Journal of the Korean Physical Society最新文献

We consider the holographic dark energy model with axial torsion which satisfies the cosmological principle. Subsequently, by using the torsional analogs of Friedmann equations for the new equation from Einstein–Cartan gravity theory, we obtain the equation of state for dark energy in this model. We find that the extended holographic dark energy from the particle horizon as the infrared (IR) cut-off does not give the accelerating expansion of the universe. Also, employing the future event horizon as IR cut-off still achieves the accelerating expansion of the universe. In contrast, there is a possibility that the Hubble radius as IR cut-off achieves the accelerating expansion of the universe in superluminal region for axial torsion. More precisely, the current value of ratio for torsion to the matter density, (gamma ^{0}=0.5) gives the equation of state of dark energy (omega _{Lambda }cong -1).

Quantum state tomography (QST) forms the foundational framework in quantum computing, enabling precise characterization of quantum states through specialized measurement arrays. This is crucial for assessing the fidelity and coherence of quantum states in various quantum systems. The complexity and high dimensionality of quantum states require advanced statistical methods to meet modern quantum paradigms’ precision and computational needs, as traditional methods often struggle with inefficiencies and inaccuracies. Conventional approaches in QST typically use linear inversion and maximum likelihood estimators, which often face computational redundancies and perform sub-optimally in high-dimensional quantum architectures. This exposition introduces pioneering statistical methodologies that combine Bayesian Inference, Variational Quantum Eigensolver, and Quantum Neural Networks to achieve enhanced fidelity approximation. The analytical discussion is supported by synthetic quantum states, demonstrating the efficacy and applicability of these statistical methods across various quantum matrices. Preliminary empirical results show a significant increase in fidelity and a notable reduction in error margins, highlighting the potential of these advanced statistical methodologies in optimizing quantum state reconstructions. Additionally, leveraging the inherent symmetry properties in quantum systems could further improve the efficiency and accuracy of state reconstructions, offering additional pathways for advancing the field.

Synaptic transistors are considered to hold great potential as electronic devices for constructing brain-inspired neuromorphic cognitive systems. Synaptic transistors made of degradable and environmentally friendly materials are a common concern among researchers today. Egg whites are rich in sources and contain abundant hydrophilic functional groups, including –NH and –OH groups, which can facilitate the movement of protons. In this paper, a synaptic transistor using egg white as the gate dielectric for biomimetic simulation and neuromorphic computing is prepared. The fabricated synaptic transistor successfully simulates typical biological synaptic behaviors, such as excitatory postsynaptic current and double-pulse facilitation, and effectively models the transition from short-term memory to long-term memory. Furthermore, based on the long-term memory and conductance linearity of egg-white gated synaptic transistors, it completes the neuromorphic computation for handwritten digit recognition in neural networks, indicating that egg-white gated synaptic transistors have great potential for application in “green” neural-form electronic devices.

We investigate an expansion of the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model aiming at realizing spontaneous CP violation. By introducing singlet heavy Majorana neutrinos and an additional new singlet scalar, we formulate the Yukawa Lagrangian and scalar potential for the extended model, highlighting their pivotal role in inducing CP violation. This study reveals that CP can spontaneously be broken at the 1-loop level, facilitated by the generation of the quartic couplings in the scalar potential which are imperative for inducing spontaneous CP violation. We discuss the implications of the model on the new axion. By presenting the leptonic Yukawa Lagrangian and the structure of the Dirac neutrino mass matrix within the minimal seesaw framework, we study the interply between the CP-violating phase arising from the extended DFSZ model and the phases of the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) mixing matrix. A brief numerical analysis is conducted to illustrate the compatibility of the extended DFSZ model with observed neutrino oscillation parameters, providing insights into the origin of leptonic CP violation.

Korea-4GSR, a new synchrotron radiation facility currently under construction in Ochang, Chungbuk, South Korea, introduces three types of in-vacuum undulators (IVUs) for its first phase hard X-ray beamlines: IVU20, IVU22, and IVU24. These IVU types share a common 3-m-long framework capable of adjusting the magnetic gap size between 5 and 18 mm, but they differ in the undulator period length (λ_u). This study characterizes their photon beams in terms of brightness, spectral coverage, source size, angular divergence, coherent fraction, coherent flux, and total and central cone radiation powers, using undulator calculations. The three IVU types are comparable in brightness. IVU20 is the most coherent, although lacking spectral continuity at around 7.5 keV. IVU22 and IVU24 ensure spectral continuity, but their coherent flux is moderately compromised. The performance of the undulators is assessed in comparison to the Pohang Light Source-II (PLS-II) undulator and the U21 undulator at Advanced Photon Source Upgrade (APS-U).

The expansion and decay of excited and compressed nuclear matter produced in heavy-ion collisions across a broad range of incident energies are largely dependent on collective flow. Hydrodynamic theories suggest that the fluid-like behavior of nuclear matter produces a substantial azimuthal correlation in the particle emission. The greatest opportunity to discover nuclear matter compressibility and, indirectly, the nuclear equation of state is through precise measurements of collective flow. The collective flow of projectile fragments (PFs) of charge (Zge 2) produced in (^{84})Kr in interacts with emulsion (composite target) and Ag(Br) target at 1 A GeV for (N_{text {PF}}ge 3) and (N_{alpha }ge 3) has been evaluated using azimuthal correlation functions. The collective flow is observed to be the most pronounced in semi-central collisions. The amplitude of the collective flow appears to be pretty stable at relativistic energy, according to our observation. Additionally, the obtained outcomes are compared to other existing experimental data.

The propagation of microcrack and grain growth in tungsten occurred at condition of transient heat loads was investigated experimentally, observing the effect on macrocrack development induced by stress intensification in time order. The temperature variation in short time, with frequency 30 Hz, heat flux 0.1 GWm⁻², duration 2 ms at base temperature 1150 °C, induces fatigue fracture on the surface of tungsten, resulting in the formation of microcrack. Since the effective spatial temperature variation is limited to a few micron, microcrack is also occurred at the comparable depth. Following the initiation of microcrack, the grain growth propagation depth over time is measured and calculated based on the grain growth model with measuring the associated constants of the model. Within the grain growth layer, the degraded material properties at the microcrack tip lead to stress intensification which ultimately develop into macrocrack with order of millimeters. The study investigates that the subsurface microstructural changes in tungsten, caused by transient heat loads, have the potential to develop into macrocrack that extend into the deeper bulk area.

The RAON accelerator is a facility that can generate and accelerate various kinds of ion beams from proton to uranium for a variety of science programs like nuclear sciences, bio-medical sciences, neutron physics, and so on. For efficient beam acceleration, there are low energy and high energy superconducting accelerator sections with different kinds of superconducting cavities which have different optimum betas and RF frequencies in the RAON accelerator. At the low energy superconducting accelerator section, the installation of the accelerator devices and the initial beam commissioning were successfully completed in 2023. Currently, the development of the superconducting cavities in the high-energy superconducting accelerator section is in progress. Here, we will present the recent simulation results of the beam dynamics for the high energy superconducting accelerator section and describe the correction of the distorted beam orbits induced by machine errors as varying the number and location of steering magnets.

We report a promising strategy to enhance the in-plane thermoelectric (TE) figure of merit (ZT) of few-layer semimetallic PtSe₂ films at 300 K by piling up PtSe₂ layers with the same thickness (3 nm) as stacked PtSe₂/PtSe₂ (3-nm/3-nm) homostructures by a wet-transfer method. We observed that the Seebeck coefficient was enhanced meaningfully upon increasing the number of stacked layers and exceeded ~ 173.2 μV/K with a relatively constant electrical conductivity of ~ 18.4 S/cm at 300 K. By contrast, as the number of layers increased, thermal conductivity also showed a significant reduction, and ultimately, the ZT factor increased by ~ 380% compared to the single-stacked PtSe₂ structure. Such an increase in the ZT factor shows the possibility of a considerable improvement in the TE properties of semimetallic PtSe₂ with a new technique called facile wet-transfer stacking. The proposed method is expected to play a very important role in future microscopic cooling and energy-generating TE device applications.