21 research outputs found
Wilson loops, geometric operators and fermions in 3d group field theory
Group field theories whose Feynman diagrams describe 3d gravity with a
varying configuration of Wilson loop observables and 3d gravity with volume
observables at each vertex are defined. The volume observables are created by
the usual spin network grasping operators which require the introduction of
vector fields on the group. We then use this to define group field theories
that give a previously defined spin foam model for fermion fields coupled to
gravity, and the simpler quenched approximation, by using tensor fields on the
group. The group field theory naturally includes the sum over fermionic loops
at each order of the perturbation theory.Comment: 13 pages, many figures, uses psfra
Observables in 3d spinfoam quantum gravity with fermions
We study expectation values of observables in three-dimensional spinfoam
quantum gravity coupled to Dirac fermions. We revisit the model introduced by
one of the authors and extend it to the case of massless fermionic fields. We
introduce observables, analyse their symmetries and the corresponding proper
gauge fixing. The Berezin integral over the fermionic fields is performed and
the fermionic observables are expanded in open paths and closed loops
associated to pure quantum gravity observables. We obtain the vertex amplitudes
for gauge-invariant observables, while the expectation values of gauge-variant
observables, such as the fermion propagator, are given by the evaluation of
particular spin networks.Comment: 32 pages, many diagrams, uses psfrag
Colored Group Field Theory
Group field theories are higher dimensional generalizations of matrix models.
Their Feynman graphs are fat and in addition to vertices, edges and faces, they
also contain higher dimensional cells, called bubbles. In this paper, we
propose a new, fermionic Group Field Theory, posessing a color symmetry, and
take the first steps in a systematic study of the topological properties of its
graphs. Unlike its bosonic counterpart, the bubbles of the Feynman graphs of
this theory are well defined and readily identified. We prove that this graphs
are combinatorial cellular complexes. We define and study the cellular homology
of this graphs. Furthermore we define a homotopy transformation appropriate to
this graphs. Finally, the amplitude of the Feynman graphs is shown to be
related to the fundamental group of the cellular complex
The complete 1/N expansion of colored tensor models in arbitrary dimension
In this paper we generalize the results of [1,2] and derive the full 1/N
expansion of colored tensor models in arbitrary dimensions. We detail the
expansion for the independent identically distributed model and the topological
Boulatov Ooguri model
Statefinder Diagnostic for Dilaton Dark Energy
Statefinder diagnostic is a useful method which can differ one dark energy
model from the others. The Statefinder pair is algebraically related
to the equation of state of dark energy and its first time derivative. We apply
in this paper this method to the dilaton dark energy model based on Weyl-Scaled
induced gravitational theory. We investigate the effect of the coupling between
matter and dilaton when the potential of dilaton field is taken as the Mexican
hat form. We find that the evolving trajectory of our model in the
diagram is quite different from those of other dark energy models.Comment: 6 pages, 4 figures, type errors corrected, reference no. changed,
accepted by Astrophysics and Space Scienc
Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb(-1) of proton-proton collision data at root s=13 TeV
A search for heavy long-lived charged R-hadrons is reported using a data sample corresponding to
3.2 fb−1 of proton–proton collisions at √s = 13 TeV collected by the ATLAS experiment at the Large
Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow
propagation velocities, which are signatures of heavy charged particles travelling significantly slower than
the speed of light. No significant deviations from the expected background are observed. Upper limits at
95% confidence level are provided on the production cross section of long-lived R-hadrons in the mass
range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV,
805 GeV and 890 GeV, respectively