The synthesis of the light Mo and Ru isotopes: how now, no need for an exotic solution ?

The most detailed calculations of the p-process call for its development in the O/Ne layers of Type II supernovae. In spite of their overall success in reproducing the solar system content of p-nuclides, they suggest a significant underproduction of the light Mo and Ru isotopes. On grounds of a model for the explosion of a 25 solar mass star with solar metallicity, we demonstrate that this failure might just be related to the uncertainties left in the rate of the 22Ne(alpha,n)25Mg neutron producing reaction. The latter indeed have a direct impact on the distribution of the s-process seeds for the p-process.Comment: 4 pages, 4 figures. LaTex2e with aa.cls. A&A Letters, in pres

Dilution of zero point energies in the cosmological expansion

The vacuum fluctuations of all quantum fields filling the universe are supposed to leave enormous energy and pressure contributions which are incompatible with observations. It has been recently suggested that, when the effective nature of quantum field theories is properly taken into account, vacuum fluctuations behave as a relativistic gas rather than as a cosmological constant. Accordingly, zero-point energies are tremendously diluted by the universe expansion but provide an extra contribution to radiation energy. Ongoing and future cosmological observations could offer the opportunity to scrutinize this scenario. The presence of such additional contribution to radiation energy can be tested by using primordial nucleosynthesis bounds or measured on Cosmic Background Radiation anisotropy.Comment: 8 pages, no figures. Submitted the 17th of March to Modern Physics Letters

Comment on "Feynman Effective Classical Potential in the Schrodinger Formulation"

We comment on the paper "Feynman Effective Classical Potential in the Schrodinger Formulation"[Phys. Rev. Lett. 81, 3303 (1998)]. We show that the results in this paper about the time evolution of a wave packet in a double well potential can be properly explained by resorting to a variational principle for the effective action. A way to improve on these results is also discussed.Comment: 1 page, 2eps figures, Revte

Working remotely during the COVID-19 pandemic: Work-related psychosocial factors, work satisfaction, and job performance among Russian employees

Background. The spread of COVID-19 has forced organizations to quickly offer remote work arrangements to employees. Objective. The study focuses on remote work during the first wave of the pandemic and describes how russian employees experienced remote work. The research has three main objectives: (1) to investigate the influence of gender and age on employees' perceptions of remote work; (2) to investigate the relationship between remote work and psychosocial variables, such as remote work stress, remote work engagement, and family-work conflict; (3) to examine whether and how much such psychosocial factors are related to remote work satisfaction and job performance. These objectives were the basis for developing six hypotheses. Design. a cross-sectional study involved 313 russian employees. Data were collected using an online survey distributed in april and May 2020. The hypotheses were tested using ANOVA, correlations, and multiple linear regression analyses. Results. Women experienced more stress and more engagement when working remotely; older employees perceived remote work as a less positive experience; opinions about remote work and remote work engagement were positively related to remote work satisfaction; Leader-Member Exchange (LMX) was a significant predictor of job performance. Conclusion. During the lockdown, remote work was perceived as a positive experience. We discuss some practical implications for organizations and managers

Nonuniform symmetry breaking in noncommutative λΦ4\lambda \Phi^4 theory

The spontaneous symmetry breaking in noncommutative $\lambda\Phi^4$ theory has been analyzed by using the formalism of the effective action for composite operators in the Hartree-Fock approximation. It turns out that there is no phase transition to a constant vacuum expectation of the field and the broken phase corresponds to a nonuniform background. By considering $=A \cos(\vec Q \cdot \vec x)$ the generated mass gap depends on the angles among the momenta $\vec k$ and $\vec Q$ and the noncommutativity parameter $\vec\theta$. The order of the transition is not easily determinable in our approximation.Comment: 18 pages, 4 figures, added reference

On the V-type asteroids outside the Vesta family. I. Interplay of nonlinear secular resonances and the Yarkovsky effect: the cases of 956 Elisa and 809 Lundia

Among the largest objects in the main belt, asteroid 4 Vesta is unique in showing a basaltic crust. It is also the biggest member of the Vesta family, which is supposed to originate from a large cratering event about 1 Gyr ago (Marzari et al. 1996). Most of the members of the Vesta family for which a spectral classification is available show a V-type spectra. Before the discovery of 1459 Magnya (Lazzaro et al. 2000) and of several V-type NEA (Xu 1995), all the known V-type asteroids were members of the Vesta family. Recently two V-type asteroids, 809 Lundia and 956 Elisa, (Florczak et al. 2002) have been discovered well outside the limits of the family, near the Flora family. We currently know 22 V-type asteroids outside the family, in the inner asteroid belt. In this work we investigate the possibility that these objects are former family members that migrated to their current positions via the interplay of Yarkovsky effect and nonlinear secular resonances. The main dynamical feature of 956 Elisa and 809 Lundia is that they are currently inside the 2(g-g6)+s-s6 (z2 by Milani and Knezevic, 1993) secular resonance. Our investigations show that members of the Vesta dynamical family may drift in three-body and weak secular resonances until they are captured in the strong z2 secular resonance. Only asteroids with diameters larger than 16 km can remain in one of the three-body or secular resonances long enough to reach the region of the z2 resonance. This two-step mechanism of capture into the z2 resonance could explain: i) the current resonant orbits of 956 Elisa and 809 Lundia, ii) why their size is significantly larger than that of the typical member of the Vesta family, and iii) provide a lower limit on the Vesta family age.Comment: 14 pages, 10 figures, 3 tables. Accepted for publication in A&

The s-process weak component: uncertainties due to convective overshooting

Using a new s-nucleosynthesis code, coupled with the stellar evolution code Star2003, we performed simulations to study the impact of the convection treatment on the s-process during core He-burning of a 25 Msun star (ZAMS mass) with an initial metallicity of Z=0.02. Particular attention was devoted to the impact of the extent of overshooting on the s-process efficiency. The results show enhancements of about a factor 2-3 in s-process efficiency (measured as the average overproduction factor of the 6 s-only nuclear species with $60\lesssim A\lesssim 90$) with overshooting parameter values in the range 0.01-0.035, compared to results obtained with the same model but without overshooting. The impact of these results on the p-process model based on type II supernovae is discussed.Comment: 7 pages, 4 figures, accepted for publication in Astronomy & Astrophysic

Identifying Near Earth Object Families

The study of asteroid families has provided tremendous insight into the forces that sculpted the main belt and continue to drive the collisional and dynamical evolution of asteroids. The identification of asteroid families within the NEO population could provide a similar boon to studies of their formation and interiors. In this study we examine the purported identification of NEO families by Drummond (2000) and conclude that it is unlikely that they are anything more than random fluctuations in the distribution of NEO osculating orbital elements. We arrive at this conclusion after examining the expected formation rate of NEO families, the identification of NEO groups in synthetic populations that contain no genetically related NEOs, the orbital evolution of the largest association identified by Drummond (2000), and the decoherence of synthetic NEO families intended to reproduce the observed members of the same association. These studies allowed us to identify a new criterion that can be used to select real NEO families for further study in future analyses, based on the ratio of the number of pairs and the size of strings to the number of objects in an identified association.Comment: Accepted for publication in Icarus. 19 pages including 11 figure

Noncommutativity and Lorentz Violation in Relativistic Heavy Ion Collisions

The experimental detection of the effects of noncommuting coordinates in electrodynamic phenomena depends on the magnitude of |\theta B|, where \theta is the noncommutativity parameter and B a background magnetic field. With the present upper bound on \theta, given by \theta_{\rm bound} \simeq 1/(10 {\rm TeV})^2, there was no large enough magnetic field in nature, including those observed in magnetars, that could give visible effects or, conversely, that could be used to further improve \theta_{\rm bound}. On the other hand, recently it has been proposed that intense enough magnetic fields should be produced at the beginning of relativistic heavy ion collisions. We discuss here lepton pair production by free photons as one kind of signature of noncommutativity and Lorentz violation that could occur at RHIC or LHC. This allows us to obtain a more stringent bound on \theta, given by 10^{-3} \theta_{\rm bound}, if such "exotic" events do not occur.Comment: Five pages, no figures

ϵ\epsilon-Expansion of the Conductivity at the Superconductor-Mott Insulator Transition

We study the critical behavior of the conductivity $\sigma(\omega)$ at the zero temperature superconductor-Mott insulator transition in $d$ space-time dimensions for a model of bosons with short-range interaction and no disorder. We obtain $\sigma(\omega_n ) = (4e^2/\hbar) \sigma_{\epsilon} \omega_n^{1-\epsilon}$, as predicted by the scaling theory, and the prefactor $\sigma_{\epsilon}$ is calculated in the $\epsilon$-expansion, to order $\epsilon ^2$ ($\epsilon = 4-d$). In two spatial dimensions, ($d=3$), we find a value of the universal conductance $\sigma^\star =0.315 (4e^2/h)$, in good agreement with the known Monte Carlo results.Comment: 8 pages REVTE