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The solutions of many issues, of the ongoing efforts to make deformed graphene a tabletop quantum field theory in curved spacetimes, are presented. A detailed explanation of the special features of curved spacetimes, originating from embedding portions of the Lobachevsky plane into R³, is given, and the special role of coordinates for the physical realizations in graphene is explicitly shown, in general, and for various examples. The Rindler spacetime is reobtained, with new important differences with respect to earlier results. The de Sitter spacetime naturally emerges, for the first time, paving the way to future applications in cosmology. The role of the Bañados, Teitelboim, and Zanelli (BTZ) black hole is also briefly addressed. The singular boundary of the pseudospheres, "Hilbert horizon," is seen to be closely related to the event horizon of the Rindler, de Sitter, and BTZ kind. This gives new, and stronger, arguments for the Hawking phenomenon to take place. An important geometric parameter, c, overlooked in earlier work, takes here its place for physical applications, and it is shown to be related to graphene's lattice spacing, ΙY. It is shown that all surfaces of constant negative curvature, K=-r-2, are unified, in the limit c/r → 0, where they are locally applicable to the Beltrami pseudosphere. This, and c=Ι, allow us (a) to have a phenomenological control on the reaching of the horizon; (b) to use spacetimes different from the Rindler spacetime for the Hawking phenomenon; and (c) to approach the generic surface of the family. An improved expression for the thermal LDOS is obtained. A nonthermal term for the total LDOS is found. It takes into account (i) the peculiarities of the graphene-based Rindler spacetime; (ii) the finiteness of a laboratory surface; and (iii) the optimal use of the Minkowski quantum vacuum, through the choice of this Minkowski-static boundary. [ABSTRACT FROM AUTHOR]

We introduce a CP-violating coupling between the Ricci curvature and the heavy right-handed neutrinos. This splits the Majorana masses of the left- and the right-handed heavy neutrinos. When the heavy neutrinos decay, their decay rates are different into left and right chirality light neutrinos. A time-varying nonzero Ricci curvature can give rise to a net lepton asymmetry. The source of a nonzero curvature in a radiation era is the quantum fluctuations of primordial fields. [ABSTRACT FROM AUTHOR]

In this paper, we study the spin transitions of neutrinos caused by the interaction with a gravitational field. We consider a model with a scalar field (describing screening effects) conformally coupled to matter and neutrinos. The presence of screening effects suppresses the neutrino spin-flip probability as compared with general relativity predictions. Such a result could be used, combined with neutrino astronomy, for testing modified theories of gravity and, in turn, screening effects invoked to bypass the solar system and lab tests. Such an analysis has been also extended to the case of the quintessence field surrounding a black hole. Here we investigate the flavor and spin transitions, showing that also in such a case exists a suppression of the effect compared to general relativity prediction. [ABSTRACT FROM AUTHOR]

We consider dark matter which has nonzero electromagnetic form factors like electric/magnetic dipole moments and anapole moment for fermionic dark matter and Rayleigh form factor for scalar dark matter. We consider dark matter mass mχ>O(MeV) and put constraints on their mass and electromagnetic couplings from cosmic microwave background (CMB) and large scale structure (LSS) observations. Fermionic dark matter with nonzero electromagnetic form factors can annihilate to e+e- and scalar dark matter can annihilate to 2γ at the time of recombination and distort the CMB. We analyze dark matter with multipole moments with Planck and baryon acoustic oscillations (BAO) observations. We find upper bounds on anapole moment gA<7.163×10³ GeV-2, electric dipole moment D<7.978×10-9 e cm, magnetic dipole moment μ<2.959×10-7μB, and the bound on Rayleigh form factor of dark matter is g4/Λ24<1.085×10-2 GeV-2 with 95% C.L. [ABSTRACT FROM AUTHOR]

We investigate the structure of the gravity-induced generalized uncertainty principle in three dimensions. The subtleties of lower-dimensional gravity, and its important differences concerning four and higher dimensions, are duly taken into account, by considering different possible candidates for the gravitational radius, Rg, that is the minimal length/maximal resolution of the quantum mechanical localization process. We find that the event horizon of the M≠0 Bañados-Teitelboim-Zanelli micro-black-hole furnishes the most consistent Rg. This allows us to obtain a suitable formula for the generalized uncertainty principle in three dimensions, and also to estimate the corrections induced by the latter on the Hawking temperature and Bekenstein entropy. We also point to the extremal M=0 case, and its natural unit of length introduced by the cosmological constant, ℓ=1/√-Λ, as a possible alternative to Rg, and present a condensed matter analog realization of this scenario. [ABSTRACT FROM AUTHOR]

In this paper, we present an iterative method to generate an infinite class of new nonlocal field theories whose propagators are ghost-free. We first examine the scalar field case and show that the pole structure of such generalized propagators possesses the standard two derivative pole and in addition can contain complex conjugate poles which, however, do not spoil at least tree level unitarity as the optical theorem is still satisfied. Subsequently, we define analogous propagators for the fermionic sector which is also devoid of unhealthy degrees of freedom. As a third case, we apply the same construction to gravity and define a new set of theories whose graviton propagators around the Minkowski background are ghost-free. Such a wider class also includes nonlocal theories previously studied and Einstein's general relativity as a peculiar limit. Moreover, we compute the linearized gravitational potential generated by a static pointlike source for several gravitational theories belonging to this new class and show that the nonlocal nature of gravity regularizes the singularity at the origin. [ABSTRACT FROM AUTHOR]

In this paper, we propose a wider class of symmetries including the Galilean shift symmetry as a subclass. We will show how to construct ghost-free nonlocal actions, consisting of infinite derivative operators, which are invariant under such symmetries, but whose functional form is not simply given by exponentials of entire functions. Motivated by this, we will consider the case of a scalar field and discuss the pole structure of the propagator which has infinitely many complex conjugate poles, but satisfies the tree-level unitarity. We will also consider the possibility to construct UV complete Galilean theories by showing how the ultraviolet behavior of loop integrals can be ameliorated. Moreover, we will consider kinetic operators respecting the same symmetries in the context of linearized gravity. In such a scenario, the graviton propagator turns out to be ghost free and the spacetime metric generated by a pointlike source is nonsingular. These new nonlocal models can be seen as an infinite derivative generalization of Lee-Wick theories and open a new branch of nonlocal theories. [ABSTRACT FROM AUTHOR]

Investigations on possible violation of Lorentz invariance have been widely pursued in the last decades, both from theoretical and experimental sides. A comprehensive framework to formulate the problem is the standard model extension (SME) proposed by A. Kostelecky, where violation of Lorentz invariance is encoded into specific coefficients. Here we present a procedure to link the deformation parameter β of the generalized uncertainty principle to the SME coefficients of the gravity sector. The idea is to compute the Hawking temperature of a black hole in two different ways. The first way involves the deformation parameter β, and therefore we get a deformed Hawking temperature containing the parameter β. The second way involves a deformed Schwarzschild metric containing the Lorentz violating terms sμν of the gravity sector of the SME. The comparison between the two different techniques yields a relation between β and sμν. In this way bounds on β transferred from sμν are improved by many orders of magnitude when compared with those derived in other gravitational frameworks. Also the opposite possibility of bounds transferred from β to sμν is briefly discussed. [ABSTRACT FROM AUTHOR]

Huge electromagnetic fields are known to be present during the late stages of the dynamics of supernovae. Thus, when dealing with electrodynamics in this context, the possibility may arise to probe nonlinear theories (generalizations of the Maxwellian electromagnetism). We firstly solve Einstein field equations minimally coupled to an arbitrary (current-free) nonlinear Lagrangian of electrodynamics (NLED) in the slow rotation regime a≪M (black hole's mass), up to first order in a/M. We then make use of the robust and self-contained Born-Infeld Lagrangian in order to compare and contrast the physical properties of such NLED spacetime with its Maxwellian counterpart (a slowly rotating Kerr-Newman spacetime), especially focusing on the astrophysics of both neutrino flavor oscillations (νe→νμ, ντ) and spin-flip (νl→νr, "l" stands for "left" and "r" stands for "right", change of neutrino handedness) mass level crossings, the equivalent to gyroscopic precessions. Such analysis proves that in the spacetime of a slowly rotating nonlinear charged black hole (RNCBH), intrinsically associated with the assumption the electromagnetism is nonlinear, the neutrino dynamics in core-collapse supernovae could be significantly changed. In such an astrophysical environment, a positive enhancement (reduction of the electron fraction Ye<0.5) of the r-process may take place. Consequently, it might result in hyperluminous supernova explosions due to enlargement, in atomic number and amount, of the decaying nuclides. Finally, we envisage some physical scenarios that may lead to short-lived charged black holes with high charge-to-mass ratios (associated with unstable highly magnetized neutron stars) and ways to possibly disentangle theories of the electromagnetism from other black hole observables (by means of light polarization measurements). [ABSTRACT FROM AUTHOR]

The first-order phase transitions in the early Universe are one of the well-known sources which release the stochastic background of gravitational waves (GWs). In this paper, we study the contribution of an external static and strong magnetic field on the stochastic background of gravitational waves expected during QCD phase transition. In the light of the strongly magnetized hot QCD equation of state which deviated from the ideal gas up to the one-loop approximation, we estimate two phenomenologically important quantities: peak frequency redshifted to today (fpeak) and GW strain amplitude (h²Ωgw). The trace anomaly induced by the magnetized hot QCD matter around the phase transition generates the stochastic background of GW with peak frequencies lower than the ideal gas-based signal (around nHz). Instead, the strain amplitudes corresponding to the peak frequencies are of the same order of magnitude of the expected signal from ideal gas. This may be promising in the sense that although the strong magnetic field could mask the expected stochastic background of GWs by upgrading the frequency sensitivity of detectors in the future, the magnetized GW is expected to be identified. Faced with the projected reach of detectors EPTA, IPTA, and SKA, we find that for the tail of the magnetized GW signals there remains a mild possibility of detection as it can reach the projected sensitivity of SKA. [ABSTRACT FROM AUTHOR]

In this paper we will show an ultraviolet-infrared connection for ghost-free infinite derivative field theories where the Lagrangians are made up of exponentials of entire functions. In particular, for N-point amplitudes a new scale emerges in the infrared from the ultraviolet, i.e., Meff∼Ms/Nα, where Ms is the fundamental scale beyond the Standard Model and α>0 depends on the specific choice of an entire function and on whether we consider zero or nonzero external momenta. We will illustrate this by first considering a scalar toy model with a cubic interaction and subsequently a scalar toy model inspired by ghost-free infinite derivative theories of gravity. We will briefly discuss some phenomenological implications, such as making the nonlocal region macroscopic in the infrared. [ABSTRACT FROM AUTHOR]

In this paper, we will provide a nonsingular rotating spacetime metric for a ghost-free infinite derivative theory of gravity in a linearized limit. We will provide the predictions for the Lense-Thirring effect for a slowly rotating system, and how it is compared with that from general relativity. [ABSTRACT FROM AUTHOR]

We investigate how pure-state Einstein-Podolsky-Rosen correlations in the internal degrees of freedom of massive particles are affected by a curved spacetime background described by extended theories of gravity. We consider models for which the corrections to the Einstein-Hilbert action are quadratic in the curvature invariants and we focus on the weak-field limit. We quantify nonlocal quantum correlations by means of the violation of the Clauser-Horne-Shimony-Holt inequality, and show how a curved background suppresses the violation by a leading term due to general relativity and a further contribution due to the corrections to Einstein gravity. Our results can be generalized to massless particles such as photon pairs and can thus be suitably exploited to devise precise experimental tests of extended models of gravity. [ABSTRACT FROM AUTHOR]

The vacuum solution of Einstein's theory of general relativity provides a rotating metric with a ring singularity, which is covered by the inner and outer horizons and an ergo region. In this paper, we will discuss how ghost-free, quadratic curvature, infinite derivative gravity (IDG) may resolve the ring singularity. In IDG the nonlocality of the gravitational interaction can smear out the delta-Dirac source distribution by making the metric potential finite everywhere including at r=0. We show that the same feature also holds for a rotating metric. We can resolve the ring singularity such that no horizons are formed in the linear regime by smearing out a delta-source distribution on a ring. We will also show that the Kerr metric does not solve the full nonlinear equations of motion of ghost-free quadratic curvature IDG. [ABSTRACT FROM AUTHOR]