Seyen Kouwn

Classically scale invariant inflation, supermassive WIMPs, and adimensional gravity

We introduce a minimal and yet comprehensive framework with

Massive Photon and Dark Energy

CP

Dark spinor model with torsion and cosmology

and classical scale symmetries in order to simultaneously address the hierarchy problem, neutrino masses, dark matter, and inflation. One complex gauge singlet scalar and three flavors of the right-handed Majorana neutrinos are added to the standard model content, facilitating the see-saw mechanism, among others. An adimensional theory of gravity (Agravity) is employed, allowing for the trans-Planckian field excursions. The weak and Planck scales are induced by the Higgs portal and the scalar nonminimal couplings, respectively, once a Coleman-Weinberg dynamically generated vacuum expectation value for the singlet scalar is obtained. All scales are free from any mutual quadratic destabilization. The

Large Scale Suppression of Scalar Power on a Spatial Condensation

CP

Cosmological Perturbations of a Quartet of Scalar Fields with a Spatially Constant Gradient

symmetry prevents a decay of the pseudoscalar singlet, rendering it a suitable WIMPzilla dark matter candidate with the correct observational relic abundance. Identifying the pseudo-Nambu-Goldstone boson of the (approximate) scale symmetry with the inflaton field, the model accommodates successful slow-roll inflation, compatible with the observational data. We reach the conclusion that a pseudo-Nambu-Goldstone inflaton, within a classically scale-symmetric framework, yields lighter WIMPzillas.

Homogeneous rolling tachyons in boundary string field theory

We investigate cosmology of massive electrodynamics and explore the possibility whether massive photon could provide an explanation of the dark energy. The action is given by the scalar-vector-tensor theory of gravity which is obtained by non-minimal coupling of the massive Stueckelberg QED with gravity and its cosmological consequences are studied by paying a particular attention to the role of photon mass. We find that the theory allows cosmological evolution where the radiation- and matter-dominated epochs are followed by a long period of virtually constant dark energy that closely mimics

Hawking temperature in Taub-NUT (A)dS spaces via the generalized uncertainty principle

\Lambda

Asymptotically Static Universe

CDM model and the main source of the current acceleration is provided by the nonvanishing photon mass governed by the relation

Exact Solution and Exotic Fluid in Cosmology

\Lambda\sim m^2

Hamiltonian Formalism of Topologically Massive Electrodynamics

. A detailed numerical analysis shows that the nonvanishing photon mass of the order of