1,012 research outputs found
Inflationary dynamics of kinetically-coupled gauge fields
We investigate the inflationary dynamics of two kinetically-coupled massless
gauge fields with time-varying kinetic-term coefficients. Ensuring that
the system does not have strongly coupled regimes shrinks the parameter space.
Also, we further restrict ourselves to systems that can be quantized using the
standard creation, annihilation operator algebra. This second constraint limits
us to scenarios where the system can be diagonalized into the sum of two
decoupled, massless, vector fields with a varying kinetic-term coefficient.
Such a system might be interesting for magnetogenesis because of how the
strong coupling problem generalizes. We explore this idea by assuming that one
of the gauge fields is the Standard Model field and that the other dark
gauge field has no particles charged under its gauge group. We consider whether
it would be possible to transfer a magnetic field from the dark sector,
generated perhaps before the coupling was turned on, to the visible sector. We
also investigate whether the simple existence of the mixing provides more
opportunities to generate magnetic fields. We find that neither possibility
works efficiently, consistent with the well-known difficulties in inflationary
magnetogenesis.Comment: 17 pages, 0 figures. Matches JCAP versio
Patient Observers and Non-perturbative Infrared Dynamics in Inflation
We have previously derived the effect of soft graviton modes on the quantum
state of de Sitter using spontaneously broken asymptotic symmetries. In the
present paper we reinterpret this effect in terms of particle production and
relate the quantum states with and without soft modes by means of Bogoliubov
transformations. This also enables us to address the much discussed issues
regarding the observability of infrared effects in de Sitter from a new
perspective. While it is commonly agreed that infrared effects are not visible
to a single sub-horizon observer at late times, we argue that the question is
less trivial for a {\it patient observer} who has lived long enough to have a
record of the state before the soft mode was created. Though classically there
is no obstruction to measuring this effect locally, we give several indications
that quantum mechanical uncertainties may censor the effect. We then apply our
methods to find a non-perturbative description of the quantum state pertaining
to the Page time of de Sitter, and derive with these new methods the
probability distribution for the local quantum states of de Sitter and
slow-roll inflation in the presence of long modes. Finally, we use this to
formulate a precise criterion for the existence of eternal inflation in general
classes of slow-roll inflation.Comment: 37 page
Thermalized axion inflation: Natural and monomial inflation with small r
A safe way to reheat the Universe, in models of natural and quadratic inflation, is through shift symmetric couplings between the inflaton Ο and the Standard Model (SM), since they do not generate loop corrections to the potential V ( Ο ) . We consider such a coupling to SM gauge fields, of the form Ο F F / f , with sub-Planckian f . In this case, gauge fields can be exponentially produced already during inflation and thermalize via interactions with charged particles, as pointed out in previous work. This can lead to a plasma of temperature T during inflation, and the thermal masses g T of the gauge bosons can equilibrate the system. In addition, inflaton perturbations Ξ΄ Ο can also have a thermal spectrum if they have sufficiently large cross sections with the plasma. In this case, inflationary predictions are strongly modified: (1) scalar perturbations are thermal, and so enhanced over the vacuum, leading to a generic way to suppress the tensor-to-scalar ratio r ; (2) the spectral index is n s β 1 = Ξ· β 4 Ξ΅ . After presenting the relevant conditions for thermalization, we show that thermalized natural and monomial models of inflation agree with present observations and have r β 10 β 3 β 10 β 2 , which is within reach of next generation CMB experiments
- β¦