Physics of Particles and Nuclei最新文献

The ΛCDM standard model of cosmology involves two dark components of the universe, dark energy, and dark matter. Whereas dark energy is usually associated with the (positive) cosmological constant Λ associated with a de Sitter geometry, we propose to explain dark matter as a pure QCD effect, namely a gluonic Bose–Einstein condensate with the status of a Cosmic Gluonic Background (CGB). This effect is due to the trace anomaly viewed as an effective negative cosmological constant determining an Anti de Sitter geometry and accompanying baryonic matter at the hadronization transition from the quark gluon plasma phase to the colorless hadronic phase. Our approach also allows to assume a ratio Dark/Visible equal to 11/2.

We discuss the distribution of fireballs produced in heavy-ion collisions in the net-baryon number and argue that neither the Free-Quark Model (FQM) nor the Hadron Resonance Gas (HRG) model can provide a comprehensive explanation of the distribution observed at the LHC. The concept of net-baryon number freezeout temperature is suggested and the role of sea quarks as a possible source of net-baryon number fluctuations is emphasized.

Researchers working in lattice field theory constitute an established community since the early 1990s, and around the same time the online open-access e-print repository arXiv was created. The fact that this field has a specific arXiv section, hep-lat, which is comprehensively used, provides a unique opportunity for a statistical study of its evolution over the last three decades. We present data for the number of entries, (E), published papers, (P), and citations, (C), in total and separated by nations. We compare them to six other arXiv sections (hep-ph, hep-th, gr-qc, nucl-th, quant-ph, cond-mat) and to two socio-economic indices of the nations involved: the Gross Domestic Product (GDP) and the Education Index (EI). We present rankings, which are based either on the Hirsch Index H, or on the linear combination (Sigma = E + P + 0.05C). We consider both extensive and intensive national statistics, i.e., absolute and relative to the population or to the GDP.

It is shown that the dense population of the early universe with well developed galaxies and supermassive black holes (quasars), observed by HST and JWST, nicely fits the conjecture that the galaxies and quasars are seeded by primordial black holes (PBHs), proposed in our work more than 30 years ago. This idea of galaxy seeding by massive black holes is rediscovered in recent publications by several groups. The predicted log-normal mass spectrum of PBHs very well agrees with the observations. Our other prediction of noticeable amount of antimatter in the Galaxy is also confirmed by the data.

We present and discuss well known conditions for ultraviolet finiteness. The requirements for complete absence of ultraviolet divergences in quantum field theories and existence of a non-trivial fixed point for renormalization group flow in the ultraviolet regime are compared based on the example of a six-derivative quantum gravitational theory in (d = 4) spacetime dimensions. Here vanishing of beta functions is equivalent to the emergence of conformal symmetry on the quantum level. In this model, it is possible for the first time to have fully UV-finite quantum theory without adding matter or special symmetry, but by inclusion of additional terms cubic in curvatures. We discuss all necessary algebraic conditions for this to happen. Finally, we motivate the claim that actually asymptotic safety needs UV-finite models for providing explicit form of the ultraviolet limit of Wilsonian effective actions describing special situations at conformal fixed points.

We review a class of exact solutions of Einstein’s equations in the presence of a scalar field that has three free parameters and become Janis–Newman–Winicour (JNW) metric and γ metric in a certain limit of parameters [1]. We also explain the rotating form of the class of axially symmetric metrics, which contain the rotating gamma and JNW metrics and the Bogush–Gal’tsov (BG) metric at certain values of the parameters [2].

The NA64 experiment at the CERN SPS is primarily designed for a search for Light Dark Matter (LDM) particles and corresponding mediators, the most popular of which is a vector boson A' (Dark Photon) kinetically mixed with the ordinary photon. However, other types of mediators and more complex models are also possible. The main search method is a missing energy technique. The sensitivity reached with (9.37 times {{10}^{{11}}}) electrons on its active target allowed to establish the best to-date limits on the LDM models parameters and partly cover the regions predicted by Thermal Dark Matter models that are well cosmologically motivated. Other directions of search for Feebly Interacting Particles (FIP) by NA64 are listed.

A brief overview of electromagnetic properties and the history of research on neutrino oscillations is presented. New phenomena in flavor and spin oscillations of neutrinos in a magnetic field and moving matter are discussed. In particular, we predict a new phenomena of changing the avour neutrino oscillations probability in moving matter, which may be engendered by a non-vanishing transverse matter current.

We give minireview of nonlocal field theory (infinite derivative field theory). We start with the discussion of the main peculiarities of nonlocal field theory on the example of (d = 4) scalar ({{phi }^{4}})-model. The nonlocal ({{phi }^{4}})-model is ultraviolet finite, unitary, and macrocausal. One of the problems of nonlocal field theory is that the formfactor is an arbitrary entire function that makes the predictions extremely weak. We propose some additional principle that allows to fix the formfactor. Also we review the main results obtained in nonlocal quantum gravity, namely the nonlocal generalization of Einstein gravity leads to the superrenormalizable theory.

Within the framework of a broadly Wittgensteinian approach, we criticize metaphysical realism, structural realism and Platonism in philosophy of physics and propose to replace them with what we call “contextual scientific realism.” According to this position, ontology is sensitive to context. Our view is illustrated with both ordinary and physical examples. In particular, we claim that the Higgs boson is a contextual entity within the framework of the Standard Model and the practice of its application, and that, in a sense, the nature of gravitational waves depends on the choice of a physical theory to describe them. A physical theory is interpreted as a Wittgensteinian rule (norm) for measuring physical reality within the language games if its applications. Contextual scientific realism explains the success of our best scientific theories and (dis)solves the problem of pessimistic meta-induction.