abstract

A five-dimensional Kaluza–Klein spacetime model is considered, with one extra compactified spatial dimension. The equation of state of an electrically-neutral, zero-temperature Fermi gas with a repulsive linear potential is described. From the equation of state, the speed-of-sound squared is calculated and shown for different model parameters. Its properties are studied from lower energies up to the conformal limit.

abstract

In this paper, I investigate whether spin precession — and consequently, orbital precession — is an artifact of the post-Newtonian radiation reaction (PN-RR) terms in CBWaves. To address this question, I conducted multiple simulations with CBWaves and compared the resulting orbits of the binary components. Alongside the inclusion of radiation-reaction terms, the initial eccentricity (\(e_{\mathrm {init}}\)), dimensionless spin magnitudes (\(\chi _{1,2}\)), and spin angles (\(\alpha \) and \(\beta \)) were systematically varied in the simulation loop to explore all possible contributing factors. The analysis of the resulting orbits indicates that radiation-reaction terms alone cannot fully account for the observed phenomenon.

abstract

Axion-like particles (ALPs) are often considered good candidates for dark matter (DM). Several mechanisms for generating the relic abundance of ALP DM have been proposed, involving processes that may occur either before, during, or after cosmic inflation. In all cases, the potential of the corresponding Peccei–Quinn (PQ) field plays an essential role. We investigate the radiative, thermal, and space-time curvature corrections to the PQ field dynamics in scenarios where the potential exhibits very small self-coupling. We focus on toy models with a quasi-supersymmetric spectrum and discuss how accounting for these corrections is crucial for obtaining reliable predictions for the relic abundance of ALP DM.

abstract

\(\alpha \)-attractors is a very promising class of inflationary models, utilizing a non-canonical form of the kinetic term to solve the problem of flatness of the potential. This mechanism has significant implications for the dynamics of the (p)reheating. In the current manuscript, we extend past studies of the simple \(\alpha \)-attractor T-model (in linear approximation) to the recently proposed \(\alpha \)-attractor hypernatural T-model.

abstract

We review the status of thermal leptogenesis in the minimal \(\mathrm {SU}(5)\times \mathrm {U}(1)\) and \(\mathrm {SO}(10)\) unified models under the assumption that the leptonic asymmetry generated in the out-of-equilibrium decays of heavy Majorana neutrinos (and its subsequent conversion into baryons via sphalerons) constitutes the primary source of baryon asymmetry of the Universe. In both cases, leptogenesis is shown to provide a strong extra constraint on the flavour structure of the model under consideration, leading to interesting and potentially testable phenomenological effects.

abstract

By considering an ansatz for \((1+(3+n))\)-dimensional static spacetime with three-dimensional spherical symmetry, we find different classes of vacuum solutions of Einstein field equations. A class of solutions with nontrivial extension of the Schwarzschild spacetime with extra dimensions features unusual properties, which may provide a possibility to address problems of dark matter and dark energy.

abstract

We investigated the use of a U-Net convolutional neural network for denoising simulated medium-resolution stellar spectroscopic observations, generated under realistic observational conditions resembling the Subaru Prime Focus Spectrograph (PFS). We found that our U-Net model effectively captured spectral features, achieving an average relative error of around \(1\%\) across diverse stellar parameters, despite a limited training set of only \(1000\) observations and a relatively short training period. Although U-Net did not reach the performance previously demonstrated by denoising autoencoders (DAEs) trained extensively on larger datasets, it outperformed DAEs trained under similarly constrained conditions. These results indicate that the U-Net architecture offers rapid, robust feature learning and may be particularly advantageous in scenarios involving initial denoising, subsequently refined by more accurate, but otherwise slower deep-learning models.

abstract

In these proceedings, we report on the latest searches for cosmology and New Physics with the NANOGrav 15-year dataset. We focus on the model-independent running of the spectral index and comment on the cosmic-inflation interpretations reported in previous NANOGrav Collaboration papers.

abstract

We studied the Euler–Poisson equation system in the case of cylindrical symmetry with the von Neumann–Sedov–Taylor-type of self-similar ansatz and present scaling solutions. We have analysed the scenario governed by Chaplygin’s equation of state, which has historically been studied as a unifying framework of dark fluid for dark matter and dark energy.

abstract

We compute asymptotic thermodynamics in cold and dense quantum chromodynamics (QCD) matter occurring in neutron stars by employing a dynamical quark potential that implements asymptotic freedom, thereby reconciling the speed of sound and quark number susceptibility (QNS) with conformal invariance in the high-density limit, which the widely used equations of state in the COMPOSE database do not address.

abstract

We show that a class of NJL-like models fails to reproduce the expected conformal limit of the speed of sound, making them unsuitable for analyzing the equation of state of dense matter. We then demonstrate how this issue can be resolved within a simple dynamical quark model.

abstract

Since black holes lack a straightforward notion of geometrical volume due to their event horizon structure and coordinate dependence, various approaches have been proposed to introduce a meaningful geometric and thermodynamic volume. In this work, we investigate the stability conditions of AdS black holes with and without volume.

abstract

Recent measurements in high-multiplicity proton–proton (\(pp\)) and proton–lead (\(p\)–Pb) collisions have exhibited features reminiscent of those observed in lead–lead (Pb–Pb) collisions. Among them, the observed enhancement of strange particle production as a function of multiplicity remains poorly understood. In order to probe the underlying mechanisms behind this phenomenon, we differentiate between strange hadrons originating from jets and those arising from soft processes. This is attained by using angular correlations between high transverse momentum charged particles and strange hadrons for \(K^0_S\), \({\mit \Xi }\), and \(\phi \) in \(pp\) collisions at \(\sqrt {s} = 13\) TeV and \(p\)–Pb collisions at \(\sqrt {s_{NN}} = 5.02\) TeV. We observe that strangeness enhancement in small collision systems grows smoothly with charged-particle multiplicity and is predominantly driven by soft processes, while hard processes’ contributions remain comparatively small.

abstract

EuPRAXIA is an acronym meaning “European Plasma Research Accelerator with Excellence in Applications” which almost completely explains the goals and purposes of the project. EuPRAXIA aims at planning and constructing two state-of-the-art accelerator facilities based on current plasma accelerator technologies. Plasma-based accelerators make it possible to radically reduce the facility size and overall costs compared to current radio-frequency (RF) accelerators. The two planned facilities — the first is beam-driven and the second is laser-driven — are envisioned to provide electron beams in the energy range of 1–5 GeV, and with beam parameters and quality comparable to the existing RF machines. In the following, we give a short overview of the status of the project in February 2025. Finally, we give a short overview of the possible Hungarian contributions to the EuPRAXIA project.

abstract

In this paper, we investigate the transverse momentum spectra of charged particles in proton–proton collisions at the LHC using detailed event-by-event simulations with the PYTHIA 8 event generator. Rather than relying solely on average observables such as the mean transverse momentum, we analyse the full shape of the spectra across different charged-particle multiplicity intervals. Our results show that significant variations in spectral shape occur with increasing multiplicity, revealing a transition from soft to hard processes that is not captured by global mean values. Comparisons with other commonly used Monte Carlo models, including Herwig 7 and EPOS 4, demonstrate that while the mean values are broadly consistent across generators, the underlying spectral shapes differ.

abstract

The ALICE experiment is dedicated to studying the hot and dense nuclear matter created in heavy-ion collisions at the Large Hadron Collider. A crucial part of the ALICE physics programme is to study small collision systems, such as proton–proton and proton–lead collisions, and compare them with the heavy-ion ones in order to disentangle effects coming from individual nucleon–nucleon interactions or from cold nuclear matter. In this contribution, the results on light-flavour hadron production from small (\(pp\) and \(p\)–Pb) to large collision systems (Pb–Pb) at various energies measured by ALICE are reported.

abstract

Quarkonium bound states are especially promising candidates to test the probable quantum structure of space-time since they represent a system with a reasonably small characteristic distance. In this contribution, we insert this system in a 3-dimensional rotationally-invariant space which is composed of concentric fuzzy spheres of increasing radius called the fuzzy onion. Our aim is to extract some consequences of the space’s non-trivial structure on the quarkonia’s properties.

abstract

Multi-particle production has been under scrutiny in spontaneously broken scalar theories. In this article, the self-consistent Schwinger–Dyson equation is solved in the spectral representation, and the multi-scalar production rate is calculated. We find an amplitude growing quadratically with the energy, which leads to an asymptotically decreasing scalar propagator.

abstract

Light-flavour hadron production has been studied in \(pp\), \(p\)–Pb, Pb–Pb, and, most recently, in Xe–Xe collisions. In this work, the production of pions, kaons, (anti-)protons, \(\phi \) mesons, \(K^{0}_{\mathrm {S}}\), \({\mit \Xi }\), and \({\mit \Omega }\) at midrapidity in Xe–Xe collisions at \(\sqrt {s_{NN}} = 5.44\) TeV is presented. Comparison of Xe–Xe and Pb–Pb collision systems at similar multiplicities can bring us new information about the behavior of systems with different initial geometrical eccentricities. Results show that integrated yields of strange particles increase with the charged-particle multiplicity.

abstract

We undertake the issue of flavor symmetries in the context of lepton masses and mixing which can lead to possible signatures in the current and future experiments at the intensity, energy, and cosmic frontiers. Giving an example of the \(A_4\) discrete symmetry, we show how to construct corresponding neutrino mass terms, leading to neutrino mass and mixing matrices with suitable correlations between parameters and unique phenomenological predictions.

abstract

In high-energy heavy-ion collisions, a strongly coupled, hot and dense medium is created. Direct photon measurements are excellent probes to study the time evolution and the equation of state of this peculiar matter. In this work, I describe the thermal radiation of the medium using a new analytic hydrodynamic model and apply an equation of state, which I have constrained based on the lattice QCD equation of state. I also compare the model with recent PHENIX measurements.

abstract

The Covariant Confined Quark Model is a reputed theoretical model acknowledged by important experimental groups. We provide a short overview of the model including several selected results.

abstract

The analysis of the early LHC Run 3 data was performed. Efficiencies for the ATLAS Forward Proton (AFP) Time-of-Flight (ToF) detector were studied. Performance studies of the ToF data included the proton–proton vertex reconstruction using matching of ToF and central ATLAS vertex position. After a calibration, a preliminary resolution of the vertex reconstruction was determined with a low-\(\mu \) ATLAS run.

abstract

The neutral Standard Model Higgs boson was discovered in 2012 at CERN, and the search for further particles of extended models continues, in particular, the search for an axion-like particle (ALP). Using machine learning technologies, this analysis addresses the separation of ALP production from unwanted background reactions. In this project, the Run 2 data from the ATLAS detector are used and the efficiency as well as the significance of the machine learning algorithm are optimized as a function of the theoretical ALP mass.

abstract

We investigate a general U\((1)_X\) scenario where we introduce three generations of Standard Model (SM) singlet right-handed neutrinos (RHNs) to generate the light neutrino mass through the seesaw mechanism after the breaking of U\((1)_X\) and electroweak symmetries. In addition to that, a general U\((1)_X\) scenario involves an SM-singlet scalar field and due to the U\((1)_X\) symmetry breaking, the mass of a neutral beyond the SM (BSM) gauge boson \(Z^\prime \) is evolved. The RHNs, being charged under the U\((1)_X\) scenario, can explain the origin of the observed baryon asymmetry through the resonant leptogenesis process. Applying observed neutrino oscillation data, we study \(Z^\prime \) and BSM scalar-induced processes to reproduce the observed baryon asymmetry. Hence, we estimate bounds on the U\((1)_X\) gauge coupling and the mass of the \(Z^\prime \) for different U\((1)_X\) charges and benchmark masses of RHN and SM-singlet scalar. Finally, we compare our results with limits obtained from the existing limits from LEP-II and LHC.

abstract

We introduce a novel way to represent the parameter space for U(1) extensions of the Standard Model. In our framework, the free parameters include the mass \(M_{Z'}\) of the new neutral gauge boson \(Z'\), the associated gauge coupling (or, equivalently, the mixing angle between the Standard Model \(Z\) and the new \(Z'\) boson), and a suitably chosen ratio of the new U(1) gauge charges. Recent experimental data allow us to constrain these parameters over an approximate \(Z'\) mass range of \((10^{-2},10^4)\) GeV/\(c^2\). We also examine the role of the tree-level \(\rho \) parameter as an indirect constraint and discuss the prospects for \(Z'\) searches at future colliders.

abstract

In this contribution, we give a brief overview of the status of perturbative quantum chromodynamics calculations and some recent advances in computational techniques. We also touch on one particular determination of the strong coupling constant and highlight the important role played by precise perturbative calculations in this measurement.

abstract

Although the QCD instanton has been intensively searched for in several experiments, it has not yet been observed. Here, we study the possibility of observing heavy (\(M_{\rm inst}\gt 60\) GeV) QCD instantons at the LHC in the diffraction mode, i.e. in events with one or two tagged leading protons which are accompanied by large rapidity gaps. The presented analysis provides a detailed look into the experimental situation and accounts for detector and pile-up effects. We show that the expected instanton signal in a single-tagged configuration is strongly affected by central detector and pile-up effects but observable. For the double-tagged approach, the combinatorial background overwhelms the expected signal. Possible improvements lie in adding time information about tracks at central and forward rapidities.

abstract

The superweak force is a minimal, anomaly-free U(1) extension of the Standard Model, designed to explain the origin of (i) neutrino masses and mixing matrix elements, (ii) dark matter, (iii) cosmic inflation, (iv) stabilization of the electroweak vacuum, and (v) leptogenesis. In this paper, we discuss the phenomenological status of the model and provide viable scenarios for the physics of the items in this list.

abstract

We give an overview of recent developments in the computation of the anomalous dimension matrix of composite operators in non-forward kinematics. The elements of this matrix set the evolution of non-perturbative parton distributions such as the generalized parton distribution functions. The latter provide important information about hadronic structure and are accessible experimentally in hard exclusive scattering processes. We focus our discussion on a recent method that exploits consistency relations for the anomalous dimensions which follow from the renormalization structure of quark and gluon operators.

abstract

In order to numerically compute scattering cross sections in QCD, one needs to deal with various kinematic divergences that appear at intermediate stages of the calculation. One way of doing this is by setting up an IR subtraction scheme. In this paper, we give an update on the status of extending the CoLoRFul subtraction scheme, which has been successfully used in the past for processes with only final-state hadrons, to hadron–hadron collisions. In particular, we discuss the analytic computation of the integrated counterterms.

abstract

Heavy-flavor production at the LHC offers valuable tests of quantum-chromodynamics calculations, owing to the large masses of heavy quarks. Measurements of charm production as a function of event activity reveal new features of charm production and fragmentation, providing insights into the interplay between soft and hard processes. In addition, charm production in heavy-ion collisions addresses flavor-dependent quark transport properties in both hot and cold nuclear matter, helping to clarify the roles of coalescence and fragmentation in heavy-flavor hadron formation. This contribution summarizes recent measurements from the ALICE experiment on charm production as a function of charged-particle multiplicity in \(pp\) collisions at various energies, including the measurements of charm baryon-to-meson production yield ratios in \(pp\), \(p\)–Pb, and Pb–Pb collisions. New results on \({D}^0\) production in \(pp\) collisions as a function of the transverse spherocity of the event are also presented.

abstract

This article presents a recent QCD measurement of the jet cross-section ratios from the ATLAS experiment at CERN’s Large Hadron Collider, using proton–proton collisions at a center-of-mass energy of 13 TeV. The jet cross-section ratios are derived from multi-differential particle-level cross sections for several inclusive jet multiplicity bins for at least 2, 3, 4, and 5 jets. These ratios improve sensitivity to the strong coupling parameter while reduce sensitivity to uncorrelated systematic uncertainties and parton distribution functions. The three-to-two jet cross-section ratio is reported for the first time at 13 TeV center-of-mass energy. Additionally, higher jet multiplicity ratios are measured experimentally for the first time, providing a crucial reference for future theoretical developments in high-precision QCD predictions involving multiple jets.