936 research outputs found
Aspects of the Bosonic Spectral Action: Successes and Challenges
A short introduction on elements of noncommutative geometry, which offers a
purely geometric interpretation of the Standard Model and implies a higher
derivative gravitational theory, is presented. Physical consequences of almost
commutative manifolds are briefly discussed and cosmological consequences of
the gravitational sector, which is shown not to be plagued by linear
instability, are highlighted. Successes and challenges are discussed. A novel
spectral action proposal based on zeta function regularisation is briefly
presented.Comment: 10 pages. Invited talk to appear in the Proceedings of the Corfu
Summer Institute 2015 "School and Workshops on Elementary Particle Physics
and Gravity", 1-27 September 2015, Corfu, Greec
Noncommutative Spectral Geometry: A Short Review
We review the noncommutative spectral geometry, a gravitational model that
combines noncommutative geometry with the spectral action principle, in an
attempt to unify General Relativity and the Standard Model of electroweak and
strong interactions. Despite the phenomenological successes of the model, the
discrepancy between the predicted Higgs mass and the current experimental data
indicate that one may have to go beyond the simple model considered at first.
We review the current status of the phenomenological consequences and their
implications. Since this model lives by construction at high energy scales,
namely at the Grand Unified Theories scale, it provides a natural framework to
investigate early universe cosmology. We briefly review some of its
cosmological consequences.Comment: 11 pages. Invited talk in the Sixth International Workshop DICE2012,
Castello Pasquini/Castiglioncello (Tuscany), September 17-21, 201
The role of topologigal defects in cosmology
Topological defects are involved in a plethora of physical and astrophysical
phenomena. In these lectures, I will review the r\^ ole they could play in the
large-scale structure formation and the anisotropies of the cosmic microwave
background, as well as in various high energy phenomena, including baryon
number asymmetry, ultra-high energy cosmic rays, and gamma ray bursts. I will
then summarize the gravitational effects of cosmic strings. Finally, I will
briefly discuss the r\^ ole of topological defects in brane world cosmology.Comment: Invited lectures in the NATO ASI / COSLAB (ESF) School ``Patterns of
symmetry breaking'', September 2002 (Cracow). 28 page
Inflation and cosmic (super)strings: implications of their intimate relation revisited
We briefly discuss constraints on supersymmetric hybrid inflation models and
examine the consistency of brane inflation models. We then address the
implications for inflationary scenarios resulting from the strong constraints
on the cosmic (super)string tension imposed from the most recent cosmic
microwave background temperature anisotropies data.Comment: 9 pages; Invited talk in the "Quantized Flux in Tightly Knotted and
Linked Systems" workshop in association with the Newton Institute programme
"Topological Dynamics in the Physical and Biological Sciences" -- Isaac
Newton Institute for Mathematical Sciences, Cambridge 3 - 7 December 201
Space-time dimensionality from brane collisions
Collisions and subsequent decays of higher dimensional branes leave behind
three-dimensional branes and anti-branes, one of which could play the role of
our universe. This process also leads to the production of one-dimensional
branes and anti-branes, however their number is expected to be suppressed.
Brane collisions may also lead to the formation of bound states of branes.
Their existence does not alter this result, it just allows for the existence of
one-dimensional branes captured within the three-dimensional ones.Comment: 4 pages, one minor modification to match version to appear in Phys.
Let.
Formation & evolution of cosmic superstrings: a short review
I will briefly review the formation and evolution of cosmic superstrings, in
the context of brane-world cosmological models within M-theory. These objects
can play the role of cosmic strings, offering a variety of astrophysical
consequences, which I will briefly discuss.Comment: 4 pages; invited talk in the workshop on Cosmology-Strings:
Theory-Cosmology-Phenomenology, Corfu (Greece), Sept. 200
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