561 research outputs found
Gravity from Dirac Eigenvalues
We study a formulation of euclidean general relativity in which the dynamical
variables are given by a sequence of real numbers , representing
the eigenvalues of the Dirac operator on the curved spacetime. These quantities
are diffeomorphism-invariant functions of the metric and they form an infinite
set of ``physical observables'' for general relativity. Recent work of Connes
and Chamseddine suggests that they can be taken as natural variables for an
invariant description of the dynamics of gravity. We compute the Poisson
brackets of the 's, and find that these can be expressed in terms
of the propagator of the linearized Einstein equations and the energy-momentum
of the eigenspinors. We show that the eigenspinors' energy-momentum is the
Jacobian matrix of the change of coordinates from the metric to the
's. We study a variant of the Connes-Chamseddine spectral action
which eliminates a disturbing large cosmological term. We analyze the
corresponding equations of motion and find that these are solved if the energy
momenta of the eigenspinors scale linearly with the mass. Surprisingly, this
scaling law codes Einstein's equations. Finally we study the coupling to a
physical fermion field.Comment: An enlarged and improved version which will be pubblished in Mod.
Phys. Lett.
Phenomenology of minimal Z' models: from the LHC to the GUT scale
We consider a class of minimal abelian extensions of the Standard Model with
an extra neutral gauge boson at the TeV scale. In these scenarios an
extended scalar sector and heavy right-handed neutrinos are naturally
envisaged. We present some of their striking signatures at the Large Hadron
Collider, the most interesting arising from a decaying to heavy neutrino
pairs as well as a heavy scalar decaying to two Standard Model Higgses. Using
renormalisation group methods, we characterise the high energy behaviours of
these extensions and exploit the constraints imposed by the embedding into a
wider GUT scenario.Comment: 6 pages, 4 figures. Reference list updated. Contribution to the
proceedings of the 8th International Workshop on QCD - Theory and Experiment
(QCD@Work 2016), 27-30 Jun 2016. Martina Franca, Ital
, Higgses and heavy neutrinos in models: from the LHC to the GUT scale
We study a class of non-exotic minimal extensions of the Standard
Model, which includes all scenarios that are anomaly-free with the ordinary
fermion content augmented by one Right-Handed neutrino per generation, wherein
the new Abelian gauge group is spontaneously broken by the non-zero Vacuum
Expectation Value of an additional Higgs singlet field, in turn providing mass
to a state. By adopting the example, whose results can be recast
into those pertaining to the whole aforementioned class, and allowing for both
scalar and gauge mixing, we first extract the surviving parameter space in
presence of up-to-date theoretical and experimental constraints. Over the
corresponding parameter configurations, we then delineate the high energy
behaviour of such constructs in terms of their stability and perturbativity.
Finally, we highlight key production and decay channels of the new states
entering the spectra of this class of models, i.e., heavy neutrinos, a second
Higgs state and the , which are amenable to experimental investigation at
the Large Hadron Collider. We therefore set the stage to establish a direct
link between measurements obtainable at the Electro-Weak scale and the dynamics
of the underlying model up to those where a Grand Unification Theory embedding
a can be realised.Comment: 32 pages, 59 figures, journal versio
Naturalness and Dark Matter Properties of the BLSSM
In this report, we compare the naturalness and Dark Matter (DM) properties of
the Minimal Supersymmetric Standard Model (MSSM) and the Supersymmetric
Standard Model (BLSSM), with universality in both cases. We do this by adopting
standard measures for the quantitative analysis of the Fine-Tuning (FT), at
both low (i.e. supersymmetric (SUSY)) and high (i.e. unification) scales. We
will see a similar level of FT for both models in these scenarios, with a
slightly better FT for the BLSSM at SUSY scales and MSSM at Grand Unification
Theory (GUT) scales. When including DM relic constraints, we drastically
confine the MSSM's parameter space, whereas we still find a large parameter
space available for the non-minimal scenario.Comment: Prepared for proceedings for DIS2017, talk presented by Simon Kin
Six-year transition from conventional to organic farming: effects oncrop production and soil quality
Prospects for Sneutrino Dark Matter in the BLSSM
The Supersymmetric Standard Model (BLSSM) motivates several Dark
Matter (DM) candidates beyond the Minimally Supersymmetric Standard Model
(MSSM). We assess the comparative naturalness of the two models and discuss the
potential detection properties of a particular candidate, the Right-Handed (RH)
sneutrino.Comment: Prepared for proceedings for La Thuile 2018, talk by Simon Kin
Sneutrino Dark Matter in the BLSSM
In the framework of the Supersymmetric Standard Model (BLSSM), we
assess the ability of ground and space based experiments to establish the
nature of its prevalent Dark Matter (DM) candidate, the sneutrino, which could
either be CP-even or -odd. Firstly, by benchmarking this theory construct
against the results obtained by the Planck spacecraft, we extract the portions
of the BLSSM parameter space compliant with relic density data. Secondly, we
show that, based on current sensitivities of the Fermi Large Area Telescope
(FermiLAT) and their future projections, the study of high-energy -ray
spectra will eventually enable us to extract evidence of this DM candidate
through its annihilations into pairs (in turn emitting photons), in
the form of both an integrated flux and a differential energy spectrum which
cannot be reconciled with the assumption of DM being fermionic (like, e.g., a
neutralino), although it should not be possible to distinguish between the
scalar and pseudoscalar hypotheses. Thirdly, we show that, while underground
direct detection experiments will have little scope in testing sneutrino DM,
the Large Hadron Collider (LHC) may be able to do so in a variety of
multi-lepton signatures, with and without accompanying jets (plus missing
transverse energy), following data collection during Run 2 and 3.Comment: 16 pages, 8 figure
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