Kuntz, IbereCasadio, RobertoKamenshchik, Alexander
11页
查看更多>>摘要：The Hawking-Penrose theorem is not covariant under field redefinitions. Should the invariance under such transformations be a true principle in nature, spacetime singularities become dubious objects. We here review the concept of covariant singularities, that is, singularities that are invariant under both spacetime diffeomorphisms and field redefinitions.
查看更多>>摘要：In the planned ton-scale neutrinoless double beta (0 nu beta beta) decay experiments, the used Q value is the mass-energy difference between the ground states of mother and daughter atoms, without correcting the atomic energy difference due to the alteration in the nuclear charge before and after the decay process. We show that the atomic energy change between the two ground states can potentially reduce the Q value by 5.502, 12.103, and 12.372 keV for the decays from Ge-76, Te-130, and Xe-136, respectively. The available kinetic energy for two electrons can be 2033.51 keV for Ge-76 decay, 2515.41 keV for Te-130 decay, and 2445.45 keV for Xe-136 decay after correcting for atomic effects. This implies that the planned experiments could potentially miss the decay signature if a narrow energy window is designated to reduce background events including 2 nu beta beta decay events.
查看更多>>摘要：In this paper, a statistical model introducing analytical expressions of x dependent quantum statistical parton distributions is presented to explore proton and neutron structures. A merely theoretical maximum entropy method is applied to obtain thermodynamical variables determining parton distributions accurately. This study provides considering proton and neutron isospin asymmetry in order to improve the consistency of the framework achievements with the experimental results. The presented approach is extended to evaluate modified neutron structure in an n-p state. Also, the uniqueness of gluon distribution in proton and neutron is surveyed for both cases of lonely nucleon and n-p system. Eventually, the predicted unpolarized structure functions and the spin structure functions, only based on the maximum entropy method, are compared to CERN, HERMES, SLAC and the other data sets. Finally, the correlation of the obtained distributions with the experimental observations confirms the proposed statistical model.
查看更多>>摘要：In this paper, we constrain the primordial gravitational waves from cosmic microwave background (CMB) and stochastic gravitational wave background (SGWB) observations. SGWB provides the latest way to explore the early universe and the cosmological evolution which can be reflected by primordial gravitational waves. We not only combine LIGO observations with CMB to measure primordial gravitational waves, but also forecast the potential abilities of the LISA detector and PTA projects. In the Lambda CDM +r +n(t) model, the standard six parameters change slightly from SGWB observations. While the constraints on tensor-to-scalar ratio and tensor spectral index are improved obviously from SGWB observations. FAST projects have a significant impact on tensor-to-scalar ratio and tensor spectral index, namely r < 0.028 and n(t) = -0.41(-0.96)(+0.64) at 95% confidence level.
查看更多>>摘要：In this paper, we consider the scalar mode of gravity as expressed by a conformal factor of the metric and present a model motivated by the Jordan-Brans-Dicke action. The reduced action provides a Lagrangian density in Minkowski space which exhibits a massive particle and an expanding spacetime through a mechanism which is similar to the Higgs mechanism.
查看更多>>摘要：In this paper, we discuss the inflationary magnetogenesis scenario, in which the coupling function is introduced to break the conformal invariance of electromagnetic action. Unlike in conventional models, we deduce the Maxwell's equations under the perturbed Friedmann-Robertson-Walker metric. We found that the self-consistency of the action depends on the form of the coupling function when the scalar mode perturbations have been considered. Therefore, this self-consistency can be seen as a restriction on the coupling function. In this paper, we give the restrictive equation for coupling function then obtain the specific form of the coupling function in a simple model. We found that the coupling function depends on the potential of the inflaton and thus is model-dependent. We obtain the power spectrum of electric field and magnetic field in large-field inflation model. We also found that the coupling function is an increasing function of time during slow-roll era as most of inflationary magnetogenesis models, it will lead to strong coupling problem. This issue is discussed qualitatively by introducing a correction function during the preheating.
查看更多>>摘要：The "Krein" regularization method of quantum field theory is studied, inspired by the Krein space quantization and quantum metric fluctuations. It was previously considered in the one-loop approximation, and this paper is generalized to all orders of perturbation theory. We directly recover the physical results previously obtained starting from the standard QFT by imposing the renormalization conditions. By applying our approach to the QFT in curved spacetime and quantum linear gravity, we discuss that there is no need for the higher derivative of the metric tensor for the renormalization of the theory. The advantage of our method compared to the previous ones is that the linear quantum gravity is renormalizable in all orders of perturbation theory.
NSTL
World Scientific