The European Physical Journal C最新文献

Photon flux benchmark models together with recent experimental estimations for pomeron energy fluxes and structure functions are implemented within Monte Carlo simulation, to determine their impact on physical observables and on the signal strength uncertainty of the yet-to-be observed semi-exclusive (tbar{t}) production in proton–proton (pp) collisions at Large Hadron Collider (LHC) and Future Circular Collider (FCC) energies. Expected cross-section rises by a factor of (sim 50) and (sim 22) for pomeron-induced and photon-induced processes respectively from LHC to FCC energy regime. TensorFlow deep neural networks were implemented to discriminate semi-exclusive processes against non-peripheral (tbar{t}X) background, achieving an Area Under the Curve (AUC) test performance of (0.9917 pm 0.0002) for the photon-induced signal. At detector level, following the geometry of the CMS detector at CERN, the minimum Hadronic Forward energy observable was identified as the most effective discriminator against non-peripheral (tbar{t}X) background. In the context of low pileup pp data and based on the Asimov dataset, by considering the statistical effects and the systematic contribution from pomeron/photon schemes to the total uncertainty a 5-(sigma ) significance is expected for pomeron-induced and photon-induced (tbar{t}) production modes with 1 fb(^{-1}) and 4.7 fb(^{-1}) integrated luminosity datasets respectively. The systematic contribution to the total uncertainty is 25.1% and 7.6% respectively, highlighting the potential for experimental observation using Run 2 and Run 3 LHC data, allowing further studies within the LHC forward physics program.

We investigate quasinormal modes (QNMs) of scalar, electromagnetic, and axial gravitational perturbations in slowly rotating Kalb–Ramond (KR) black holes, where an antisymmetric tensor field induces spontaneous Lorentz symmetry breaking. Working consistently to first order in the dimensionless spin parameter, we derive the corresponding master equations and compute the QNM spectrum using both the continued-fraction and matrix methods, finding excellent agreement. Lorentz violation modifies the oscillation and damping rates in a unified manner across all perturbative sectors: the real part of the QNM frequency increases monotonically with the Lorentz-violating parameter (ell ), while the imaginary part becomes more negative. Axial gravitational modes exhibit the strongest response, revealing an intrinsic theoretical bound (ell < 0.5), beyond which the spectrum approaches an extremal behavior. Our results highlight the potential of gravitational-wave spectroscopy to probe Lorentz-violating signatures in KR gravity.

In this paper, we adopt continued fraction method (CFM) associated with VBK approach, which is recently developed by Vieira, Bezerra and Kokkotas, to investigate the spectrum of quasibound states (QBS) and superradiant instability of massive scalar perturbation imposed on analog rotating black hole in photon-fluid model. We analyze the effects of black hole angular velocity (Omega _H) and scalar field mass (mu ) on QBS spectrum with positive and negative winding number (m=pm 1), respectively. In addition to the fundamental frequency, we also investigate the overtones in order to disclose more distinctions of spectrum between the states of (m=pm 1). We show that the sign of winding number can produce notable impacts on the spectrum, particularly to the imaginary part of the spectrum. We study the superradiant instability and find that the maximum instability for a given (Omega _H) is not in monotonic relationship with angular velocity, which is in contrast to the case in Kerr black hole spacetime. As expected, the strength of superradiant instability can be significantly weakened by increasing the winding number. These findings imply that there exists a critical angular velocity under which the instability is strongest in parameter space, and we are supposed to find it out at (m=1). Indeed, this max instability is found to be (omega _{Imax}approx 1.13374times 10^{-5}) related to the critical angular velocity (Omega _Happrox 1.22).

We investigate behaviour of brane backgrounds under poly-vector deformations in Type IIB and D = 11 supergravities. We find that the standard bi-vector deformations add dissolved F1 string charge to a Dp-brane background, quadri-vector deformations add D3-brane charge, tri- and six-vector deformations in D = 11 add M2- and M5-brane charges respectively. We discuss these results in the context of NRCS and OM theories.

We examine non-singular bounce cosmology within the framework of a phantom scalar field coupled to the Gauss–Bonnet term in both non-viscous and bulk-viscous cases. Using the scale factor ansatz (alpha (t)=left( frac{alpha }{eta }+t^2right) ^{frac{1}{2 eta }}), we reconstruct the scalar field potential V(t), and observe a smooth potential well centered at the bounce point. The resulting energy density, pressure, and equation-of-state parameter show NEC violation necessary for successful bounce, while viscosity controls post-bounce dynamics with a positive and smooth squared speed of sound. In contrast, for the non-viscous model, sharp divergences occur just at the bounce and continues to be negative in the expanding phase, which in turn emphasises the stabilising role of dissipative effects. The energy condition analysis indicates a temporary NEC and SEC violation in the viscous scenario, whereas its persistent violation within the non-viscous model suggests a continuous accelerated expansion. Observational viability is found through Bayesian MCMC fitting in regards to the Pantheon+ supernova data, with best-fit parameters providing a reduced chi-squared of (chi _{red}^2 =0.995) while the inflation observables derived from the reconstructed potential place our model predictions inside (68%) CL Planck 2018 confidence contours. Our findings suggest that bounce cosmologies could offer a physically reasonable and observationally acceptable alternative or pre-inflationary scenario, while highlighting the role that viscosity could play for a stable and smooth cosmological evolution.

Unitary transformations are employed to enhance the violations of the Bell-CHSH inequality in relativistic quantum field theory. The case of the scalar field in (1+1) Minkowski space-time is scrutinized by relying on the Tomita–Takesaki modular theory. The example of the bounded Hermitian operator (sign(varphi (f))), where (varphi (f)) stands for the smeared scalar field, is worked out. It is shown that unitary deformations enable for violations of the Bell-CHSH inequality. The setup is generalized to the Proca vector field by means of its equivalence with the scalar theory.

This paper investigates the dynamical behavior of a quintom dark energy model, which combines quintessence and phantom scalar fields, across four distinct interacting scenarios: (I) quintessence-matter interaction, (II) phantom-matter interaction, (III) coupled quintessence-phantom-matter interaction, and (IV) intra-dark energy interaction (quintessence-phantom energy exchange). By constructing autonomous dynamical systems for each case, we analyze the stability of critical points and evaluate the cosmological evolution using the statefinder diagnostic pair ({r, s}). The exponential potentials for both scalar fields and interaction terms proportional to the matter density ((Q_1, Q_2)) are adopted to derive fixed points, revealing that all scenarios admit late-time phantom-dominated attractors, consistent with accelerated expansion. Notably, interactions between dark sectors significantly alter transient regimes: energy transfer from dark matter to dark energy prolongs matter-quintessence coexistence phases, while reverse transfer accelerates phantom dominance. The statefinder diagnostic, however, fails to distinguish interactions due to overlapping (s-r) trajectories across cases. Numerical simulations further demonstrate epochs of negative phantom energy density in scenarios involving phantom coupling, linked to non-physical fixed points. These results highlight quintom’s flexibility in mimicking observed dark energy behavior while emphasizing the limited discriminatory power of ({r, s}) for coupling-specific dynamics. The study underscores the role of interactions in alleviating cosmic coincidence problems and shaping multi-phase cosmic histories.

In the recent years, argon-based experiments looking for Dark Matter in the Universe have explored the non-standard scenario in which Dark Matter is made by low-mass Weakly Interacting Massive Particles, of mass in the range of 1–10 GeV instead of the canonical hundreds of GeV. Detecting such particles is challenging, as their expected signatures are nuclear recoils with energies below 10 keV, observable solely via ionization. This necessitates a precise understanding of the detector response in this energy regime, which remains incomplete for argon. To address this, the ReD experiment was developed within the framework of the DarkSide-20k Collaboration to produce and characterize few-keV nuclear recoils. A compact dual-phase argon Time Projection Chamber (TPC) was irradiated with neutrons from a (^{252})Cf source, to produce Ar recoils in the energy range of interest via (n,n’) elastic scattering. A downstream spectrometer composed of 18 plastic scintillators detected the neutrons scattered off Ar nuclei, enabling recoil energy reconstruction via two-body kinematics. The ionization yield (Q_{y}) of argon, defined as the number of electrons produced per unit energy deposit, was measured in a model-independent way between 2 and 10 keV. These measurements extend direct experimental coverage well below the previous limit of approximately 7 keV. The results are consistent with existing data above 7 keV, while they indicate a higher (Q_{y}) at lower energies.

We develop a Heisenberg-picture kinematical framework in which (i) time is treated as a quantum observable, admitting both a relational POVM construction for semibounded spectra and a fully self-adjoint realization on an enlarged (conjugate-energy) Hilbert space enabled by a gravitational conjugation symmetry (mathcal {C}_g), and (ii) the generators of spacetime translations need not commute in curved backgrounds. The central postulate, ([,hat{x}_mu ,hat{P}_nu ]=textrm{i}hbar ,hat{g}_{mu nu }(hat{x})), makes the spacetime metric a metric operator defined by the symmetrized commutator. Jacobi identities close the algebra and imply an operator form of metric compatibility; in a worked FRW example we obtain ([,hat{P}_0,hat{P}_i]=2textrm{i}hbar ,N^2(t),H(t),hat{P}_i), which reduces to (2textrm{i}hbar ,H,hat{P}_i) in cosmic-time gauge (N=1), exhibiting Hubble–controlled non-commuting “translations.” A key structural ingredient is the symmetry (mathcal {C}_g): an antiunitary map that flips all translation generators, (hat{P}_mu !rightarrow !-Theta hat{P}_mu Theta ^{-1}), while covariantly transforming the metric and Lorentz sectors, leaving the canonical commutators and the [P, P] algebra invariant. We discuss uncertainty relations and show how metric-operator fluctuations can rescale primordial amplitudes; an explicitly labeled toy propagation of such a rescaling to high-z halo abundances is given in Appendix D.

We present the implementation of simplified and full likelihood models for multibin signal regions in CheckMATE. A total of 13 searches are included from ATLAS and CMS, and several methods are presented for the implementation and evaluation of likelihood functions. Statistical combinations increase the sensitivity of searches and open up the possibility of combining orthogonal search channels in the CheckMATE framework.