Search results for "460"
showing 10 items of 197 documents
Mapping nonlinear gravity into General Relativity with nonlinear electrodynamics
2018
We show that families of nonlinear gravity theories formulated in a metric-affine approach and coupled to a nonlinear theory of electrodynamics can be mapped into General Relativity (GR) coupled to another nonlinear theory of electrodynamics. This allows to generate solutions of the former from those of the latter using purely algebraic transformations. This correspondence is explicitly illustrated with the Eddington-inspired Born-Infeld theory of gravity, for which we consider a family of nonlinear electrodynamics and show that, under the map, preserve their algebraic structure. For the particular case of Maxwell electrodynamics coupled to Born-Infeld gravity we find, via this corresponden…
Non-quadratic improved Hessian PDF reweighting and application to CMS dijet measurements at 5.02 TeV
2019
Hessian PDF reweighting, or "profiling", has become a widely used way to study the impact of a new data set on parton distribution functions (PDFs) with Hessian error sets. The available implementations of this method have resorted to a perfectly quadratic approximation of the initial $\chi^2$ function before inclusion of the new data. We demonstrate how one can take into account the first non-quadratic components of the original fit in the reweighting, provided that the necessary information is available. We then apply this method to the CMS measurement of dijet pseudorapidity spectra in proton-proton (pp) and proton-lead (pPb) collisions at 5.02 TeV. The measured pp dijet spectra disagree…
Can we fit nuclear PDFs with the high-x CLAS data?
2020
AbstractNuclear parton distribution functions (nuclear PDFs) are non-perturbative objects that encode the partonic behaviour of bound nucleons. To avoid potential higher-twist contributions, the data probing the high-x end of nuclear PDFs are sometimes left out from the global extractions despite their potential to constrain the fit parameters. In the present work we focus on the kinematic corner covered by the new high-x data measured by the CLAS/JLab collaboration. By using the Hessian re-weighting technique, we are able to quantitatively test the compatibility of these data with globally analyzed nuclear PDFs and explore the expected impact on the valence-quark distributions at high x. W…
Looking at the axionic dark sector with ANITA
2020
The ANITA experiment has recently observed two anomalous events emerging from well below the horizon. Even though they are consistent with tau cascades, a high energy Standard Model or Beyond the Standard Model explanation is challenging and in tension with other experiments. We study under which conditions the reflection of generic radio pulses can reproduce these signals. We propose that these pulses can be resonantly produced in the ionosphere via axion-photon conversion. This naturally explains the direction and polarization of the events and avoids other experimental bounds.
Entropy Production during Asymptotically Safe Inflation
2011
The Asymptotic Safety scenario predicts that the deep ultraviolet of Quantum Einstein Gravity is governed by a nontrivial renormalization group fixed point. Analyzing its implications for cosmology using renormalization group improved Einstein equations we find that it can give rise to a phase of inflationary expansion in the early Universe. Inflation is a pure quantum effect here and requires no inflaton field. It is driven by the cosmological constant and ends automatically when the renormalization group evolution has reduced the vacuum energy to the level of the matter energy density. The quantum gravity effects also provide a natural mechanism for the generation of entropy. It could eas…
f(R) constant-roll inflation
2017
The previously introduced class of two-parametric phenomenological inflationary models in General Relativity in which the slow-roll assumption is replaced by the more general, constant-roll condition is generalized to the case of $f(R)$ gravity. A simple constant-roll condition is defined in the original Jordan frame, and exact expressions for a scalaron potential in the Einstein frame, for a function $f(R)$ (in the parametric form) and for inflationary dynamics are obtained. The region of the model parameters permitted by the latest observational constraints on the scalar spectral index and the tensor-to-scalar ratio of primordial metric perturbations generated during inflation is determin…
Effective interactions in Ricci-Based Gravity below the non-metricity scale
2020
We show how minimally-coupled matter fields of arbitrary spin, when coupled to Ricci-Based Gravity theories, develop non-trivial effective interactions that can be treated perturbatively only below a characteristic high-energy scale $\Lambda_Q$. Our results generalize to arbitrary matter fields those recently obtained for spin 1/2 fields in \cite{Latorre:2017uve}. We then use this interactions to set bounds on the high-energy scale $\Lambda_Q$ that controls departures of Ricci-Based Gravity theories from General Relativity. Particularly, for Eddington-inspired Born-Infeld gravity we obtain the strong bound $ |\kappa|<3.5 \times 10^{-14} \text{ m}^5 \text{kg}^{-1}\text{s}^{-2} $.
DsixTools 2.0: The Effective Field Theory Toolkit
2021
$\tt DsixTools$ is a Mathematica package for the handling of the Standard Model Effective Field Theory (SMEFT) and the Low-energy Effective Field Theory (LEFT) with operators up to dimension six, both at the algebraic and numerical level. $\tt DsixTools$ contains a visually accessible and operationally convenient repository of all operators and parameters of the SMEFT and the LEFT. This repository also provides information concerning symmetry categories and number of degrees of freedom, and routines that allow to implement this information on global expressions (such as decay amplitudes and cross-sections). $\tt DsixTools$ also performs weak basis transformations, and implements the full on…
Neutrino pair annihilation ( $$\nu {\bar{\nu }}\rightarrow e^-e^+$$ ν ν ¯ → e - e + ) in the presence of quintessence surrounding a black hole
2021
Quintessence fields, introduced to explain the speed-up of the Universe, might affect the geometry of spacetime surrounding black holes, as compared to the standard Schwarzschild and Kerr geometries. In this framework, we study the neutrino pairs annihilation into electron-positron pairs ($\nu{\bar \nu}\to e^-e^+$) near the surface of a neutron star, focusing, in particular, on the Schwarzschild-like geometry in presence of quintessence fields. The effect of the latter is to increase the minimum photon-sphere radius ($R_{ph}$), increasing in such a way the maximum energy deposition rate near to $R_{ph}$. The rate turns out to be several orders of magnitude greater than the rate computed in …
Sterile Neutrinos, Black Hole Vacuum and Holographic Principle
2021
We construct an effective field theory (EFT) model that describes matter field interactions with Schwarzschild mini-black-holes (SBH's), treated as a scalar field, $B_0(x)$. Fermion interactions with SBH's require a random complex spurion field, $\theta_{ij}$, which we interpret as the EFT description of "holographic information," which is correlated with the SBH as a composite system. We consider Hawking's virtual black hole vacuum (VBH) as a Higgs phase, $\langle B_0 \rangle =V$. Integrating sterile neutrino loops, the field $\theta_{ij}$ is promoted to a dynamical field, necessarily developing a tachyonic instability and acquiring a VEV of order the Planck scale. For $N$ sterile neutrino…