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Sep 21, 2013
09/13
by
Giulia Gubitosi; Flavio Mercati
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We show that the $\kappa$-Poincar\'e Hopf algebra can be interpreted in the framework of curved momentum space leading to the relativity of locality \cite{AFKS}. We study the geometric properties of the momentum space described by $\kappa$-Poincar\'e, and derive the consequences for particles propagation and energy-momentum conservation laws in interaction vertices, obtaining for the first time a coherent and fully workable model of the deformed relativistic kinematics implied by...
Source: http://arxiv.org/abs/1106.5710v2
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4.0
Jun 29, 2018
06/18
by
Giulia Gubitosi; Joao Magueijo
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eye 4
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We examine some of the roots of parity violation for gravitons and uncover a closely related new effect: correlations between right and left handed gravitons. Such correlators have spin 4 if they involve gravitons moving along the same direction, and spin zero for gravitons moving with opposite directions. In the first case, the most immediate implication would be a degree of linear polarization for the tensor vacuum fluctuations, which could be seen by gravity wave detectors sensitive enough...
Topics: Astrophysics, Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1610.05702
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60
Sep 18, 2013
09/13
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Giulia Gubitosi; Francesco Paci
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eye 60
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We study the possibility of constraining the energy dependence of cosmological birefringence by using CMB polarization data. We consider four possible behaviors, characteristic of different theoretical scenarios: energy-independent birefringence motivated by Chern-Simons interactions of the electromagnetic field, linear energy dependence motivated by a 'Weyl' interaction of the electromagnetic field, quadratic energy dependence, motivated by quantum gravity modifications of low-energy...
Source: http://arxiv.org/abs/1211.3321v2
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3.0
Jun 28, 2018
06/18
by
Giulia Gubitosi; Joao Magueijo
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We revisit one of the earliest proposals for deformed dispersion relations in the light of recent results on dynamical dimensional reduction and production of cosmological fluctuations. Depending on the specification of the measure of integration and addition rule in momentum space the model may be completed so as to merely deform Lorentz invariance, or so as to introduce a preferred frame. Models which violate Lorentz invariance have a negative UV asymptotic dimension and a very red spectrum...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1512.03268
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4.0
Jun 28, 2018
06/18
by
Leonardo Barcaroli; Giulia Gubitosi
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We present the first detailed study of the kinematics of free relativistic particles whose symmetries are described by a quantum deformation of the de Sitter algebra, known as $q$-de Sitter Hopf algebra. The quantum deformation parameter is a function of the Planck length $\ell$ and the de Sitter radius $H^{-1}$, such that when the Planck length vanishes, the algebra reduces to the de Sitter algebra, while when the de Sitter radius is sent to infinity one recovers the $\kappa$-Poincar\'e Hopf...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1512.03462
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41
Sep 21, 2013
09/13
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Giulia Gubitosi; Eric V. Linder
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Cosmic acceleration can be achieved not only with a sufficiently flat scalar field potential but through kinetic terms coupled to gravity. These derivative couplings impose a shift symmetry on the scalar field, aiding naturalness. We write the most general purely kinetic action not exceeding mass dimension six and obeying second order field equations. The result reduces to a simple form involving a coupling of the Einstein tensor with the kinetic term and can be interpreted as adding a new term...
Source: http://arxiv.org/abs/1106.2815v1
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5.0
Jun 28, 2018
06/18
by
Giulia Gubitosi; Michele Arzano; Joao Magueijo
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We show that the two-point function of a quantum field theory with de Sitter momentum space (herein called DSR) can be expressed as the product of a standard delta function and an energy-dependent factor. This is a highly non-trivial technical result in any theory without a preferred frame. Applied to models exhibiting running of the dimensionality of space, this result is essential in proving that vacuum fluctuations are generally scale-invariant at high energies whenever there is running to...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1511.03191
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63
Sep 22, 2013
09/13
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Giulia Gubitosi; Federico Piazza; Filippo Vernizzi
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We propose a universal description of dark energy and modified gravity that includes all single-field models. By extending a formalism previously applied to inflation, we consider the metric universally coupled to matter fields and we write in terms of it the most general unitary gauge action consistent with the residual unbroken symmetries of spatial diffeomorphisms. Our action is particularly suited for cosmological perturbation theory: the background evolution depends on only three...
Source: http://arxiv.org/abs/1210.0201v2
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3.0
Jun 29, 2018
06/18
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Francesco Brighenti; Giulia Gubitosi; Joao Magueijo
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We compute the spectral index of primordial perturbations in a rainbow universe. We allow the Newton constant $G$ to run at (super-)Planckian energies and we consider both vacuum and thermal perturbations. If the rainbow metric is the one associated to a generalized Horava-Lifshitz dispersion relation, we find that only when $G$ tends asymptotically to zero can one match the observed value of the spectral index and solve the horizon problem, both for vacuum and thermal perturbations. For vacuum...
Topics: High Energy Physics - Theory, Astrophysics, Cosmology and Nongalactic Astrophysics, General...
Source: http://arxiv.org/abs/1612.06378
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4.0
Jun 30, 2018
06/18
by
Giulia Gubitosi; Matteo Martinelli; Luca Pagano
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We introduce birefringence effects within the propagation history of CMB, considering the two cases of a constant effect and of an effect that increases linearly in time, as the rotation of polarization induced by birefringence accumulates during photon propagation. Both cases result into a mixing of E and B modes before lensing effects take place, thus leading to the fact that lensing is acting on spectra that are already mixed because of birefringence. Moreover, if the polarization rotation...
Topics: Astrophysics, Cosmology and Nongalactic Astrophysics
Source: http://arxiv.org/abs/1410.1799
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55
Sep 22, 2013
09/13
by
Giovanni Amelino-Camelia; Giulia Gubitosi; Flavio Mercati
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We introduce an area operator for the Moyal noncommutative plane. We find that the spectrum is discrete, but, contrary to the expectation formulated by other authors, not characterized by a "minimum-area principle". We show that an intuitive analysis of the uncertainty relations obtained from Moyal-plane noncommutativity is fully consistent with our results for the spectrum, and we argue that our area operator should be generalizable to several other noncommutative spaces. We also...
Source: http://arxiv.org/abs/0812.3663v2
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Sep 22, 2013
09/13
by
Giovanni Amelino-Camelia; Giulia Gubitosi; Flavio Mercati
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Motivation for the study of spacetime noncommutativity comes primarily from its possible use in investigations of (Planck-scale) spacetime fuzziness, but most work focuses on S-matrix/field-theory observables and still very little has been established for geometric observables. We argue that it might be useful to exploit the "pregeometric" formulation of spacetime noncommutativity, which in particular describes the coordinates of the Moyal plane in terms of the phase-space coordinates...
Source: http://arxiv.org/abs/0812.2675v2
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19
Jun 26, 2018
06/18
by
Grasiele Santos; Giulia Gubitosi; Giovanni Amelino-Camelia
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It has been recently claimed that the initial singularity might be avoided in the context of rainbow cosmology, where one attempts to account for quantum-gravitational corrections through an effective-theory description based on an energy-dependent ("rainbow") space-time metric. We here scrutinize this exciting hypothesis much more in depth than previous analyses. In particular, we take into account all requirements for singularity avoidance, while previously only a subset of these...
Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1502.02833
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21
Jun 28, 2018
06/18
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Giulia Gubitosi; Macarena Lagos; Joao Magueijo; Rupert Allison
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In this paper we consider the issue of paradigm evaluation by applying Bayes' theorem along the following nested hierarchy of progressively more complex structures: i) parameter estimation (within a model), ii) model selection and comparison (within a paradigm), iii) paradigm evaluation. In such a hierarchy the Bayesian evidence works both as the posterior's normalization at a given level and as the likelihood function at the next level up. Whilst raising no objections to the standard...
Topics: High Energy Physics - Phenomenology, Cosmology and Nongalactic Astrophysics, Astrophysics, General...
Source: http://arxiv.org/abs/1506.09143
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Sep 19, 2013
09/13
by
Giovanni Amelino-Camelia; Giulia Gubitosi; Flavio Mercati; Giacomo Rosati
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The recently-developed techniques of Noether analysis of the quantum-group spacetime symmetries of some noncommutative field theories rely on the {\it ad hoc} introduction of some peculiar auxiliary transformation parameters, which appear to have no role in the structure of the quantum group. We here show that it is possible to set up the Noether analysis directly in terms of the quantum-group symmetry transformations, and we therefore establish more robustly the attribution of the conserved...
Source: http://arxiv.org/abs/1009.3264v1
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11
Jun 27, 2018
06/18
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Giovanni Amelino-Camelia; Michele Arzano; Giulia Gubitosi; Joao Magueijo
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eye 11
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We propose that at the beginning of the universe gravity existed in a limbo either because it was switched off or because it was only conformally coupled to all particles. This picture can be reverse-engineered from the requirement that the cosmological perturbations be (nearly) scale-invariant without the need for inflation. It also finds support in recent results in quantum gravity suggesting that spacetime becomes two-dimensional at super-Planckian energies. We advocate a novel top-down...
Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory
Source: http://arxiv.org/abs/1505.04649
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4.0
Jun 30, 2018
06/18
by
Michele Arzano; Giulia Gubitosi; Joao Magueijo; Giovanni Amelino-Camelia
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eye 4
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We investigate the anti-de Sitter (AdS) counterpart to the well studied de Sitter (dS) model for energy-momentum space, viz "$\kappa$-momentum space" space (with a structure based on the properties of the $\kappa$-Poincar\'e Hopf algebra). On the basis of previous preliminary results one might expect the two models to be "dual": dS exhibiting an invariant maximal spatial momentum but unbounded energy, AdS a maximal energy but unbounded momentum. If that were the case AdS...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1412.2054
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10.0
Jun 27, 2018
06/18
by
Michele Arzano; Giulia Gubitosi; Joao Magueijo; Giovanni Amelino-Camelia
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eye 10
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We examine vacuum fluctuations in theories with modified dispersion relations which represent dimensional reduction at high energies. By changing units of energy and momentum we can obtain a description rendering the dispersion relations undeformed and transferring all the non-trivial effects to the integration measure in momentum space. Using this description we propose a general quantization procedure, which should be applicable whether or not the theory explicitly introduces a preferred...
Topics: High Energy Physics - Phenomenology, General Relativity and Quantum Cosmology, Cosmology and...
Source: http://arxiv.org/abs/1505.05021
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6.0
Jun 30, 2018
06/18
by
Philippe Brax; Clare Burrage; Anne-Christine Davis; Giulia Gubitosi
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We investigate the cosmological properties of Galileon models with positive kinetic terms. We include both conformal and disformal couplings to matter and focus on constraints on the theory that arise because of these couplings. The disformal coupling to baryonic matter is extremely constrained by astrophysical and particle physics effects. The disformal coupling to photons induces a cosmological variation of the speed of light and therefore distortions of the Cosmic Microwave Background...
Topics: High Energy Physics - Phenomenology, Astrophysics, Cosmology and Nongalactic Astrophysics
Source: http://arxiv.org/abs/1411.7621
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55
Sep 17, 2013
09/13
by
Giulia Gubitosi; Giuseppe Genovese; Giovanni Amelino-Camelia; Alessandro Melchiorri
texts
eye 55
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In the study of Planck-scale ("quantum-gravity induced") violations of Lorentz symmetry, an important role was played by the deformed-electrodynamics model introduced by Myers and Pospelov. Its reliance on conventional effective quantum field theory, and its description of symmetry-violation effects simply in terms of a four-vector with nonzero component only in the time-direction, rendered it an ideal target for experimentalists and a natural concept-testing ground for many...
Source: http://arxiv.org/abs/1003.0878v1
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4.0
Jun 29, 2018
06/18
by
Giovanni Amelino-Camelia; Francesco Brighenti; Giulia Gubitosi; Grasiele Santos
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eye 4
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Recent results suggest that a crucial crossroad for quantum gravity is the characterization of the effective dimension of spacetime at short distances, where quantum properties of spacetime become significant. This is relevant in particular for various scenarios of "dynamical dimensional reduction" which have been discussed in the literature. We are here concerned with the fact that the related research effort has been based mostly on analyses of the "spectral dimension",...
Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1602.08020
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4.0
Jun 30, 2018
06/18
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Leonardo Barcaroli; Lukas K. Brunkhorst; Giulia Gubitosi; Niccoló Loret; Christian Pfeifer
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We use our previously developed identification of dispersion relations with Hamilton functions on phase space to locally implement the $\kappa$-Poincar\'e dispersion relation in the momentum spaces at each point of a generic curved spacetime. We use this general construction to build the most general Hamiltonian compatible with spherical symmetry and the Plank-scale-deformed one such that in the local frame it reproduces the $\kappa$-Poincar\'e dispersion relation. Specializing to...
Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory
Source: http://arxiv.org/abs/1703.02058
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Jun 28, 2018
06/18
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Leonardo Barcaroli; Lukas K. Brunkhorst; Giulia Gubitosi; Niccoló Loret; Christian Pfeifer
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eye 16
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We describe the Hamilton geometry of the phase space of particles whose motion is characterised by general dispersion relations. In this framework spacetime and momentum space are naturally curved and intertwined, allowing for a simultaneous description of both spacetime curvature and non-trivial momentum space geometry. We consider as explicit examples two models for Planck-scale modified dispersion relations, inspired from the $q$-de Sitter and $\kappa$-Poincar\'e quantum groups. In the first...
Topics: General Relativity and Quantum Cosmology, High Energy Physics - Theory
Source: http://arxiv.org/abs/1507.00922
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3.0
Jun 29, 2018
06/18
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Leonardo Barcaroli; Lukas K. Brunkhorst; Giulia Gubitosi; Niccoló Loret; Christian Pfeifer
texts
eye 3
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The covariant understanding of dispersion relations as level sets of Hamilton functions on phase space enables us to derive the most general dispersion relation compatible with homogeneous and isotropic spacetimes. We use this concept to present a Planck-scale deformation of the Hamiltonian of a particle in Friedman-Lema\^itre-Robertson-Walker (FLRW) geometry that is locally identical to the $\kappa$-Poincar\'e dispersion relation, in the same way as the dispersion relation of point particles...
Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1612.01390
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6.0
Jun 30, 2018
06/18
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Giovanni Amelino-Camelia; Leonardo Barcaroli; Giulia Gubitosi; Stefano Liberati; Niccoló Loret
texts
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Finsler geometry is a well known generalization of Riemannian geometry which allows to account for a possibly non trivial structure of the space of configurations of relativistic particles. We here establish a link between Finsler geometry and the sort of models with curved momentum space and DSR-relativistic symmetries which have been recently of interest in the quantum-gravity literature. We use as case study the much-studied scenario which is inspired by the $\kappa$-Poincar\'e quantum...
Topics: High Energy Physics - Theory, General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1407.8143
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60
Sep 18, 2013
09/13
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Giovanni Amelino-Camelia; Giulia Gubitosi; Antonino Marcianó; Pierre Martinetti; Flavio Mercati
texts
eye 60
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We study boost and space-rotation transformations in kappa-Minkowski noncommutative spacetime, using the techniques that some of us had previously developed (hep-th/0607221) for a description of translations in kappa-Minkowski, which in particular led to the introduction of translation transformation parameters that do not commute with the spacetime coordinates. We find a similar description of boosts and space rotations, which allows us to identify some associated conserved charges, but the...
Source: http://arxiv.org/abs/0707.1863v1
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55
Sep 23, 2013
09/13
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Giulia Gubitosi; Luca Pagano; Giovanni Amelino-Camelia; Alessandro Melchiorri; Asantha Cooray
texts
eye 55
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We show that the Cosmic Microwave Background (CMB) polarization data gathered by the BOOMERanG 2003 flight and WMAP provide an opportunity to investigate {\it in-vacuo} birefringence, of a type expected in some quantum pictures of space-time, with a sensitivity that extends even beyond the desired Planck-scale energy. In order to render this constraint more transparent we rely on a well studied phenomenological model of quantum-gravity-induced birefringence, in which one easily establishes that...
Source: http://arxiv.org/abs/0904.3201v1
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57
Sep 23, 2013
09/13
by
Giovanni Amelino-Camelia; Giulia Gubitosi; Niccoló Loret; Flavio Mercati; Giacomo Rosati
texts
eye 57
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The reference laboratory bounds on superluminality of the electron are obtained from the absence of in-vacuo Cherenkov processes and the determinations of synchrotron radiated power for LEP electrons. It is usually assumed that these analyses establish the validity of a standard special-relativistic description of the electron with accuracy of at least a few parts in $10^{14}$, and in particular this is used to exclude electron superluminality with such an accuracy. We observe that these bounds...
Source: http://arxiv.org/abs/1111.0993v1
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55
Sep 21, 2013
09/13
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Giovanni Amelino-Camelia; Fabio Briscese; Giulia Gubitosi; Antonino Marciano; Pierre Martinetti; Flavio Mercati
texts
eye 55
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We study the twisted-Hopf-algebra symmetries of observer-independent canonical spacetime noncommutativity, for which the commutators of the spacetime coordinates take the form [x^{mu},x^{nu}]=i theta^{mu nu} with observer-independent (and coordinate-independent) theta^{mu nu}. We find that it is necessary to introduce nontrivial commutators between transformation parameters and spacetime coordinates, and that the form of these commutators implies that all symmetry transformations must include a...
Source: http://arxiv.org/abs/0709.4600v1
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Sep 23, 2013
09/13
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Giovanni Amelino-Camelia; Giulia Gubitosi; Niccoló Loret; Flavio Mercati; Giacomo Rosati; Paolo Lipari
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We offer a preliminary exploration of the two sides of the challenge provided by the recent OPERA data on superluminal neutrinos. On one side we stress that some aspects of this result are puzzling even from the perspective of the wild quantum-gravity literature, where arguments in favor of the possibility of superluminal propagation have been presented, but not considering the possibility of such a sizeable effect for neutrinos of such low energies. We feel this must encourage particularly...
Source: http://arxiv.org/abs/1109.5172v2
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Sep 22, 2013
09/13
by
Antonino Marciano; Giovanni Amelino-Camelia; Nicola Rossano Bruno; Giulia Gubitosi; Gianluca Mandanici; Alessandro Melchiorri
texts
eye 48
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Several recent studies have considered the implications for astrophysics and cosmology of some possible nonclassical properties of spacetime at the Planck scale. The new effects, such as a Planck-scale-modified energy-momentum (dispersion) relation, are often inferred from the analysis of some quantum versions of Minkowski spacetime, and therefore the relevant estimates depend heavily on the assumption that there could not be significant interplay between Planck-scale and curvature effects. We...
Source: http://arxiv.org/abs/1004.1110v1
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40
Sep 21, 2013
09/13
by
Giulia Gubitosi; Marina Migliaccio; Luca Pagano; Giovanni Amelino-Camelia; Alessandro Melchiorri; Paolo Natoli; Gianluca Polenta
texts
eye 40
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We develop a method to constrain non-isotropic features of Cosmic Microwave Background (CMB) polarization, of a type expected to arise in some models describing quantum gravity effects on light propagation. We describe the expected signatures of this kind of anomalous light propagation on CMB photons, showing that it will produce a non-isotropic birefringence effect, i.e. a rotation of the CMB polarization direction whose observed amount depends in a peculiar way on the observation direction....
Source: http://arxiv.org/abs/1106.6049v1
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Sep 23, 2013
09/13
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Giovanni Amelino-Camelia; Giulia Gubitosi; Antonino Marciano; Pierre Martinetti; Flavio Mercati; Daniele Pranzetti; Ruggero Altair Tacchi
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eye 40
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We summarize here the first results obtained using a technique we recently developed for the Noether analysis of Hopf-algebra spacetime symmetries, including the derivation of conserved charges for field theories in noncommutative spacetimes of canonical or kappa-Minkowski type.
Source: http://arxiv.org/abs/0710.1219v1
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38
Sep 21, 2013
09/13
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Luca Pagano; Paolo de Bernardis; Grazia De Troia; Giulia Gubitosi; Silvia Masi; Alessandro Melchiorri; Paolo Natoli; Francesco Piacentini; Gianluca Polenta
texts
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Cosmic Microwave Background experiments must achieve very accurate calibration of their polarization reference frame to avoid biasing the cosmological parameters. In particular, a wrong or inaccurate calibration might mimic the presence of a gravitational wave background, or a signal from cosmological birefringence, a phenomenon characteristic of several non-standard, symmetry breaking theories of electrodynamics that allow for \textit{in vacuo} rotation if the polarization direction of the...
Source: http://arxiv.org/abs/0905.1651v3
