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Deepak Vaid

Publications and source records attributed to Deepak Vaid.

25 records · Page 2Linked to original sources

Non-abelian Gauge Fields from Defects in Spin-Networks

\emph{Effective} gauge fields arise in the description of the dynamics of defects in lattices of graphene in condensed matter. The interactions between neighboring nodes of a lattice/spin-network are described by the Hubbard model whose effective field theory at long distances is given by the Dirac equation for an \emph{emergent} gauge field. The spin-networks in question can be used to describe the geometry experienced by a non-inertial observer in flat spacetime moving at a constant acceleration in a given direction. We expect such spin-networks to describe the structure of quantum horizons of black holes in loop quantum gravity. We argue that the abelian and non-abelian gauge fields of the Standard Model can be identified with the emergent degrees of freedom required to describe the dynamics of defects in symmetry reduced spin-networks.

gr-qc↗

Elementary Particles as Gates for Universal Quantum Computation

It is shown that there exists a mapping between the fermions of the Standard Model (SM) represented as braids in the Bilson-Thompson model, and a set of gates which can perform Universal Quantum Computation (UQC). This leads us to conjecture that the "Computational Universe Hypothesis" (CUH) can be given a concrete implementation in a new physical framework where elementary particles and the gauge bosons (which intermediate interactions between fermions) are interpreted as the components of a quantum computational network, with the particles serving as quantum computational gates and the gauge fields as the information carrying entities.

hep-th↗

Quantum Hall Effect and Black Hole Entropy in Loop Quantum Gravity

In LQG, black hole horizons are described by 2+1 dimensional boundaries of a bulk 3+1 dimensional spacetime. The horizon is endowed with area by lines of gravitational flux which pierce the surface. As is well known, counting of the possible states associated with a given set of punctures allows us to recover the famous Bekenstein-Hawking area law according to which the entropy of a black hole is proportional to the area of the associated horizon $ S_{BH} \propto A_{Hor} $. It is also known that the dynamics of the horizon degrees of freedom is described by the Chern-Simons action of a $\mathfrak{su(2)}$ (or $\mathfrak{u(1)}$ after a certain gauge fixing) valued gauge field $A_μ^i$. Recent numerical work which performs the state-counting for punctures, from first-principles, reveals a step-like structure in the entropy-area relation. We argue that both the presence of the Chern-Simons action and the step-like structure in the entropy-area curve are indicative of the fact that the effective theory which describes the dynamics of punctures on the horizon is that of the Quantum Hall Effect.

gr-qc↗

Embedding the Bilson-Thompson model in an LQG-like framework

We argue that the Quadratic Spinor Lagrangian approach allows us to approach the problem of forming a geometrical condensate of spinorial tetrads in a natural manner. This, along with considerations involving the discrete symmetries of lattice triangulations, lead us to discover that the quasiparticles of such a condensate are tetrahedra with braids attached to its faces and that these braid attachments correspond to the preons in Bilson-Thompson's model of elementary particles. These "spatoms" can then be put together in a tiling to form more complex structures which encode both geometry and matter in a natural manner. We conclude with some speculations on the relation between this picture and the computational universe hypothesis.

hep-th↗

Local Void vs Dark Energy: Confrontation with WMAP and Type Ia Supernovae

It is now a known fact that if we happen to be living in the middle of a large underdense region, then we will observe an "apparent acceleration", even when any form of dark energy is absent. In this paper, we present a "Minimal Void" scenario, i.e. a "void" with minimal underdensity contrast (of about -0.4) and radius (~ 200-250 Mpc/h) that can, not only explain the supernovae data, but also be consistent with the 3-yr WMAP data. We also discuss consistency of our model with various other measurements such as Big Bang Nucleosynthesis, Baryon Acoustic Oscillations and local measurements of the Hubble parameter, and also point out possible observable signatures.

astro-ph↗

A fine tuning free resolution of the cosmological constant problem

In a recent paper we discovered that a fermionic condensate is formed from gravitational interactions due to the covariant coupling of fermions in the presence of a torsion-fermion contact interaction. The condensate gap gives a negative contribution to the bare cosmological constant. In this letter, we show that the cosmological constant problem can be solved without fine tuning of the bare cosmological constant. We demonstrate how a universe with a large initial cosmological constant undergoes inflation, during which time the energy gap grows as the volume of the universe. Eventually the gap becomes large enough to cancel out the bare cosmological term, inflation ends and we end up in a universe with an almost vanishing cosmological term. We provide a detailed numerical analysis of the system of equations governing the self regulating relaxation of the cosmological constant.

hep-th↗

Gravity Induced Chiral Condensate Formation and the Cosmological Constant

It is well known that the covariant coupling of fermionic matter to gravity induces a four-fermion interaction. The presence of this term in a homogenous and isotropic space-time results in a BCS-like Hamiltonian and the formation of a chiral condensate with a mass gap. We calculate the gap ($Δ$) via a mean-field approximation for minimally coupled fermionic fields in a FRW background and find that it depends on the scale factor. The calculation also yields a correction to the bare cosmological constant ($Λ_0$), and a non-zero vev for $<ψ^\dagψ>$ which then behaves as a scalar field. Hence we conjecture that the presence of fermionic matter in gravity provides a natural mechanism for relaxation of the $Λ_0$ and explains the existence of a scalar field from (almost) first principles.

hep-th↗