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

Federica Cuna, Maria Bossa, Fabio Gargano et al.

The application of advanced Artificial Intelligence (AI) techniques in astroparticle experiments represents a major advancement in both data analysis and experimental design. As space missions become increasingly complex, integrating AI tools is essential for optimizing system performance and maximizing scientific return. This study explores the use of Graph Neural Networks (GNNs) within the tracking systems of space-based experiments. A key challenge in track reconstruction is the high level of noise, primarily due to backscattering tracks, which can obscure the identification of primary particle trajectories. We propose a novel GNN-based approach for node-level classification tasks, specifically designed to distinguish primary tracks from backscattered ones within the tracker. In this framework, AI is employed as a powerful tool for pattern recognition, enabling the system to identify meaningful structures within complex tracking data and to discriminate signal from backscattering with higher precision. By addressing these challenges, our work aims to enhance the accuracy and reliability of data interpretation in astroparticle physics through the advanced deep learning techniques.

Hailong Lu, Nong Xiang, Zehua Qian et al.

Lower hybrid wave (LHW) current drive plays a crucial role in sustaining steady-state (SS) discharges on the Experimental Advanced Superconducting Tokamak (EAST). Hotspots frequently form on the wave antenna and guard limiters during SS operations. Although both experimental and theoretical studies suggest that fast electrons could be responsible for these hotspots, the underlying mechanisms of fast electron generation under typical EAST operational parameters and their impact on the hotspots remain unresolved. In this work, particle-in-cell simulations are used to investigate the interactions between LHWs and electrons in front of the antenna, taking into account the realistic incident power spectra and localized field effects. The results show that, due to resonance overlap, fast electrons are produced through resonant interactions between electrons and LHW components with a high parallel refractive index ( N _∥ ). The velocity distribution function in velocity space is found to significantly depend on plasma parameters near the antenna, such as q _95 , electron temperature, and input power. These fast electrons notably enhance the sheath potential on the guard limiters and increase the heat flux to the wall.

F. Boix Pamies, A. Gottberg

ISAC-TRIUMF operates targets under proton irradiation in the high-power regime of 50 kW (100  μA, 500 MeV) to produce radioactive isotope beams using the isotope separation on-line technique. The targets irradiated at ISAC have a total stopping power significantly lower than 500 MeV resulting in a residual high-power proton beam downstream of the target. The coupling of a supplementary target in a downstream position allows for additional scientific output. Irradiation conditions have been analyzed with the fluka code and relevant achievable research within operational limitations explored. Prominently, the study of material degradation under high radiation fields is of increasing interest due to the steady demand for high-performance materials for new-generation nuclear applications and beam-intercepting components at high-power particle accelerator facilities. Successive irradiations at ISAC yield relevant radiation damage of bulk material samples which can then be characterized using already existing facilities at TRIUMF and partner facilities. Additionally, a variety of isotopes produced by transmutation with research applicability can be harvested from these irradiations. With the purpose of unlocking this complementary research at ISAC-TRIUMF, a secondary target, attached to the primary ISAC target system, has been designed and commissioned.

Tatsuo Kobayashi, Hajime Otsuka, Morimitsu Tanimoto

Abstract Phenomenological aspects of non-invertible symmetries, in particular the flavor structure of quarks and leptons, are studied. We start with a ℤ M discrete symmetry and gauge ℤ2 so as to obtain a non-invertible symmetry. We study which Yukawa textures can be derived from the non-invertible symmetries. Various textures can be realized and some of them cannot be realized by a conventional symmetry. For example, the nearest neighbor interaction texture as well as other interesting textures of quarks and leptons are obtained.

Guillermo A. Mena Marugán, Antonio Vicente-Becerril, Jesús Yébana Carrilero

We investigate the implications of different quantization approaches in Loop Quantum Cosmology for the primordial power spectrum of tensor modes. Specifically, we consider the hybrid and dressed metric approaches to derive the effective mass that governs the evolution of the tensor modes. Our study comprehensively examines the two resulting effective masses and how to estimate them in order to obtain approximated analytic solutions to the tensor perturbation equations. Since Loop Quantum Cosmology incorporates preinflationary effects in the dynamics of the perturbations, we do not have at our disposal a standard choice of privileged vacuum, like the Bunch–Davies state in quasi-de Sitter inflation. We then select the vacuum state by a recently proposed criterion which removes unwanted oscillations in the power spectrum and guarantees an asymptotic diagonalization of the Hamiltonian in the ultraviolet. This vacuum is usually called the NO-AHD (from the initials of Non-Oscillating with Asymptotic Hamiltonian Diagonalization) vacuum. Consequently, we compute the power spectrum by using our analytic approximations and by introducing a suitable numerical procedure, adopting in both cases an NO-AHD vacuum. With this information, we compare the different spectra obtained from the hybrid and the dressed metric approaches, as well as from the analytic and numerical procedures. In particular, this proves the remarkable accuracy of our approximations.

Vincent Deledicque

Abstract It has been suggested recently that the apparent accelerated expansion of the universe could be explained by a bias in the SNIa measurements. Such events indeed occur mainly in overdense regions, where matter is located, and whose dynamics can perhaps not been considered as representative of the one of the universe. In this article, we develop a model to investigate in more detail the effect of this bias. This model depends on one single parameter, related to the void fraction of space, and leads to simple analytical relations. We determine in particular the average metric tensor in overdense regions, and deduce that the scale factor and the rate at which proper time progresses in such regions differ significantly from the corresponding values expected on the average space. We then quantitatively deduce how redshift and luminosity distance measurements are affected by the bias, taking into account the perturbation of the metric tensor. Using a value for the void fraction corresponding to the order of magnitude found in the literature, we show that the model is able to predict a distance modulus versus redshift relation being in excellent agreement with the one corresponding to a universe characterized by $$\Omega _{m,0} = 0.3$$ Ω m , 0 = 0.3 and $$\Omega _{\Lambda ,0} = 0.7$$ Ω Λ , 0 = 0.7 .

Yuji Satoh, Yuji Sugawara

Abstract We consider the interactions of strings on T-folds from the world-sheet point of view which are exact in α′. As a concrete example, we take a model where the internal torus at the SO(8) enhancement point is twisted by T-duality (T-folded), and compute the scattering amplitudes of a class of massless strings. The four-point amplitudes involving both twisted and untwisted strings are obtained in a closed form in terms of the hyper- geometric function. By their factorization, the three-point coupling of the twisted and untwisted strings is found to be suppressed by the chiral momenta along the internal torus, and quantized in integer powers of 1/4. The asymptotic forms of the four-point amplitudes in high-energy limits are also obtained. Our results rely only on general properties of the asymmetric orbifold by the T-duality twist and of the Lie algebra lattice from the symmetry enhancement, and thus may be extended qualitatively to more general T-folds.

Alex Davey, Óscar J. C. Dias, Paul Rodgers et al.

Abstract It has been established that Christodoulou’s formulation of Strong Cosmic Censorship (SCC) is violated by Reissner-Nordström-de Sitter black holes, but holds in four-dimensional Kerr-de Sitter black holes. We show that SCC is also respected by equal angular momenta (cohomogeneity-1) Myers-Perry-de Sitter (MP-dS) in odd d ≥ 5 spacetime dimensions. This suggests that the preservation of SCC in rotating backgrounds might be a universal property of Einstein gravity and not limited to the d = 4 Kerr-dS background. As required to discuss SCC in de Sitter spacetimes, we also study important aspects of the scalar field quasinormal mode (QNM) spectra of MP-dS. In particular, we find eigenvalue repulsions similar to those recently observed in the QNM spectra of asymptotically flat Kerr-Newman black holes. For axisymmetric modes (i.e. with azimuthal quantum number m = 0) there are three distinct families of QNM (de Sitter, photon sphere and near-horizon). However, typically, for non-axisymmetric (m ≠ 0) QNMs, we find that the entire spectra can be described by just two families of QNM (since several overtone sections of the photon sphere and near-horizon families merge). For completeness, we also study the full scalar field QNM spectra of higher-dimensional Schwarzschild-de Sitter black holes.

Lucas N Oliveira, Eriberto Nascimento, Patricia de Lara Antonio et al.

Ethylene-vinyl acetate (EVA) is the flexible plastic material commonly used in industries. The EVA samples, in green, white and black colors were irradiated with absorbed doses of 0.01 kGy up to 10.0 kGy using a 60Co Gamma Cell-220 system, and the Fourier Transform Infrared (FTIR) spectrophotometry technique was used for evaluating the samples. This work aimed to investigate EVA samples in measurements with gamma radiation, analyzing the linearity through the Principal Component Regression (PCR) method and its sensitivity. For sensitivity and linearity, the green samples showed the best results, followed by white and black EVA samples. The PCR method inflated gradually the number of principal components, then reducing the residuals between the measured and calculated values, consequently obtaining maximum linearity of 1.000 for all EVA samples. In conclusion, the FTIR was adequate for the acquisition of absorbance spectra, the linearity via PCR and sensitivity showed good results indicating that the EVA detectors can be useful in radiation measurements.

Ryo Suzuki

Abstract We propose a new example of the AdS/CFT correspondence between the system of multiple giant gravitons in AdS 5 × S 5 and the operators with O(N c ) dimensions in N $$ \mathcal{N} $$ = 4 super Yang-Mills. We first extend the mixing of huge operators on the Gauss graph basis in the su 2 $$ \mathfrak{su}(2) $$ sector to all loops of the ’t Hooft coupling, by demanding the commutation of perturbative Hamiltonians in an effective U(p) theory, where p corresponds to the number of giant gravitons. The all-loop dispersion relation remains gapless at any λ, which suggests that harmonic oscillators of the effective U(p) theory should correspond to the classical motion of the D3-brane that is continuously connected to non-maximal giant gravitons.

Alexander Lehmann, Alexander Rothkopf

Abstract We compute the proper real-time interaction potential between a static quark and antiquark in classical lattice gauge theory at finite temperature. Our central result is the determination of the screened real-part of this potential, and we reconfirm the presence of an imaginary part. The real part is intimately related to the back-reaction of the static sources onto the gauge fields, incorporated via Gauss’s law. Differences in the treatment of static sources in quantum and classical lattice gauge theory are discussed.

Iosif Bena, G. Bruno De Luca, Mariana Graña et al.

Abstract We analyze the stability of four-dimensional de Sitter vacua constructed by compactifying massive Type IIA supergravity in the presence of two O8 sources [1]. When embedded in String Theory the first source has a clear interpretation as an O8− plane, but the second one could correspond to either an O8+ plane or to an O8− plane with 16 D8-branes on top. We find that this latter solution has a tachyonic instability, corresponding to the D8 branes moving away from the O8 − plane. We comment on the possible ways of distinguishing between these sources.

Y. N. Filatov, A. M. Kondratenko, M. A. Kondratenko et al.

Abstract Small perturbative fields in a synchrotron influence both the spin and orbital motion of a stored beam. Their effect on the beam polarization consists of two contributions, a direct kick and an effect of the ring lattice due to orbit perturbation. Spin response function is an analytic technique to account for both contributions. We develop such a technique for the spin-transparent synchrotrons where the design spin motion is degenerate. Several perspective applications are illustrated or discussed. In particular, we consider the questions of the influence of lattice imperfections on the spin dynamics and spin manipulation during an experiment. The presented results are of a direct relevance to NICA (JINR), RHIC (BNL), EIC (BNL) and other existing and future colliders when they arranged with polarization control in the spin-transparent mode.

A. Andreev, A. Popolitov, A. Sleptsov et al.

Abstract We study ћ expansion of the KP hierarchy following Takasaki-Takebe [1] considering several examples of matrix model τ-functions with natural genus expansion. Among the examples there are solutions of KP equations of special interest, such as generating function for simple Hurwitz numbers, Hermitian matrix model, Kontsevich model and Brezin-Gross-Witten model. We show that all these models with parameter ћ are τ-functions of the ћ-KP hierarchy and the expansion in ћ for the ћ-KP coincides with the genus expansion for these models. Furthermore, we show a connection of recent papers considering the ћ-formulation of the KP hierarchy [2, 3] with original Takasaki-Takebe approach. We find that in this approach the recovery of enumerative geometric meaning of τ-functions is straightforward and algorithmic.

S. Rahmani, H. Hassanabadi, Jan Kříž

Abstract Nonleptonic and semileptonic decay widths of $${\Lambda _b} \rightarrow {\Lambda _c}$$ Λb→Λc are analyzed within heavy quark limit and Isgur-Wise formalism. A modified QCD Cornell interaction with the additional logarithmic term in the hyperspherical coordinates is considered and the masses of heavy flavour baryons are calculated. The obtained masses are consequently employed to study the rates of $${\Lambda _b} \rightarrow {\Lambda _c}$$ Λb→Λc . The achieved results are motivating.

Prateek Agrawal, Georges Obied

Abstract We revisit the phenomenology of quintessence models in light of the recently refined version of the de Sitter Swampland conjecture, which includes the possibility of unstable de Sitter critical points. We show that models of quintessence can evade previously derived lower bounds on (1 + w), albeit with very finely-tuned initial conditions. In the absence of such tuning or other rolling quintessence fields, a field with mass close to Hubble is required, which has a generic prediction for (1+ w). Slow-roll single field inflation models remain in tension. Other phenomenological constraints arising from the coupling of the quintessence field with the Higgs or the QCD axion are significantly relaxed.

Thomas W. Grimm, Chongchuo Li, Eran Palti

Abstract The Swampland Distance Conjecture proposes that approaching infinite distances in field space an infinite tower of states becomes exponentially light. We study this conjecture for the complex structure moduli space of Calabi-Yau manifolds. In this context, we uncover significant structure within the proposal by showing that there is a rich spectrum of different infinite distance loci that can be classified by certain topological data derived from an associated discrete symmetry. We show how this data also determines the rules for how the different infinite distance loci can intersect and form an infinite distance network. We study the properties of the intersections in detail and, in particular, propose an identification of the infinite tower of states near such intersections in terms of what we term charge orbits. These orbits have the property that they are not completely local, but depend on data within a finite patch around the intersection, thereby forming an initial step towards understanding global aspects of the distance conjecture in field spaces. Our results follow from a deep mathematical structure captured by the so-called orbit theorems, which gives a handle on singularities in the moduli space through mixed Hodge structures, and is related to a local notion of mirror symmetry thereby allowing us to apply it also to the large volume setting. These theorems are general and apply far beyond Calabi-Yau moduli spaces, leading us to propose that similarly the infinite distance structures we uncover are also more general.

A. Gheibi, H. Safari, D. E. Innes

Abstract We introduce analogue black holes (BHs) based on ideal magnetohydrodynamic equations. Similar to acoustic BHs, which trap phonons and emit Hawking radiation (HR) at the sonic horizon where the flow speed changes from super- to sub-sonic, in the horizon of magnetoacoustic and Alfvénic BHs, the magnetoacoustic and Alfvén waves will be trapped and emit HR made of quantized vibrations similar to phonons which we call magnephonons and Alphonons. We proposed that magnetoacoustic and Alfvénic BHs may be created in the laboratory using a tube with variable cross section embedded in a uniform magnetic field, and a super-magnetoacoustic or a super-Alfvénic flow. We show that the Hawking temperature for both BHs is a function of the background magnetic field, number density of fluid, and radius of the tube. For a typical setup, the temperature is estimated to be about 0.0266 K.

Martin Theaker

J Luis Egido

We present an overview of different beyond mean field theories (BMFTs) based on the generator coordinate method (GCM) and the recovery of symmetries used in many body nuclear physics with effective forces. In a first step a short reminder of the Hartree–Fock–Bogoliubov (HFB) theory is given. A general discussion of the shortcomings of any mean field approximation (MFA), stemming either from the lack of the elementary symmetries (like particle number and angular momentum) or the absence of fluctuations around the mean values, is presented. The recovery of the symmetries spontaneously broken in the HFB approach, in particular the angular momentum, is necessary, among others, to describe excited states and transitions. Particle number projection is also needed to guarantee the right number of protons and neutrons. Furthermore a projection before the variation prevents the pairing collapse in the weak pairing regime. A whole chapter is devoted to illustrate with examples the convenience of recovering symmetries and the differences between the projection before and after the variation. The lack of fluctuations around the average values of the MFA is a big shortcoming inherent to this approach. To build in correlations in BMFT one selects the relevant degrees of freedom of the atomic nucleus. In the low energy part of the spectrum these are the quadrupole, octupole and the pairing vibrations as well as the single particle degrees of freedom. In the GCM the operators representing these degrees of freedom are used as coordinates to generate, by the constrained (projected) HFB theory, a collective subspace. The highly correlated GCM wave function is finally written as a linear combination of a projected basis of this space. The variation of the coefficients of the linear combination leads to the Hill–Wheeler equation. The flexibility of the GCM Ansatz allows to describe a whole palette of physical situations by conveniently choosing the generator coordinates. We discuss the classical β and γ vibrations by considering the quadrupole operators as coordinates. We present pairing fluctuations by considering the pairing gaps as generator coordinates. The combination of quadrupole and pairing fluctuations mirrors the elementary modes of excitation of the atomic nucleus and provides a realistic description of it. Lastly the explicit consideration of the time reversal symmetry breaking in the HFB wave function by the cranking procedure allows the alignment of nucleon pairs opening a new dimension in the BMFT calculations. Abundant calculations with the finite range density dependent Gogny force applied to exotic nuclei illustrate the state-of-the-art of BMFTs with nuclear density functionals. We conclude with a thorough discussion on the potential poles of the theory.