arXiv Physics @arxiv_physics@qoto.org

Digital innovation in education has revolutionized teaching and learning processes, demanding a rethink of pedagogical competence among educators. This study evaluates the preparation of instructors to use digital technologies into their educational practices. The study used a mixed-methods approach, integrating both qualitative interviews and quantitative surveys to evaluate teachers' institutional support systems, beliefs, and technical proficiency. The results show that even while a large number of educators acknowledge the benefits of digital tools, problems including poor professional development and change aversion still exist. In order to improve digital pedagogical preparation, the study emphasizes the necessity of focused training initiatives and encouraging institutional regulations. There is discussion on the implications for educational institutions and policymakers.

The development of simple, scalable, and cost-effective methods to prepare Van der Waals materials for thermoelectric applications is a timely research field, whose potential and possibilities are still largely unexplored. In this work, we present a systematic study of ink-jet printing and drop-casting deposition of 2H-phase SnSe2 and WSe2 nanoflake assemblies, obtained by liquid phase exfoliation, and their characterization in terms of electronic and thermoelectric properties. The choice of optimal annealing temperature and time is crucial for preserving phase purity and stoichiometry and for removing dry residues of ink solvents at inter-flake boundaries, while maximizing the sintering of nanoflakes. An additional pressing is beneficial to improve nanoflake orientation and packing, thus enhancing electric conductivity. In nanoflake assemblies deposited by drop casting and pressed at 1 GPa, we obtained thermoelectric power factors at room temperature up to 2.2x10^-4 mW m^-1 K^-2 for SnSe2 and up to 3.0x10^-4 mW m^-1 K^-2 for WSe2.

In the paper it is reported that Bell's correlation formula allows an Einstein local hidden variables explanation. The key is the application of Petis integration.

In a recent paper by Umrigar and Anderson, the authors make an important statement: it is possible to misunderstand the behavior of physical objects (parts of a spacecraft) if that object has reached a velocity comparable to the speed of light. Achieving such a velocity for a spacecraft is critical for interstellar travel, since only traveling at such speeds makes travel to distant stars possible within a human lifetime. Last years, several ideas have been proposed to achieve relativistic velocities for a spacecraft. The authors of these ideas understand that this task is very difficult due to technological obstacles. However, when describing these projects, the authors omit mentioning possible obstacles of physical origin. The paper by Umrigar and Anderson is the first to consider physical limitations on construction of future spacecraft. In this Comment, it will be shown that, according to Umrigar and Anderson, not only technological obstacles will arise in the project of interstellar flights, but also the physical limitations of a spacecraft moving at relativistic velocities may become more serious problems for the implementation of such a project.

The present paper reanalyzes the problem of the refractive properties of the physical vacuum and their modification under the action of the gravitational field and the electromagnetic field. This problem was studied in our previous works and in the subsequent works of the researchers: Leuchs, Urban, Mainland and their collaborators. By modeling the physical vacuum as a particle-antiparticle system, we can deduce with a certain approximation, in a semiclassical theory, the properties of the free vacuum and the vacuum modified by the interaction with a gravitational field and an electromagnetic field. More precise calculation of permittivities of free vacuum and near a particle can lead to a non-point model of the particle. This modeling can follow both the quantum and the general relativistic path as well as the phenomenological path, the results complementing each other.

Current average horizontal beta beat measurements between operating Interaction Regions (IR) in the Relativistic Heavy Ion Collider (RHIC) are around 15 percent along with significant variation in s star. This threshold to measure the linear optics can be improved by considering preprocessing methods involving data reconstruction such as Dynamic Mode Decomposition (DMD), and cross checking between different method variations, model independent and dependent methods, and turn by turn (TBT) datasets. These were then applied to analyze the movement of horizontal s star at the 8 o clock IR at RHIC (IR8). This movement was done using an optics response matrix to determine magnet strengths necessary to move horizontal s star without disturbing other optics. Data preprocessing was found to significantly aid in beat reduction around IP, with DMD demonstrating the least variability between preprocessing methods and between horizontal s star movements. These preprocessing methods will be implemented into RHIC for future linear optics analysis.

Coulomb blockade thermometers (CBTs) are versatile and, in principle, primary thermometers operating down to the micro-Kelvin range but bias heating spoils the thermometry and the primary mode. Here, we introduce a method to extract the CBT electron temperature in the presence of heat created by an arbitrary bias voltage, and without assumptions on the heat flow mechanisms. The charging energy is extracted with high precision and without any other knowledge, thus making true primary thermometry possible. The experiment also reveals a subtle dependence of the charging energy on phonon temperature below 100 mK likely due to the amorphous AlO$_x$ tunnel junctions.

An experimental continuous-wave (cw) pump-probe scheme is demonstrated by investigating the population and photoionization dynamics of an atomic system. Specifically, $^6$Li atoms are initially prepared in optically pumped $2^{2}S_{1/2}$ and $2^{2}P_{3/2}$ states before being excited via multi-photon absorption from a tunable femtosecond laser. The subsequent cascade back to the ground state is analyzed by ionizing the atoms in the field of a cw optical dipole trap laser. Conventional spectroscopic methods such as standard cold-target recoil-ion momentum spectroscopy (COLTRIMS) or velocity map imaging (VMI) cannot provide simultaneous momentum and time-resolved information on an event-by-event basis for the system investigated here. The new approach overcomes this limitation by leveraging electron-recoil ion coincidences, momentum conservation, and the cyclotron motion of the photoelectron in the magnetic spectrometer field. This enables the reconstruction of ionization times and time-of-flight of the charged target fragments with nanosecond resolution. As a result, not only can three-dimensional photoelectron momentum vectors be determined, but the (incoherent) population dynamics of the atomic system also become accessible. Future applications exploring coherent atomic dynamics on the nanosecond timescale would not only expand the scope of time-resolved spectroscopy but can also aid in developing coherent control schemes for precise atomic manipulation.

Microbial motion is typically analyzed by simplified models in which trajectories exhibit straight runs (perhaps with added Gaussian noise) followed by random, discrete tumbling events. We present the results of a statistical analysis of the angular dynamics for four different swimming microbes: tumbling and smooth-swimming strains of \textit{Bacillus subtilis} and two Eukaryotic algae, \textit{Tetraselmis suecica} and \textit{Euglena gracilis}. We show that the angular statistics closely resemble a Voigt profile, the convolution of a Gaussian (Lévy index $α=2$) and Lorentzian (Lévy index $α=1$) distribution. This distribution is ubiquitous for all four microbes. Rather than modeling tumbling as a discrete process, we model tumbling dynamics as a continuous process: Lévy flights in the orientational dynamics using a Lorentzian noise model. This model is analytically solvable. Each individual microbe trajectory has both stochastic behavior (noise) and varying deterministic behavior, such as helices of different sizes and frequencies and circular arcs with different radii. We model the distribution of different deterministic behavior via an ensemble theory. The deterministic behavior (e.g., circular arcs) comes from physical observations of the swimming behavior and explains many of the qualitative features in the data that cannot be explained by a pure noise model. From this theory, we estimate the strength of Lorentzian noise, the physical rotational diffusion constant, and some relevant parameters relating to the distributions of deterministic behavior. This analysis shows that in some cases Gaussian noise is not the dominant process responsible for the angular statistics following a Voigt profile.

A fast and highly efficient frequency modulation at a high power level is described. The system incorporates ferroelectric phase shifters and a magic-T or a circulator. A magnetron may be considered as a potential application. The magnetron output may be converted to a selected reference frequency with negligible insertion loss. The method also allows simultaneous amplitude and phase control.

We present a matter-space framework characterizing particles and establish its compatibility with electromagnetism. In this approach, matter, such as photons, is considered to reside in a three-dimensional matter space, with the electromagnetic fields observed in four-dimensional spacetime interpreted as projections from this space. By imposing gauge symmetry through constraint equations, we derive the relationship between the vector field $A_a$ and the antisymmetric tensor $F_{ab}$, forming part of Maxwell's equations. The remaining Maxwell equation is obtained through the action principle in relativistic fluid dynamics. Notably, we demonstrate that this imposition of the gauge symmetry and constraints develop the dynamics. This framework offers a fresh perspective on particle-field interactions and deepens the theoretical foundation of relativistic fluid dynamics.

Mazur and Mottola's gravastar model represents one of the few serious alternatives to the traditional understanding of the black hole. The gravastar is typically regarded as a theoretical alternative for the black hole. This article investiagtes the creation of gravastar(gravitational vacuum star) within the realm of cylindrically symmetric space-time utilizing the Kuchowicz metric potential. A stable gravastar comprises of three distinct regions, starting with an interior region marked by positive energy density and negative pressure $(p=-ρ)$ which is followed by an intermediate thin shell, where the interior negative pressure induces a outward repulsive force at each point on the shell. Ultra-relativistic stiff fluid makes up the thin shell governed by the equation of state(EoS) $(p=ρ)$, which meets the Zel'dovich criteria. And then comes the region exterior to it which is total vacuum. In this scenario, the central singularity is eliminated and the event horizon is effectively substituted by the thin bounding shell. Employing the Kuchowicz metric potential we have derived the remaining metric functions for the interior region and the shell regions yielding a non-singular solution for both the regions. Additionally, we have investigated various characteristics of this shell region including its proper shell length, the energy content and entropy. This theoretical model successfully resolves the singularity issue inherent to the black holes. Therefore, this gravastar model presents a viable alternative to the traditional black holes, reconciled within the context of Einstein's theory of General Relativity.

The potential intensity (PI) theory of tropical cyclones (TCs) provides a reasonable estimate of the maximum intensity of a steady-state TC in a quiescent environment. The traditional PI theory relies on the symmetric neutrality (SN) assumption, where the isolines of absolute angular momentum (M) are parallel to the saturation entropy (s*) surfaces within the eyewall updraft. When the SN is not valid, there is currently no quantitative theory that explicitly describes how these surfaces directly relate to the maximum tangential wind (vmax) near the surface. In this study, the PI theory is revisited without making the SN assumption. Under non-SN conditions, it is found that the balance between the centrifugal torque and baroclinic torque provides a strong constraint on the vortex structure and balanced intensity. Specifically, it is shown that the gradient between s* and M along constant temperature (T) throughout the saturated eyewall determines the structure of the M surface and the balanced intensity at the low level. The same technique can be applied to obtain the generalized terms that correspond to the unbalanced component. It is shown that this generalized vmax equation is the natural extension of the traditional PI formula into the non-symmetric neutrality regime. Verifying against axisymmetric simulations, it is shown that the generalized vmax equation can accurately quantify the various contributions to vmax during the rapid intensification process. The implications of these findings on the TC rapid intensification, such as the TC inner-core structure and the upper-tropospheric mixing process, are examined.

When should we be satisfied and when should we look for greener pastures? When is the perfect the enemy of the good? This type of question arises in many different contexts, including business, politics, resource exploitation, and our personal lives. Folk intuition suggests that people should aim for above-average results, but overreaching can lead to failure. Here, we mathematically formalize this intuition and relate it to empirical research across diverse domains. We model a search for strategies that have uncertain rewards over a fixed time period. The agent (i.e. searcher) knows the statistical distribution of rewards across strategies. At each time step, the agent either is satisfied and sticks with their current strategy or continues searching. We prove that the agent's optimal satisfaction threshold is both finite and strictly larger than the mean of available rewards. Compared to the optimal threshold, being too ambitious has a higher expected cost than being too cautious, implying that uncertainty over the reward distribution should motivate caution. The optimal satisfaction threshold becomes larger if the search time is longer, or if the reward distribution is rugged (i.e., has low autocorrelation) or left skewed. Using upward social comparison to assess the reward landscape biases agents towards never being satisfied, which decreases their expected performance substantially. We discuss how these insights can be applied empirically, using examples from entrepreneurship, economic policy, political campaigns, online dating, and college admissions.

Normal conducting linear particle accelerators consist of multiple rf stations with accelerating structure cavities. Low-level rf (LLRF) systems are employed to set the phase and amplitude of the field in the accelerating structure, and to compensate the pulse-to-pulse fluctuation of the rf field in the accelerating structures with a feedback loop. The LLRF systems are typically implemented with analogue rf mixers, heterodyne based architectures and discrete data converters. There are multiple rf signals from each of rf station, so the number of rf channels required increases rapidly with multiple rf stations. With many rf channels, the footprint, component cost and system complexity of the LLRF hardware increase significantly. To meet the design goals to be compact and affordable for future accelerators, we have designed the next generation LLRF (NG-LLRF) with higher integration level based on RFSoC technology. The NG-LLRF system samples rf signals directly and performs the rf mixing digitally. The NG-LLRF has been characterized in a loopback mode to evaluate the performance of the system and tested with a standing-wave accelerating structure, a prototype for the Cool Copper Collider (C3) with peak rf power up to 16.45 MW. The loopback test demonstrated amplitude fluctuation below 0.15% and phase fluctuation below 0.15 degree, which are considerably better than the requirements of C3. The rf signals from the different stages of accelerating structure at different power levels are measured by the NG-LLRF, which will be critical references for the control algorithm designs. The NG-LLRF also offers flexibility in waveform modulation, so we have used rf pulses with various modulation schemes which could be useful for controlling some of rf stations in accelerators. In this paper, the high-power test results at different stages of the test setup will be summarized, analyzed and discussed.

This study formulates a volumetric inverse-design methodology to generate a pair of complementary focusing metalenses for terahertz imaging: the two lenses exhibit equal and opposite shifts in focal length with frequency. An asymmetry arises, where we find a focal length that decreases with frequency to be more challenging to achieve (without material dispersion) given fabrication constraints, but it is still possible. We employ topology optimization, coupled with manufacturing constraints, to explore fully freeform designs compatible with 3D printing. Formulating an optimization problem that quantifies the goal of maximal complementary focal shifts, while remaining differentiable and tractable, requires a carefully selected sequence of constraints and approximations.

The inverse diffusion flame (IDF) can experience thermoacoustic instability due to variations in power input or flow conditions. However, the dynamical transitions in IDF that lead to this instability when altering control parameters have not been thoroughly investigated. In this study, we explore the control parameters through two different approaches and employ multifractal detrended fluctuation analysis to characterize the transitions observed prior to the onset of thermoacoustic instability in the inverse diffusion flame. Our findings reveal a loss of multifractality near the region associated with thermoacoustic instability, which suggests a more ordered behavior. We determine that the singularity exponent, the width of the multifractal spectrum, and the Hurst exponent are reliable indicators of thermoacoustic instability and serve as effective classifiers of dynamical states in inverse diffusion flames.

We evaluate the roles general relativistic assumptions play in simulations used in recent observations of black holes including LIGO-Virgo and the Event Horizon Telescope. In both experiments simulations play an ampliative role, enabling the extraction of more information from the data than would be possible otherwise. This comes at a cost of theory-ladenness. We discuss the issue of inferential circularity, which arises in some applications; classify some of the epistemic strategies used to reduce the extent of theory-ladenness; and discuss ways in which these strategies are model independent.

Ionization potential depression (IPD) is of crucial importance to understand and accurately predict the properties of dense partially ionized plasmas. Many models of IPD have been developed that, however, exhibit largely varying results. Recently, a novel approach was proposed that is based on first-principles quantum Monte Carlo simulations and that was demonstrated for hydrogen [Bonitz \textit{et al.}, Phys. Plasmas (2024)]. Here this concept is discussed in more detail. Particular attention is devoted to the Fermi barrier that electrons have to overcome upon ionization and which significantly contributes to IPD when the nuclear charge increases.