41 research outputs found
Photon Chiral Memory Effect Stored on Celestial Sphere
This work introduces the chiral memory effect on the celestial sphere that
measures the permanent change of electromagnetic fields by spin-dependent
processes in bulk. Unlike the conventional memory effect based on the permanent
soft shift in the gauge field itself, it is a permanent change in its spin
angular momentum. The concept underlying the chiral memory (conventional
memory) effect is optical spin torque (optical force) induction in bulk.
Photons and EM radiation carry angular momentum, which is conserved without
interactions. Chiral interactions with matter, medium, curvature, and theories
with parity violation, i.e., axion-QED, transfers spin angular momentum to EM
fields. In nature, such phenomena occur either on EM radiation (chiral memory)
or in the vacuum of QED (vacuum chiral memory). It can be parametrized in terms
of the photon's topological (axial) current at null infinity. To elude the
gauge ambiguity of the topological current, we use the transverse gauge and
show it is the physical part of the current suggested by its cohomology
structure.Comment: 23+5 pages, 6 Fig
Dark Fermions and Spontaneous violation in -axion Inflation
Remarkably, if was spontaneously broken in the physics of inflation,
fermions would notice and remember it. Based on that, we present a new
(non-thermal) mechanism for generating self-interacting dark Dirac fermions
prior to the Hot Big Bang. The non-Abelian gauge fields and axions are
well-motivated matter contents for the particle physics of inflation. In this
background, we analytical study Dirac fermion doublets charged under the
gauge field and use point-splitting technique to regularize the
currents. We show that the non-trivial -violating vacuum structure of
-axion models naturally leads to an efficient mechanism for generating
massive fermions during inflation. The size of the fermionic backreaction and
the density fraction of dark fermions put upper bounds on the fermion's mass.
For a GUT scale inflation, the generated dark fermions, only gravitationally
coupled to the visible sector, can be as heavy as .Comment: 58 pages, 21 figures, V2: minor corrections and references adde
Chiral Anomaly in SU(2)-Axion Inflation and the New Prediction for Particle Cosmology
Upon embedding the axion-inflation in the minimal left-right symmetric gauge
extension of the SM with gauge group ,
[arXiv:2012.11516] proposed a new particle physics model for inflation. In this
work, we present a more detailed analysis. As a compelling consequence, this
setup provides a new mechanism for simultaneous baryogenesis and right-handed
neutrino creation by the chiral anomaly of in inflation. The lightest
right-handed neutrino is the dark matter candidate. This setup has two unknown
fundamental scales, i.e., the scale of inflation and left-right symmetry
breaking . Sufficient matter
creation demands the left-right symmetry breaking scale happens shortly after
the end of inflation. Interestingly, it prefers left-right symmetry breaking
scales above , which is in the range suggested by the
non-supersymmetric SO(10) Grand Unified Theory with an intermediate left-right
symmetry scale. Although gauge field generates equal amounts of
right-handed baryons and leptons in inflation, i.e. , in the Standard
Model sub-sector . A key aspect of this setup is that
sphalerons are never in equilibrium, and the primordial is conserved
by the Standard Model interactions. This setup yields a deep connection between
CP violation in physics of inflation and matter creation (visible and dark);
hence it can naturally explain the observed coincidences among cosmological
parameters, i.e., and . The -axion inflation comes with a cosmological smoking
gun; chiral, non-Gaussian, and blue-tilted gravitational wave background, which
can be probed by future CMB missions and laser interferometer detectors.Comment: 28+20 Pages, 15 Fig
Production and Backreaction of Fermions from Axion- Gauge Fields during Inflation
gauge fields and axions can have a stable, isotropic and homogeneous
configuration during inflation. However, couplings to other matter species lead
to particle production, which in turn induces backreaction on and
destabilization of the non-abelian and axion background. In this paper, we
first study the particle production by a gauge field coupled to a
massive Dirac doublet. To carry out this calculation we have made two technical
improvements compared to what has been done in the literature. First, we apply
the anti-symmetrization of the operators to treat particles and anti-particles
on equal footing, second, to deal with the UV divergences, we apply
instantaneous subtraction. We find that, the backreaction of produced fermions
on the background is negligible for model parameters of observational
interest. Next, we consider production of fermions due to coupling to the
axion. The tree-level backreaction on the gauge fields, as well as on the
axion, is vanishingly small. We also provide an estimate for the loop effects.Comment: Matches version accepted for publication in PR
How attractive is the isotropic attractor solution of axion-SU(2) inflation?
The key to the phenomenological success of inflation models with axion and
SU(2) gauge fields is the isotropic background of the SU(2) field. Previous
studies showed that this isotropic background is an attractor solution during
inflation starting from anisotropic (Bianchi Type I) spacetime; however, not
all possible initial anisotropic parameter space was explored. In this paper,
we explore more generic initial conditions without assuming the initial
slow-roll dynamics. We find some initial anisotropic parameter space which does
not lead to the isotropic background, but to violation of slow-roll conditions,
terminating inflation prematurely. The basin of attraction increases when we
introduce another scalar field acting as inflaton and make the axion-SU(2)
system a spectator sector. Therefore, the spectator axion-SU(2) model is
phenomenologically more attractive.Comment: 22 pages, 9 figures. Updated to version accepted by JCA