Hasil untuk "Nuclear and particle physics. Atomic energy. Radioactivity"

Xinran Zeng, Yang Zhang

The electroweak phase transition serves as a crucial portal to explore physics beyond the Standard Model, with profound implications for gravitational waves, baryogenesis, dark matter, and vacuum stability. We review the computational workflow for analyzing cosmological phase transitions, which includes constructing the finite-temperature effective potential, identifying possible phases, tracing transition history, calculating transition rates, milestone temperatures, and thermal parameters, as well as the numerical tools developed for each step. We compare the functionalities, strategies, and applicable scopes of these tools, aiming to provide a practical guide that helps researchers select the most appropriate computational resources for their studies.

Andreas Blommaert, Adam Levine, Thomas G. Mertens et al.

Abstract We compute the double trumpet in sine dilaton gravity via WdW quantization. The wormhole size is discretized. The wormhole amplitude matches the spectral correlation of a finite-cut matrix integral, where matrices have large but finite dimensions. This strongly suggests an identification of the sine dilaton gravity theory with the q-deformed JT gravity matrix integral. At the very least, it captures all universal content of that matrix model. The disk decomposes into the physical (gauge invariant) solutions of the WdW equation, which are trumpets with discrete sizes. This decomposition modifies the usual no-boundary wavefunction to a normalizable one in sine dilaton gravity. We furthermore present an exact quantization of sine dilaton gravity with open and closed end of the world branes. These EOW branes correspond with FZZT branes for the two Liouville theories that make up sine dilaton gravity. The WdW equation implies redundancies in this space of branes, leaving a one parameter family of gauge invariant branes. One gauge choice corresponds with branes discussed by Okuyama in the context of DSSYK. Legendre transforming the EOW brane amplitude reproduces the trumpet. One could read our work as fleshing out the Hilbert space of closed universes in sine dilaton gravity.

David Senjaya, Piyabut Burikham, Tiberiu Harko

Abstract We consider Klein–Gordon equation in the Dyonic Kerr–Sen black hole background, which is the charged rotating axially symmetric solution of the Einstein–Maxwell–Dilaton–Axion theory of gravity. The black hole incorporates electric, magnetic, dilatonic and axionic charges and is constructed in 3+1 dimensional spacetime. We begin our investigations with the construction of the scalar field’s governing equation, i.e., the covariant Klein–Gordon equation. With the help of the ansatz of separation of variables, we successfully separate the polar part, and find the exact solution in terms of Spheroidal Harmonics, while the radial exact solution is obtained in terms of the Confluent Heun function. The quantization of the quasibound state is done by applying the polynomial condition of the Confluent Heun function that gives rise to discrete complex-valued energy levels for massive scalar fields. The real part is the scalar field relativistic quantized energy, while the imaginary part represents the quasibound states’s decay. We present all of the sixteen possible exact energy solutions for both massive and massless scalars. We also present the investigation the Hawking radiation of the Dyonic Kerr–Sen black hole’s apparent horizon, via the Sigurd–Sannan method by making use of the obtained exact scalar wave functions. The radiation distribution function, and the Hawking temperature are also obtained.

Young-Kwon Han, Jeong-Won Seo, Taewon Yuk et al.

Abstract We first point out that the Laia-Tong model realizes the Lieb lattice in the holographic setup. It generates a flat band of sharp particle spectrum together with a Dirac band of unparticle spectrum. We provided an understanding why the Laia-Tong model’s boundary condition generate a flat band and compared it with the mechanism of “compact localized orbits” in the lattice models to provide a physical reason why Lieb and Laia-Tong model should be identified based on the similarity in the flat band generation mechanism. We then construct a model which opens a gap to the Dirac band so that one can realize a well-separated flat band. We then study the phase transition between the gapped and gapless phases analytically. We also made methodological progress to find a few other possible quantizations and we express the Green functions in any quantization in terms of that in the standard quantization. Finally we carried out the problem of back reaction to show that the qualitative feature remains the same.

Camille J. Palmer, Jordan Northrop, Todd S. Palmer et al.

The detailed behavior of neutrons in a rapidly changing time-dependent physical system is a challenging computational physics problem, particularly when using Monte Carlo methods on heterogeneous high-performance computing architectures. A small number of algorithms and code implementations have been shown to be performant for time-independent (fixed source and k-eigenvalue) Monte Carlo, and there are existing simulation tools that successfully solve the time-dependent Monte Carlo problem on smaller computing platforms. To bridge this gap, a time-dependent version of ORNL’s Shift code has been recently developed. Shift’s history-based algorithm on CPUs, and its event-based algorithm on GPUs, have both been observed to scale well to very large numbers of processors, which motivated the extension of this code to solve time-dependent problems. The validation of this new capability requires a comparison with time-dependent neutron experiments. Lawrence Livermore National Laboratory’s (LLNL) pulsed sphere benchmark experiments were simulated in Shift to validate both the time-independent as well as new time-dependent features recently incorporated into Shift. A suite of pulsed-sphere models was simulated using Shift and compared to the available experimental data and simulations with MCNP. Overall results indicate that Shift accurately simulates the pulsed sphere benchmarks, and that the new time-dependent modifications of Shift are working as intended. Validated exascale neutron transport codes are essential for a wide variety of future multiphysics applications.

Masazumi Honda, Ryusuke Jinno, Lucas Pinol et al.

Abstract We make use of Borel resummation to extract the exact time dependence from the divergent series found in the context of stochastic inflation. Correlation functions of self-interacting scalar fields in de Sitter spacetime are known to develop secular IR divergences via loops, and the first terms of the divergent series have been consistently computed both with standard techniques for curved spacetime quantum field theory and within the framework of stochastic inflation. We show that Borel resummation can be used to interpret the divergent series and to correctly infer the time evolution of the correlation functions. In practice, we adopt a method called Borel-Padé resummation where we approximate the Borel transformation by a Padé approximant. We also discuss the singularity structures of Borel transformations and mention possible applications to cosmology.

Shuxuan Ying

Abstract Low energy effective action of bosonic string theory possesses a kind of singular static solution which can be interpreted as a naked singularity. Based on the Hohm–Zwiebach action, the naked singularities could be smoothed out by introducing the complete $$\alpha ^{\prime }$$ α ′ corrections of string theory. In this paper, we present two sets of non-singular solutions, which are also regular everywhere in the Einstein frame. In the perturbative region $$\alpha ^{\prime }\rightarrow 0$$ α ′ → 0 , the solutions reduce to the perturbative results. Our result provides extra evidence for weak cosmic censorship conjecture (WCCC) from a viewpoint of string theory.

Tuan Q. Do, W. F. Kao, Ing-Chen Lin

Abstract Effect of non-canonical scalar fields on the CMB imprints of the anisotropic inflation will be discussed in details in this paper. In particular, we are able to obtain the general formalism of the angular power spectra in the scalar perturbations, tensor perturbations, cross-correlations, and linear polarization in the context of the anisotropic inflation model involving non-canonical scalar fields. Furthermore, some significant numerical spectra will be plotted using the most recent data of Planck as well as the BICEP2 and Keck array. As a result, we find a very interesting point that the TT spectra induced by the tensor perturbations as well as by the linear polarization will increase when the speed of sound decreases.

Andronikos Paliathanasis, Megandhren Govender, Genly Leon

Abstract In this work we present for the first time the general solution of the temporal evolution equation arising from the matching of a conformally flat interior to the Vaidya solution. This problem was first articulated by Banerjee et al. (Phys Rev D 40:670, 1989) in which they provided a particular solution of the temporal equation. This simple exact solution has been widely utilised in modeling dissipative collapse with the most notable result being prediction of the avoidance of the horizon as the collapse proceeds. We study the dynamics of dissipative collapse arising from the general solution obtained via the method of symmetries and of the singularity analysis. We show that the end-state of collapse for our model is significantly different from the widely used linear solution.

Saghar S. Hosseini, Robert Moscrop

Abstract We study the defect groups of D p b $$ {D}_p^b $$ (G) theories using geometric engineering and BPS quivers. In the simple case when b = h ∨(G), we use the BPS quivers of the theory to see that the defect group is compatible with a known Maruyoshi-Song flow. To extend to the case where b ≠ h ∨(G), we use a similar Maruyoshi-Song flow to conjecture that the defect groups of D p b $$ {D}_p^b $$ (G) theories are given by those of G (b)[k] theories. In the cases of G = A n , E 6, E 8 we cross check our result by calculating the BPS quivers of the G (b)[k] theories and looking at the cokernel of their intersection matrix.

Hammoud Sami A., Abbas Mahmoud I.

In this paper, we present a straightforward analytical method for calculating the efficiencies of an ovoid shape (elliptical cylindrical) detector by using a randomly located point source. To determine the activity of an unknown radioactive source, absolute efficiency is required and we should take into account the attenuation of the gamma-ray photons by the source container and the detector housing materials. The soundness of the resultant straightforward analytical method was successfully confirmed by comparison with some published data.

Sandhya Choubey, Monojit Ghosh, Dipyaman Pramanik

Abstract There is a proposal to send a neutrino beam from the Protvino accelerator complex located in Russia to the detector facility called ‘Oscillation Research with Cosmics in the Abyss’ (ORCA) in the Mediterranean sea to study neutrino oscillation. This is called the P2O experiment which will have a baseline of 2588 km. In this paper we carry out an sensitivity study to extract the best possible physics sensitivity of the P2O experiment. In particular, we study the effect of antineutrino runs, the role of background as well as the impact of controlling the systematic uncertainties vis-a-vis the statistics.

K.V. Stepanyantz

Abstract For a general N $$ \mathcal{N} $$ = 1 supersymmetric gauge theory regularized by higher covariant derivatives we prove in all orders that the β-function defined in terms of the bare couplings is given by integrals of double total derivatives with respect to loop momenta. With the help of the technique used for this proof it is possible to construct a method for obtaining these loop integrals, which essentially simplifies the calculations. As an illustration of this method, we find the expression for the three-loop contribution to the β-function containing the Yukawa couplings and compare it with the result of the standard calculations made earlier. Also we briefly discuss, how the structure of the loop integrals for the β-function considered in this paper can be used for the all-loop perturbative derivation of the NSVZ relation in the non-Abelian case.

Kazuhiro Tanaka

Abstract In the QCD energy-momentum tensor T μν , the terms that contribute to physical matrix elements are expressed as the sum of the gauge-invariant quark part and gluon part. Each part undergoes the renormalization due to the interactions among quarks and gluons, although the total tensor T μν is not renormalized thanks to the conservation of energy and momentum. Recently it has been shown that, through the renormalization, each of the quark and gluon parts of T μν receives a definite amount of anomalous trace contribution, such that their sum reproduces the well-known QCD trace anomaly, T μ μ = β / 2 g F μ ν F μ ν + m 1 + γ m ψ ¯ ψ $$ {T}_{\mu}^{\mu }=\left(\beta /2g\right){F}^{\mu \nu }{F}_{\mu \nu }+m\left(1+{\gamma}_m\right)\overline{\psi}\psi $$ , and the corresponding formulas have been derived up to two-loop order. We extend this result to the three-loop order, working out all the relevant three-loop renormalization structure for the quark and gluon energy-momentum tensors in the (modified) minimal subtraction scheme in the dimensional regularization. We apply our three-loop formula of the quark/gluon decomposition of the trace anomaly to calculate the anomaly-induced mass structure of nucleons as well as pions.

V. I. Afanas’ev, S. Bobashev, A. Bykov et al.

Russian Academy of Sciences (RAS), Vadim Vasil'evich Afrosimov, passed away on 25 March 2019. Vadim Vasil'evich's scientific activity was all his life connected to the Ioffe Institute (PTI), where hewas admitted as a laboratory assistant in 1953 after graduating with honors from the Faculty of Physics and Mechanics of the Polytechnic Institute. At the beginning of his scientific pathway, V VAfrosimov carried out research closely connected to solving the important practical task of providing physical data for work on isotope separation by the electromagnetic method. Intense ion beam production required knowledge of cross sections for the interactions between ion beams and gas atoms and molecules, as well as understanding the physics underlying this interaction. On the turn between 1950s and 1960s, the team of researchers led by V V Afrosimov applied in atom collision physics experimental techniques and methods already known at that time in nuclear physics. This changed the character of research radically. Instead of the integral characteristics of collisions, it became possible to examine each of the colliding particles and to determine its physical and dynamical characteristics, which provided the understanding of the atomic particle interaction physics at the quantum-mechanical level. These results brought the team into the ranks of leaders in our country and in the world in studies of the physics of fundamental processes of collisions of electrons, atoms, and ions actively developing in those years. The national school of world-class specialists in atomic collision physics was created at PTI with the active participation of V V Afrosimov. In 1972, a group of scientists, with V V Afrosimov among them, was awarded the Lenin Prize for work on the physics of electronic and atomic collisions. In the 1960s, a problem of measuring the ion temperature in the plasma of the thermonuclear installations then being constructed arose. Fundamental studies on atom ionization in collisions with hydrogen atoms and ions allowed the team of researchers led by Vadim Vasil'evich to develop the methods and equipment for the corpuscular diagnostics of high-temperature plasma, essentially new in world practice. It was based onmeasurements of the energy andmass spectra of hydrogen, deuterium, and tritium atoms freely leaving the plasma. This allowed separate measurement of the energy distribution function of different isotopes of hydrogen ions and the concentration of isotopes of hydrogen and impurity ions in thermonuclear plasma. In the 1960s±1970s, the elaborated methods and equipment were successfully applied in tokamaks at the Kurchatov Institute of Atomic Energy, which furthered a great interest in corpuscular diagnostics from global centers of fusion research. The series of studies with the participation of VVAfrosimov, including the development and application of corpuscular diagnostics, was awarded the 1981 USSR State Prize. At the present time, devices for corpuscular diagnostics designed at the Ioffe Institute are being widely employed at the largest thermonuclear installations in the world. The diagnostics created under the leadership of V V Afrosimov underlay equipment worked out in Russia to control plasma parameters of the International Thermonuclear Reactor ITER being built in Cadarache (France). For many years, Vadim Vasil'evich was head of the Scientific Council of the USSR Academy of Sciences (RAS) for the problem ``Physics of Electronic and Atomic Collisions'', took an active part in the development of international relations, and organized and headed the work of many Russian and international conferences. V VAfrosimov was elected secretary of the commission of the International Union of Pure and Applied Physics Uspekhi Fizicheskikh Nauk 189 (8) 901 ± 902 (2019) DOI: https://doi.org/10.3367/UFNr.2019.07.038605 Translated by M V Tsaplina PERSONALIA PACS number: 01.60.+q

Johannes Bellm, Stefan Gieseke, Simon Plätzer

Abstract We present an algorithm to combine multiple matrix elements at LO and NLO with a parton shower. We build on the unitarized merging paradigm. The inclusion of higher orders and multiplicities reduce the scale uncertainties for observables sensitive to hard emissions, while preserving the features of inclusive quantities. The combination allows further soft and collinear emissions to be predicted by the all-order parton-shower approximation. We inspect the impact of terms that are formally but not parametrically negligible. We present results for a number of collider observables where multiple jets are observed, either on their own or in the presence of additional uncoloured particles. The algorithm is implemented in the event generator Herwig.

Moein Fakhari, Arya Fallahi, Franz X. Kärtner

We present a design methodology for developing ultrasmall electron injectors and accelerators based on cascaded cavities excited by short multicycle THz pulses obtained from laser-driven THz generation schemes. Based on the developed concept for optimal coupling of the THz pulse, a THz electron injector and two accelerating stages are designed. The designed electron gun consists of a four cell cavity operating at 300 GHz and a door-knob waveguide to coaxial coupler. Moreover, special designs are proposed to mitigate the problem of thermal heat flow and induced mechanical stress to achieve a stable device. We demonstrated a gun based on cascaded cavities that is powered by only 1.1 mJ of THz energy in 300 cycles to accelerate electron bunches up to 250 keV. An additional two linac sections can be added with five and four cell cavities both operating at 300 GHz boosting the bunch energy up to 1.2 MeV using a 4-mJ THz pulse.

Joshua Eby, Madelyn Leembruggen, Joseph Leeney et al.

Abstract If QCD axions form a large fraction of the total mass of dark matter, then axion stars could be very abundant in galaxies. As a result, collisions with each other, and with other astrophysical bodies, can occur. We calculate the rate and analyze the consequences of three classes of collisions, those occurring between a dilute axion star and: another dilute axion star, an ordinary star, or a neutron star. In all cases we attempt to quantify the most important astrophysical uncertainties; we also pay particular attention to scenarios in which collisions lead to collapse of otherwise stable axion stars, and possible subsequent decay through number changing interactions. Collisions between two axion stars can occur with a high total rate, but the low relative velocity required for collapse to occur leads to a very low total rate of collapses. On the other hand, collisions between an axion star and an ordinary star have a large rate, Γ⊙ ∼ 3000 collisions/year/galaxy, and for sufficiently heavy axion stars, it is plausible that most or all such collisions lead to collapse. We identify in this case a parameter space which has a stable region and a region in which collision triggers collapse, which depend on the axion number (N ) in the axion star, and a ratio of mass to radius cubed characterizing the ordinary star (M s /R s 3 ). Finally, we revisit the calculation of collision rates between axion stars and neutron stars, improving on previous estimates by taking cylindrical symmetry of the neutron star distribution into account. Collapse and subsequent decay through collision processes, if occurring with a significant rate, can affect dark matter phenomenology and the axion star mass distribution.

Филипп Иванович Высикайло

P. Reinhard, E. Suraud