344 research outputs found
Weak Lensing Effect on CMB in the Presence of a Dipole Anisotropy
We investigate weak lensing effect on cosmic microwave background (CMB) in
the presence of dipole anisotropy. The approach of flat-sky approximation is
considered. We determine the functions and that
appear in expressions of the lensed CMB power spectrum in the presence of a
dipole anisotropy. We determine the correction to B-mode power spectrum which
is found to be appreciable at low multipoles (). However, the temperature
and E-mode power spectrum are not altered significantly.Comment: 9 page
Scale Invariance as a Solution to the Cosmological Constant Problem
We show that scale invariance provides a solution to the fine tuning problem
of the cosmological constant. We construct a generalization of the standard
model of particle physics which displays exact quantum scale invariance. The
matter action is invariant under global scale transformations in arbitrary
dimensions. However the gravitational action breaks scale invariance
explicitly. The scale symmetry is broken spontaneously in the matter sector of
the theory. We show that the contribution to the vacuum energy and hence the
cosmological constant is identically zero from the matter sector within the
full quantum theory. However the gravitational sector may give non-zero
contributions to the cosmological constant at loop orders. No fine tuning may
be required at loop orders since the matter sector gives zero contribution to
the cosmological constant. We also show that we do not require full scale
invariance in order to constrain the vacuum energy from the matter sector. We
only require invariance under pseudoscale transformations. Using this idea and
motivated by the concept of unimodular gravity we propose an alternative model.
In this case also we show that matter sector gives exactly zero contribution to
the vacuum energy.Comment: 12 pages, no figure
Cosmological Perturbation Analysis in a Scale Invariant Model of Gravity
We consider a model for gravity that is invariant under global scale
transformations. It includes one extra real scalar field coupled non-minimally
to the gravity fields. In this model all the dimensionful parameters like the
gravitational constant and the cosmological constant etc. are generated by a
solution of the classical equations of motion which breaks scale invariance. In
this paper we demonstrate the stability of such a solution against small
perturbations in a flat FRW background by making a perturbative expansion
around this solution and solving the resulting equations linear in the
perturbations.Comment: 9 pages, 1 figur
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