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Andrea Addazi

Publications and source records attributed to Andrea Addazi.

At least 109 records · Page 6Linked to original sources
arXiv2016

Dark Energy and Dark Matter from Yang-Mills Condensate and the Peccei-Quinn mechanism

We analyze a model of cold axion Dark Matter weakly coupled with a dark gluon condensate, reproducing Dark Energy. We first review how to recover the Dark Energy behavior using the functional renormalization group approach, and ground our study on the properties of the effective Lagrangian, to be determined non-perturbatively. Then, within the context of $G_{SM}\times SU(2)_{D}\times U(1)_{PQ}$, we consider YMC interactions with QCD axions. We predict a transfer of Dark Energy density into Dark Matter density in a cosmological time that can be tested in the next generation of experiments dedicated to Dark Energy measures.

gr-qc↗
arXiv2016

Brane Bounce from logarithmic entropic corrections in the bulk

We calculate new corrections to the Brane-world dynamics, lying in a 5D Schwarzschild-De Sitter black hole, generalizing the result of Nojiri, Odintsov and Ogushi (NOO) in Ref.\cite{Nojiri:2002vu}, The NOO entropy effect is based on the Logharitmic correction to the bulk entropy firstly calculated by Mukherji and Pal in Ref.\cite{Mukherji:2002de}. We calculate higher order contributions to the brane worldsheet. The extra terms obtained lead to interesting implications in brane-cosmology. In particular, new entropic terms rapidly disappear in the late Universe while exploding in the very Early Universe. In particular, we show that they may trigger a cosmological bounce in the very early Universe. On the other hand, they contribute to the cosmological expansion in the Late Universe. We also discuss a scenario in which the BLK anisotropies are washed-out, toward a new Ekpyrotic Brane Cosmology.

gr-qc↗
arXiv2016

(Anti)evaporation of Dyonic Black Holes in string-inspired dilaton $f(R)$-gravity

We discuss dyonic black hole solutions in the case of $f(R)$-gravity coupled with a dilaton and two gauge bosons. The study of such a model is highly motivated from string theory. Our Black Hole solutions are extensions of the one firstly studied by Kallosh, Linde, Ortín, Peet and Van Proyen (KLOPV) in [arXiv:hep-th/9205027]. We will show that extreme solutions are unstable. In particular, these solutions have Bousso-Hawking-Nojiri-Odintsov (anti)evaporation instabilities.

gr-qc↗
arXiv2016

String completion of an $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ electroweak model

The extended electroweak $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ symmetry framework "explaining" the number of fermion families is revisited. While $331$-based schemes can not easily be unified within the conventional field theory sense, we show how to do it within an approach based on D-branes and (un)oriented open strings, on Calabi-Yau singularities. We show how the theory can be UV-completed in a quiver setup, free of gauge and string anomalies. Lepton and baryon numbers are perturbatively conserved, so neutrinos are Dirac-type, and their lightness results from a novel TeV scale seesaw mechanism. Dynamical violation of baryon number by exotic instantons could induce neutron-antineutron oscillations, with proton decay and other dangerous R-parity violating processes strictly forbidden.

hep-ph↗
arXiv2016

Way-out to the Gravitino problem in intersecting D-brane Pati-Salam models

We discuss the gravitino problem in contest of the Exotic see-saw mechanism for neutrinos and Leptogenesis, UV completed by intersecting D-branes Pati-Salam models. In the Exotic see-saw model, supersymmetry is broken at high scales $M_{SUSY}>10^{9}\, \rm GeV$ and this seems in contradiction with gravitino bounds from inflation and baryogenesis. However, if gravitino is the Lightest Stable Supersymmetric Particle, it will not decay into other SUSY particles, avoiding the gravitino problem and providing a good Cold Dark Matter. Gravitini are Super Heavy Dark Particles and they can be produced by non-adiabatic expansion during inflation. Intriguingly, from bounds on the correct abundance of dark matter, we also constrain the neutrino sector. We set a limit on the exotic instantonic coupling of $<10^{-2}÷10^{-3}$. This also sets important constrains on the Calabi-Yau compactifications and on the string scale. This model strongly motivates very high energy DM indirect detection of neutrini and photons of $10^{11}÷10^{13}\, \rm GeV$: gravitini can decay on them in a cosmological time because of soft R-parity breaking effective operators.

hep-ph↗
arXiv2016

$\infty-\infty$: vacuum energy and virtual black-holes

We discuss other contributions to the vacuum energy of quantum field theories and quantum gravity, which have not been considered in literature. As is well known, the presence of virtual particles in vacuum provides the so famous and puzzling contributions to the vacuum energy. As is well known, these mainly come from loop integrations over the four-momenta space. However, we argue that these also imply the presence of a mass density of virtual particles in every volume cell of space-time. The most important contribution comes from quantum gravity $S^{2}\times S^{2}$ bubbles, corresponding to virtual black hole pairs. The presence of virtual masses could lead to another paradox: the space-time itself would have an intrinsic virtual mass density contribution leading to a disastrous contraction - as is known, no negative masses exist in general relativity. We dub this effect {\it the cosmological problem of second type}: if not other counter-terms existed, the vacuum energy would be inevitably destabilized by virtual-mass contributions. It would be conceivable that the cosmological problem of second type could solve the first one. Virtual masses renormalize the vacuum energy to an unpredicted parameter, as in the renormalization procedure of the Standard Model charges. In the limit of $M_{Pl}\rightarrow \infty$ (Pauli-Villars limit), virtual black holes have a mass density providing an infinite counter-term to the vacuum energy divergent contribution $M_{Pl} \rightarrow \infty$ (assuming $M_{UV}=M_{Pl}$). Therefore, in the same Schwinger-Feynman-Tomonaga attitude, the problem of a divergent vacuum energy could be analogous to the {\it put-by-hand} procedure used for Standard Model parameters.

hep-th↗
arXiv2016

Chaotic instantons in scalar field theory

We consider a new class of instantons in context of quantum field theory of a scalar field coupled with a chaotic background source field. We show how the instanton associated to the quantum tunneling from a metastable false to the true vacuum will be corrected by an exponential enhancement factor. Possible implications are discussed.

hep-th↗
arXiv2016

Born-Infeld condensate as a possible origin of neutrino masses and dark energy

We discuss the possibility that a Born-Infeld condensate coupled to neutrinos can generate both neutrino masses and an effective cosmological constant. In particular, an effective field theory is provided capable of dynamically realizing the neutrino superfluid phase firstly suggested by Ginzburg and Zharkov. In such a case, neutrinos acquire a mass gap inside the Born-Infeld ether forming a long-range Cooper pair. Phenomenological implications of the approach are also discussed.

gr-qc↗
arXiv2016

Weak Gravity Conjecture as a Razor Criterium for Exotic D-brane instantons

We discuss implications of Weak gravity conjecture (WGC) for exotic D-brane instantons. In particular, WGC leads to indirect stringent bounds on non-perturbative superpotentials generated by exotic instantons, with many implications for phenomenology: R-parity violating processes, neutrino mass, $μ$-problem, Neutron-Antineutron transitions and collider physics.

hep-th↗
arXiv2016

Gauged B-L Number and Neutron--Antineutron Oscillation: Long-range Forces Mediated by Baryophotons

Transformation of neutron to antineutron is a small effect that has not yet been experimentally observed. %\cite{Phillips:2014fgb}. In principle, it can occur with free neutrons in the vacuum or with bound neutrons inside the nuclear environment different for neutrons and antineutrons and for that reason in the latter case it is heavily suppressed. Free neutron transformation also can be suppressed if environmental vector field exists destinguishing neutron from antineutron. We consider here the case of a vector field coupled to $B-L$ charge of the particles ($B-L$ photons) and study a possibility of this to lead to the observable suppression of neutron to antineutron transformation. The suppression effect however can be removed by applying external magnetic field. If the neutron--antineutron oscillation will be discovered in free neutron oscillation experiments, this will imply limits on $B-L$ photon coupling constant and interaction radius few order of magnitudes stronger than present limits form the tests of the equivalence principle. If $n-\bar n$ oscillation will be discovered via nuclear instability, but not in free neutron oscillations in corresponding level, this would indicate to the presence of fifth-forces mediated by such baryophotons.

hep-ph↗
arXiv2016

More about Neutron Majorana mass from Exotic Instantons: an alternative mechanism in Low-Scale String theory

We discuss an alternative for Baryon-violating six quarks transitions, in the contest of low scale string theory. In particular, with $M_{S}=10÷10^{3}\rm TeV$, such a transition can be mediated by two color-triplets,through a quartic coupling with down-quarks,generated by exotic instantons, in a calculable and controllable way. We show how FCNCs limits on color-triplet massare well compatible with $n-\bar{n}$ oscillation ones. If a $n-\bar{n}$ transition were found, this would be an indirect hint for our model. This would strongly motivate researches of direct channels in proton-proton colliders. In fact, our model can be directly tested in a experimentally challenging $100÷1000\, \rm TeV$ proton-proton collider, searching for our desired color-triplet states and an evidence for exotic instantons resonances, in addition to stringy Regge resonances, anomalous $Z'$-bosons and gauged megaxion. In particular, our scenario can be related to the $750\, \rm GeV$ diphoton hint identifying it with the gauged megaxion dual to the $B$-field. On the other hand, this scenario is compatible with TeV-ish color triplets visible at LHC and with $1÷10\, \rm TeV$- string scale, {\it i.e} stringy resonances at LHC.

hep-ph↗
arXiv2016

Dynamical R-parity violations from exotic instantons

We show how R-parity can be dynamically broken by non-perturbative quantum gravity effects. In particular, in D-brane models, Exotic instantons provide a simple and calculable mechanism for the generation of R-parity violating bilinear, trilinear and higher order superpotential terms. We show examples of MSSM-like D-brane models, in which one Exotic Instanton induces only one term among the possible R-parity violating superpotentials. Naturally, the idea can be generalized for other gauge groups. As a consequence, a dynamical violation of R-parity does not necessarily destabilize the proton, i.e. a strong fine tuning is naturally avoided, in our case. For example, a Lepton violating superpotential term can be generated without generating Baryon violating terms, and viceversa. This has strong implications in phenomenology: neutrino, neutron-antineutron, electric dipole moments, dark matter and LHC physics.

hep-ph↗
arXiv2016

Direct generation of a Majorana mass for the Neutron from Exotic Instantons

We discuss a new mechanism in which non-perturbative quantum gravity effects directly generate a Majorana mass for the neutron. In particular, in string theory, exotic instantons can generate an effective six quark operator by calculable mixed disk amplitudes. In a low string scale scenario, with $M_{S}\simeq 10÷10^{5}\, \rm TeV$, a neutron-antineutron oscillation can be reached in the next generation of experiments. we argue that protons and neutralinos are not destabilized and that dangerous FCNCs are not generated. We show an example of quiver theories, locally free by tadpoles and anomalies, reproducing MSSM plus a Majorana neutron and a Majorana neutrino. These models naturally provide a viable baryogenesis mechanism by resonant RH neutrino decays, as well as a stable WIMP-like dark matter. We also discuss how LHC data will provide useful inputs for our model, in the immediate future, testing several different regions of the parameter space. Such a mechanism represents a simple and calculable counter-example to the Wilsonian UV completion of effective non-renormalizable operators.

hep-ph↗
arXiv2016

Quantum chaos inside space-temporal Sinai billiards

We discuss general aspects of non-relativistic quantum chaos theory of scattering of a quantum particle on a system of a large number of naked singularities. We define such a system space-temporal Sinai billiard We dis- cuss the problem in semiclassical approach. We show that in semiclassical regime the formation of trapped periodic semiclassical orbits inside the sys- tem is unavoidable. This leads to general expression of survival probabilities and scattering time delays, expanded to the chaotic Pollicott-Ruelle reso- nances. Finally, we comment on possible generalizations of these aspects to relativistic quantum field theory.

gr-qc↗
arXiv2016

A Unified picture of Dark Matter and Dark Energy from Invisible QCD

It has been shown in a companion paper that the late time acceleration of the universe can be accounted for by an extension of the QCD color to a $SU(3)$ invisible sector (IQCD). In this work we discuss a unified framework such the scale of dark chiral-breaking dictates both the accelerated expansion of the universe, and the origin of dark matter. We find that the strong and gravitational dynamics of dark quarks and gluons evolve to eventually form exotic dark stars. We discuss the dynamical complexity of these dark compact objects in light of dark big bang nucleosynthesis. We argue how IQCD favors a halo composed of very compact dark neutron stars, strange/quark stars and black holes, with masses $M_{MACHO}< 10^{-7}M_{\odot}$. This avoids limit from MACHO and EROS collaborations as well as limit from clusters. We also discuss possible phenomenological implications in dark matter searches. We argue that dark supernovae and dark binaries can emit very peculiar gravitational waves signal testable by the LIGO/VIRGO collaboration and future projects dedicated to these aspects.

gr-qc↗
arXiv2016

Chaotization inside Quantum Black Holes

We show how the horizon geometry and entropy of a Semiclassical Black Hole can be reconstructed from a system of $N>>1$ horizonless conic singularities with average opening angle at the horizon $\langle Θ\rangle=2π$. This conclusion is strongly motivated by a generalized Wheeler-De Witt equation for quantum black holes. We will argument how infalling information will be inevitably chaotized in these systems. A part of the initial probability density will be trapped inside the system, in back and forth scatterings among conic singularities, for a characteristic time close to the Semiclassical BH life-time. Further implications on information paradoxes are discussed.

gr-qc↗
arXiv2016

Exotic see-saw mechanism for neutrinos and leptogenesis in a Pati-Salam model

We discuss non-perturbative corrections to the neutrino sector, in the context of a D-brane Pati-Salam-like model, that can be obtained as a simple alternative to $SO(10)$ GUT's in theories with open and unoriented strings. In such D-brane models, exotic stringy instantons can correct the right-handed neutrino mass matrix in a calculable way, thus affecting mass hierarchies and modifying the see-saw mechanism to what we name exotic see-saw. For a wide range of parameters, a compact spectrum of right-handed neutrino masses can occur that gives rise to a predictive scenario for low energy observables. This model also provides a viable mechanism for Baryon Asymmetry in the Universe (BAU) through leptogenesis. Finally, a Majorana mass for the neutron is naturally predicted in the model, leading to potentially testable neutron-antineutron oscillations. Combined measurements in neutrino and neutron-antineutron sectors could provide precious informations on physics at the quantum gravity scale.

hep-ph↗