Frontiers in Physics | High-Energy and Astroparticle Physics section | New and Recent Articles
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https://www.frontiersin.org/articles/10.3389/fphy.2021.762279
Thermal Correction to the Kinnersley Black Hole in a Lorentz-Violating Dirac Field Theory2021-11-29T00:00:00ZZhi-E. LiuJie ZhangShu-Zheng YangAccording to Lorentz-violating theory, the dynamical equation of Dirac particles in the Kinnersley black hole with variably accelerated linear motion is modified. The Hawking quantum tunneling radiation characteristics of Kinnersley black hole are obtained by solving the modified equation. The expression of the Hawking temperature of Kinnersley black hole has been updated.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.703266
https://www.frontiersin.org/articles/10.3389/fphy.2021.703266
Effect of Sterile Neutrino on Low-Energy Processes in Minimal Extended Seesaw With Δ(96) Symmetry and TM1 Mixing2021-08-16T00:00:00ZNayana GautamR. KrishnanMrinal Kumar DasWe study the effect of sterile neutrino on some low-scale processes in the framework of the minimal extended seesaw (MES). MES is the extension of the seesaw mechanism with the addition of sterile neutrino of intermediate mass. The MES model in this work is based on Δ(96) × C_{2} × C_{3} flavor symmetry. The structures of mass matrices in the framework lead to TM_{1} mixing with μ–τ symmetry. The model predicts the maximal value of the Dirac CP phase. We carry out our analysis to study the new physics contributions from the sterile neutrino to different charged lepton flavor violation (cLFV) processes involving muon and tau leptons as well as neutrinoless double beta decay (0νββ). The model predicts normal ordering (NO) of neutrino masses, and we perform the numerical analysis considering normal ordering (NO) only. We find that a heavy sterile neutrino can lead to cLFV processes that are within the reach of current and planned experiments. The sterile neutrino present in our model is consistent with the current limits on the effective neutrino mass set by 0νββ experiments.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.534265
https://www.frontiersin.org/articles/10.3389/fphy.2021.534265
Functorial Evolution of Quantum Fields2021-07-28T00:00:00ZStefano GogiosoMaria E. StasinouBob CoeckeWe present a compositional algebraic framework to describe the evolution of quantum fields in discretised spacetimes. We show how familiar notions from Relativity and quantum causality can be recovered in a purely order-theoretic way from the causal order of events in spacetime, with no direct mention of analysis or topology. We formulate theory-independent notions of fields over causal orders in a compositional, functorial way. We draw a strong connection to Algebraic Quantum Field Theory (AQFT), using a sheaf-theoretical approach in our definition of spaces of states over regions of spacetime. We introduce notions of symmetry and cellular automata, which we show to subsume existing definitions of Quantum Cellular Automata (QCA) from previous literature. Given the extreme flexibility of our constructions, we propose that our framework be used as the starting point for new developments in AQFT, QCA and more generally Quantum Field Theory.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.587083
https://www.frontiersin.org/articles/10.3389/fphy.2021.587083
Equivalence of Approaches to Relational Quantum Dynamics in Relativistic Settings2021-06-18T00:00:00ZPhilipp A. HöhnAlexander R. H. SmithMaximilian P. E. LockWe have previously shown that three approaches to relational quantum dynamics—relational Dirac observables, the Page-Wootters formalism and quantum deparametrizations—are equivalent. Here we show that this “trinity” of relational quantum dynamics holds in relativistic settings per frequency superselection sector. Time according to a clock subsystem is defined via a positive operator-valued measure (POVM) that is covariant with respect to the group generated by its (quadratic) Hamiltonian. This differs from the usual choice of a self-adjoint clock observable conjugate to the clock momentum. It also resolves Kuchař's criticism that the Page-Wootters formalism yields incorrect localization probabilities for the relativistic particle when conditioning on a Minkowski time operator. We show that conditioning instead on the covariant clock POVM results in a Newton-Wigner type localization probability commonly used in relativistic quantum mechanics. By establishing the equivalence mentioned above, we also assign a consistent conditional-probability interpretation to relational observables and deparametrizations. Finally, we expand a recent method of changing temporal reference frames, and show how to transform states and observables frequency-sector-wise. We use this method to discuss an indirect clock self-reference effect and explore the state and temporal frame-dependence of the task of comparing and synchronizing different quantum clocks.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.706197
https://www.frontiersin.org/articles/10.3389/fphy.2021.706197
Editorial: Black Holes, Extended Phase Space Thermodynamics and Phase Transitions2021-06-17T00:00:00ZChandrasekhar BhamidipatiMohamed ChababBehzad Eslam Panahhttps://www.frontiersin.org/articles/10.3389/fphy.2021.618392
https://www.frontiersin.org/articles/10.3389/fphy.2021.618392
CPTM Symmetry for the Dirac Equation and Its Extended Version Based on the Vector Representation of the Lorentz Group2021-06-01T00:00:00ZE. MarschY. NaritaWe revisit the CPT theorem for the Dirac equation and its extended version based on the vector representation of the Lorentz group. Then it is proposed that CPTM may apply to this fundamental equation for a massive fermion a s a singlet or a doublet with isospin. The symbol M stands here for reversing the sign of the mass in the Dirac equation, which can be accomplished by operation on it with the so-called gamma-five matrix that plays an essential role for the chirality in the Standard Model. We define the CPTM symmetry for the standard and extended Dirac equation and discuss its physical implications and some possible consequences for general relativity.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.666591
https://www.frontiersin.org/articles/10.3389/fphy.2021.666591
Brief Review of the Results Regarding the Possible Underlying Mechanisms Driving the Neutrinoless Double Beta Decay2021-05-21T00:00:00ZAndrei NeacsuVasile Alin SevestreanSabin StoicaSince the experimental discovery of neutrino oscillations, the search for the neutrinoless double beta (0νββ) decay has intensified greatly, as this particular decay mode, if experimentally discovered, could offer a testing ground for Beyond Standard Model (BSM) theories related to the yet hidden fundamental properties of neutrinos and the possibility of violating of some fundamental symmetries. In this work we make a brief review of the nuclear matrix elements and phase space factors calculations performed mainly by our group. Next, using these calculations and the most recent experimental half-life limits, we revise the constraints on the BSM parameters violating the lepton number corresponding to four mechanisms that could contribute to 0νββ decay. Finally, using the values obtained for the BSM parameters from one of the most sensitive double-beta decay experiments, we provide a comparison with the sensitivities of other experiments.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.686352
https://www.frontiersin.org/articles/10.3389/fphy.2021.686352
Editorial: Coarse Graining in Quantum Gravity: Bridging the Gap Between Microscopic Models and Spacetime-Physics2021-05-21T00:00:00ZAstrid EichhornBenjamin BahrAntonio D. Pereirahttps://www.frontiersin.org/articles/10.3389/fphy.2021.655857
https://www.frontiersin.org/articles/10.3389/fphy.2021.655857
Replacing the Notion of Spacetime Distance by the Notion of Correlation2021-05-19T00:00:00ZAchim KempfSpacetime is conventionally viewed as a stage on which actors, in the form of massive and massless matter, move. In this study, we explore what may lie beyond this picture. The starting point is the observation that quantum field fluctuations are the more strongly correlated the shorter their spacetime distance. The notion of spacetime distance can, therefore, be replaced by the notion of correlation strength. This suggests a new picture in which the abstract 2-point and multi-point correlations are the primary structure, a picture which is essentially information-theoretic. In the low energy regime, the secondary notions of spacetime and of matter would then emerge as approximate representations of the abstract correlators, namely, in the form of Feynman rules on curved spacetime.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.666286
https://www.frontiersin.org/articles/10.3389/fphy.2021.666286
Corrigendum: On the Possibility of Experimental Detection of the Discreteness of Time2021-04-28T00:00:00ZMarios ChristodoulouCarlo Rovellihttps://www.frontiersin.org/articles/10.3389/fphy.2021.666041
https://www.frontiersin.org/articles/10.3389/fphy.2021.666041
Thermodynamics of Many Black Holes2021-04-22T00:00:00ZRuth GregoryZheng Liang LimAndrew ScoinsWe discuss the thermodynamics of an array of collinear black holes which may be accelerating. We prove a general First Law, including variations in the tensions of strings linking and accelerating the black holes. We analyse the implications of the First Law in a number of instructive cases, including that of the C-metric, and relate our findings to the previously obtained thermodynamics of slowly accelerating black holes in anti-de Sitter spacetime. The concept of thermodynamic length is found to be robust and a Christoudoulou-Ruffini formula for the C-metric is shown.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.628727
https://www.frontiersin.org/articles/10.3389/fphy.2021.628727
Joule-Thomson Expansion of the Quasitopological Black Holes2021-04-19T00:00:00ZBehrouz MirzaFatemeh NaeimipourMasoumeh TavakoliIn this paper, we investigate the thermal stability and Joule-Thomson expansion of some new quasitopological black hole solutions. We first study the higher-dimensional static quasitopological black hole solutions in the presence of Born-Infeld, exponential, and logarithmic nonlinear electrodynamics. The stable regions of these solutions are independent of the types of the nonlinear electrodynamics. The solutions with horizons relating to the positive constant curvature, k=+1, have a larger region in thermal stability, if we choose positive quasitopological coefficients, μi>0. We also review the power Maxwell quasitopological black hole. We then obtain the five-dimensional Yang-Mills quasitopological black hole solution and compare it with the quasitopological Maxwell solution. For large values of the electric charge, q, and the Yang-Mills charge, e, we showed that the stable range of the Maxwell quasitopological black hole is larger than the Yang-Mills one. This is while thermal stability for small charges has the same behavior for these black holes. Thereafter, we obtain the thermodynamic quantities for these solutions and then study the Joule-Thomson expansion. We consider the temperature changes in an isenthalpic process during this expansion. The obtained results show that the inversion curves can divide the isenthalpic ones into two parts in the inversion pressure, Pi. For P<Pi, a cooling phenomenon with positive slope happens in T−P diagram, while there is a heating process with a negative slope for P>Pi. As the values of the nonlinear parameter, β, the electric and Yang-Mills charges decrease, the temperature goes to zero with a small slope and so the heating phenomena happens slowly.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.531766
https://www.frontiersin.org/articles/10.3389/fphy.2021.531766
Renormalization Group Approach to the Continuum Limit of Matrix Models of Quantum Gravity With Preferred Foliation2021-04-16T00:00:00ZAlicia CastroTim Andreas KoslowskiThis contribution is not intended as a review but, by suggestion of the editors, as a glimpse ahead into the realm of dually weighted tensor models for quantum gravity. This class of models allows one to consider a wider class of quantum gravity models, in particular one can formulate state sum models of spacetime with an intrinsic notion of foliation. The simplest one of these models is the one proposed by Benedetti and Henson [1], which is a matrix model formulation of two-dimensional Causal Dynamical Triangulations (CDT). In this paper we apply the Functional Renormalization Group Equation (FRGE) to the Benedetti-Henson model with the purpose of investigating the possible continuum limits of this class of models. Possible continuum limits appear in this FRGE approach as fixed points of the renormalization group flow where the size of the matrix acts as the renormalization scale. Considering very small truncations, we find fixed points that are compatible with analytically known results for CDT in two dimensions. By studying the scheme dependence of our results we find that precision results require larger truncations than the ones considered in the present work. We conclude that our work suggests that the FRGE is a useful exploratory tool for dually weighted matrix models. We thus expect that the FRGE will be a useful exploratory tool for the investigation of dually weighted tensor models for CDT in higher dimensions.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.620430
https://www.frontiersin.org/articles/10.3389/fphy.2020.620430
Fingerprinting the Fractional Order Phase Transitions in AdS Black Holes2021-04-14T00:00:00ZMohamed ChababSamir IraouiIn this paper, we have extended and deepened the study on fractional order phase transition (FPT) of a charged AdS black hole. We have carried out a detailed analysis of FPT for several AdS black hole prototypes: black hole surrounded by quintessence background, 5D Gauss-Bonnet, D dimensional RN-AdS BH, and lastly Kerr black holes. We have shown that the 4/3 order FPT at critical points holds for the first three black holes systems, while for Kerr black holes, the fractional order is rather 1/3. These results suggest two remarkable features: Firstly 4/3 order phase transition can be assumed for asymptotically AdS black holes spherical solutions; secondly the fractional order is not universal and can be affected by the geometric symmetry.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.650421
https://www.frontiersin.org/articles/10.3389/fphy.2021.650421
Experimental Approaches to Neutrino Nuclear Responses for ββ Decays and Astro-Neutrinos2021-04-05T00:00:00ZHiroyasu EjiriFundamental properties of neutrinos are investigated by studying double beta decays (ββ-decays), while atro-neutrino nucleo-syntheses and astro-neutrino productions are investigated by studying inverse beta decays (inverse β-decays) induced by astro-neutrinos. Neutrino nuclear responses for these ββ and β-decays are crucial for these neutrino studies in nuclei. This reports briefly perspectives on experimental studies of neutrino nuclear responses (square of nuclear matrix element) for ββ-decays and astro-neutrinos by using nuclear and leptonic (muon) charge-exchange reactions]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.652536
https://www.frontiersin.org/articles/10.3389/fphy.2021.652536
Comparative Analysis of Nuclear Matrix Elements of 0νβ+β+ Decay and Muon Capture in 106Cd2021-04-01T00:00:00ZLotta JokiniemiJouni SuhonenJenni KotilaComparative analyses of the nuclear matrix elements (NMEs) related to the 0νβ^{+}β^{+} decay of ^{106}Cd to the ground state of ^{106}Pd and the ordinary muon capture (OMC) in ^{106}Cd are performed. This is the first time the OMC NMEs are studied for a nucleus decaying via positron-emitting/electron-capture modes of double beta decay. All the present calculations are based on the proton-neutron quasiparticle random-phase approximation with large no-core single-particle bases and realistic two-nucleon interactions. The effect of the particle-particle interaction parameter g_{pp} of pnQRPA on the NMEs is discussed. In the case of the OMC, the effect of different bound-muon wave functions is studied.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.631471
https://www.frontiersin.org/articles/10.3389/fphy.2021.631471
Thermodynamic Curvature of AdS Black Holes with Dark Energy2021-03-23T00:00:00ZAditya SinghAritra GhoshChandrasekhar BhamidipatiIn this paper, we study the effect of dark energy on the extended thermodynamic structure and interacting microstructures of black holes in AdS, through an analysis of thermodynamic geometry. Considering various limiting cases of the novel equation of state obtained in charged rotating black holes with quintessence, and taking enthalpy H as the key potential in the extended phase space, we scrutinize the behavior of the Ruppeiner curvature scalar R in the entropy-pressure (S,P)-plane (or equivalently in the temperature-volume (T,V)-plane). Analysis of R empirically reveals that dark energy parameterized by α, significantly alters the dominant interactions of neutral, charged and slowly rotating black hole microstructures. In the Schwarzschild-AdS case: black holes smaller than a certain size continue to have attractive interactions whereas larger black holes are completely dominated by repulsive interactions which arise to due dark energy. For charged or rotating AdS black holes with quintessence, R can change sign at multiple points depending upon the relation between α and charge q or angular momentum J. In particular, above a threshold value of α, R is never negative at all, suggesting heuristically that the repulsive interactions due to quintessence are long ranged as opposed to the previously known short ranged repulsion in charged AdS black holes. A mean field interaction potential is proposed whose extrema effectively capture the points where the curvature R changes sign.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.552354
https://www.frontiersin.org/articles/10.3389/fphy.2020.552354
Renormalization of Group Field Theories for Quantum Gravity: New Computations and Some Suggestions2021-02-25T00:00:00ZMarco FinocchiaroDaniele OritiWe discuss motivation and goals of renormalization analyses of group field theory models of simplicial 4d quantum gravity, and review briefly the status of this research area. We present some new computations of perturbative Group field theories amplitudes, concerning in particular their scaling behavior, and the numerical techniques employed to obtain them. Finally, we suggest a number of research directions for further progress.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.551848
https://www.frontiersin.org/articles/10.3389/fphy.2020.551848
Quantum Gravity: A Fluctuating Point of View2021-02-24T00:00:00ZJan M. PawlowskiManuel ReichertIn this contribution, we discuss the asymptotic safety scenario for quantum gravity with a functional renormalization group approach that disentangles dynamical metric fluctuations from the background metric. We review the state of the art in pure gravity and general gravity–matter systems. This includes the discussion of results on the existence and properties of the asymptotically safe ultraviolet fixed point, full ultraviolet-infrared trajectories with classical gravity in the infrared, and the curvature dependence of couplings also in gravity–matter systems. The results in gravity–matter systems concern the ultraviolet stability of the fixed point and the dominance of gravity fluctuations in minimally coupled gravity–matter systems. Furthermore, we discuss important physics properties such as locality of the theory, diffeomorphism invariance, background independence, unitarity, and access to observables, as well as open challenges.]]>https://www.frontiersin.org/articles/10.3389/fphy.2021.612417
https://www.frontiersin.org/articles/10.3389/fphy.2021.612417
Science in Underground Laboratories and DULIA-Bio2021-02-23T00:00:00ZAldo IanniThis paper reports a brief introduction to Deep Underground Laboratories (DULs) and the connection they have with research on biology in extreme environments and the effect of radiation in life. Presently, there are 14 DULs in operation worldwide. Although the main research activity in these infrastructures concerns the search for rare events in astroparticle physics and neutrino physics, DULs offer a unique opportunity to undertake experiments in astrobiology and biology in extreme environments. This is the main motivation of Deep Underground Laboratory Integrated Activity in biology (DULIA-bio) 2019 Workshop, which was held at the Gran Sasso (Italy) underground laboratory. This paper aims to give an introduction to the subject of the Workshop by reviewing the main features of DULs.]]>