Gas nuclear logging industry. While performing a simulation benchmark of these two software for the purpose of “Cased Hole” wellbore evaluation, discrepancies between MCNP and GEANT4 were observed: computational experiments were performed first in a theoretical and simplified environment using spherical models, then in a more realistic “Open Hole” wellbore context with simplified logging tools. Results of this comparison show an excellent overall agreement for gamma-gamma physics and an acceptable agreement for neutron-neutron physics. However, the agreement for neutron-gamma physics is satisfactory only for certain lithologies and energy windows, but not acceptable for other operating conditions. These results need to be put in perspective with the current use of nuclear simulation in the logging industry. Indeed, wellbore evaluations rely on charts simulated with Monte Carlo codes in various contexts. In the case of radially heterogeneous environments such as “Cased Hole” wellbores, nuclear simulations are mandatory to precisely determine the radial sensitivity of logging tools via the so-called sensitivity functions. The feasibility of wellbore inversion relies on the physical validity of such sensitivity functions obtained from nuclear simulations. This MCNP vs. GEANT4 benchmark was conducted with the perspective to secure the physical fundamentals used for building the sensitivity functions of logging tools.

Nobuharu Nakajima

The physical interpretation of weak measurements has been the subject of much debate. It is known that anomalous phenomena and results that appear in weak measurements are essentially related to the phase of the quantum system being measured. Consideration of the phase is important to clarify its physical interpretation. In classical wave optics, there has long been studies on methods of measuring or retrieving the phase of a wave function. We here present that one of those methods, the analytic phase retrieval based on the properties of entire functions, has a close connection with weak measurements in quantum physics. We explain such a connection for two emblematic optical weak-measurements that have the same mathematical formalism as quantum systems: one is a system for weak measurements of polarized light displacement in a birefringent crystal, and the other is a system for the direct measurement of a wave function by weakly coupling it to a pointer. In those two systems, we show that the pre- and post-selection of polarized light provides a filtering effect similar to that utilized in the analytic phase retrieval.

Xiongye Zhang, Lixin Zhang, Xue Hu et al.

The rotary tillage knife roller, as one of the typical soil-touching parts of the tillage equipment cutting process, is in direct contact with the soil. During the cutting process, there are problems related to structural bending, deformation, and high power consumption, caused by impact and load, and it is difficult to observe the micro-change law of the rotary tillage tool and soil. In view of the above problems, we took the soil of the cotton experimental field in Shihezi, Xinjiang, and the soil-contacting parts of the rotary tillage equipment, specifically the rotary tiller roller, as the research subject. Using the finite-element method (FEM) to simulate the structure of the rotary tiller with different bending angle parameters, we obtained its average stress and deformation position information, and obtained a range linear relationship between the bending angle and the structural performance of the rotary tiller tool. Using discrete element method (DEM)-based simulation to build the corresponding contact model, soil particle model, and soil–rotary tillage knife roll interaction model to simulate the dynamic process of a rotary tillage knife roll cutting soil, we obtained the change rules of the soil deformation area, cutting process energy, cutting resistance, and soil particle movement. By using the orthogonal simulation test and the response surface method, we optimized the kinematic parameters of the rotary tiller roller and the key design parameters of a single rotary tiller. Taking the reduction of cutting power consumption as the optimization goal and considering the influence of the bending angle on its structural performance, the optimal parameter combination was obtained as follows: the forward speed was 900 m/h, the rotation speed was 100 rad/min, the bending angle was 115°, and the minimum power consumption of the cutter roller was 0.181 kW. The corresponding average stress and deformation were 0.983 mm and 41.826 MPa, which were 15.8%, 13%, and 7.9% lower than the simulation results of power consumption, stress, and deformation under the initial parameter setting, respectively. Finally, the effectiveness of the simulation optimization model in reducing power consumption and the accuracy of the soil-cutting simulation were verified by a rotary tilling inter-field test, which provided theoretical reference and technical support for the design and optimization of other typical soil-touching parts of tillage and related equipment, such as disc harrow, ploughshare, and sub-soiling shovel.

Naotaka Yoshikawa, Kazuma Ogawa, Yoshua Hirai et al.

Weyl semimetals exhibit a unique feature known as Weyl nodes, which give rise to non-trivial topological features such as an anomalous Hall effect, and there are many efforts to try and control such properties. Here, the authors report light-induced chirality switching in a ferromagnetic Weyl semimetal Co3Sn2S2 using circularly polarized mid-infrared light pulse excitation.

Christian W. Bauer, Zohreh Davoudi, A. Baha Balantekin et al.

It is for the first time that Quantum Simulation for High Energy Physics (HEP) is studied in the U.S. decadal particle-physics community planning, and in fact until recently, this was not considered a mainstream topic in the community. This fact speaks of a remarkable rate of growth of this subfield over the past few years, stimulated by the impressive advancements in Quantum Information Sciences (QIS) and associated technologies over the past decade, and the significant investment in this area by the government and private sectors in the U.S. and other countries. High-energy physicists have quickly identified problems of importance to our understanding of nature at the most fundamental level, from tiniest distances to cosmological extents, that are intractable with classical computers but may benefit from quantum advantage. They have initiated, and continue to carry out, a vigorous program in theory, algorithm, and hardware co-design for simulations of relevance to the HEP mission. This community whitepaper is an attempt to bring this exciting and yet challenging area of research to the spotlight, and to elaborate on what the promises, requirements, challenges, and potential solutions are over the next decade and beyond.

Antonio Vassallo, Pedro Naranjo, Tim Koslowski

The goal of this essay is twofold. First, it provides a quick look at the foundations of modern relational mechanics by tracing its development from Julian Barbour and Bruno Bertotti's original ideas until present-day's pure shape dynamics. Secondly, it discusses the most appropriate metaphysics for pure shape dynamics, showing that relationalism is more of a nuanced thesis rather than an elusive one. The chapter ends with a brief assessment of the prospects of pure shape dynamics in light of quantum physics.