19 research outputs found
PSpectRe: A Pseudo-Spectral Code for (P)reheating
PSpectRe is a C++ program that uses Fourier-space pseudo-spectral methods to
evolve interacting scalar fields in an expanding universe. PSpectRe is
optimized for the analysis of parametric resonance in the post-inflationary
universe, and provides an alternative to finite differencing codes, such as
Defrost and LatticeEasy. PSpectRe has both second- (Velocity-Verlet) and
fourth-order (Runge-Kutta) time integrators. Given the same number of spatial
points and/or momentum modes, PSpectRe is not significantly slower than finite
differencing codes, despite the need for multiple Fourier transforms at each
timestep, and exhibits excellent energy conservation. Further, by computing the
post-resonance equation of state, we show that in some circumstances PSpectRe
obtains reliable results while using substantially fewer points than a finite
differencing code. PSpectRe is designed to be easily extended to other problems
in early-universe cosmology, including the generation of gravitational waves
during phase transitions and pre-inflationary bubble collisions. Specific
applications of this code will be pursued in future work.Comment: 22 pages; source code for PSpectRe available:
http://easther.physics.yale.edu v2 Typos fixed, minor improvements to
wording; v3 updated as per referee comment
The importance of secondary halos for strong lensing in massive galaxy clusters across redshift
Cosmological cluster-scale strong gravitational lensing probes the mass distribution of the dense cores of massive dark matter halos and the structures along the line of sight from background sources to the observer. It is frequently assumed that the primary lens mass dominates the lensing, with the contribution of secondary masses along the line of sight being neglected. Secondary mass structures may, however, affect both the detectability of strong lensing in a given survey and modify the properties of the lensing that is detected. This paper focuses on the former: we utilize a large cosmological N-body simulation and a multiple lens plane (and many source plane) ray-tracing technique to quantify the influence of line of sight structures on the detectability of cluster-scale strong lensing in a cluster sample with a mass limit that encompasses current cluster catalogs from the South Pole Telescope. We extract both primary and secondary halos from the "Outer Rim" simulation and consider two strong lensing realizations-one with only the primary halos included, and the other with the full mass light cone for each primary halo, including all secondary halos down to a mass limit more than an order of magnitude smaller than the smallest primary halos considered. In both cases, we use the same source information extracted from the Hubble Ultra Deep Field, and create realistic lensed images consistent with moderately deep ground-based imaging; the statistics of the observed strong lensing are extracted from these simulated images. The results demonstrate that down to the mass limit considered the total number of lenses is boosted by ∼ 13 − 21% when considering the complete multi-halo light-cone; the enhancement is insensitive to different length-to-width cuts applied to the lensed arcs. The increment in strong lens counts peaks at lens redshifts of z ∼ 0.6 with no significant effect at z < 0.3. The strongest trends are observed relative to the primary halo mass, with no significant effect in the most massive quintile of the halo sample, but increasingly boosting the observed lens counts toward small primary halo masses, with an enhancement greater than 50% in the least massive quintile of the halo masses considered
CosmoDC2: A Synthetic Sky Catalog for Dark Energy Science with LSST
This paper introduces cosmoDC2, a large synthetic galaxy catalog designed to
support precision dark energy science with the Large Synoptic Survey Telescope
(LSST). CosmoDC2 is the starting point for the second data challenge (DC2)
carried out by the LSST Dark Energy Science Collaboration (LSST DESC). The
catalog is based on a trillion-particle, 4.225 Gpc^3 box cosmological N-body
simulation, the `Outer Rim' run. It covers 440 deg^2 of sky area to a redshift
of z=3 and is complete to a magnitude depth of 28 in the r-band. Each galaxy is
characterized by a multitude of properties including stellar mass, morphology,
spectral energy distributions, broadband filter magnitudes, host halo
information and weak lensing shear. The size and complexity of cosmoDC2
requires an efficient catalog generation methodology; our approach is based on
a new hybrid technique that combines data-driven empirical approaches with
semi-analytic galaxy modeling. A wide range of observation-based validation
tests has been implemented to ensure that cosmoDC2 enables the science goals of
the planned LSST DESC DC2 analyses. This paper also represents the official
release of the cosmoDC2 data set, including an efficient reader that
facilitates interaction with the data
Gravitational waves from oscillon preheating
Oscillons are long-lived, localized excitations of nonlinear scalar fields which may be copiously produced during preheating after inflation, leading to a possible oscillon-dominated phase in the early Universe. For example, this can happen after axion monodromy inflation, on which we run our simulations. We investigate the stochastic gravitational wave background associated with an oscillon-dominated phase. An isolated oscillon is spherically symmetric and does not radiate gravitational waves, and we show that the flux of gravitational radiation generated between oscillons is also small. However, a significant stochastic gravitational wave background may be generated during preheating itself (i.e, when oscillons are forming), and in this case the characteristic size of the oscillons is imprinted on the gravitational wave power spectrum, which has multiple, distinct peaks
Recommended from our members
CosmoDC2: A Synthetic Sky Catalog for Dark Energy Science with LSST
This paper introduces cosmoDC2, a large synthetic galaxy catalog designed to
support precision dark energy science with the Large Synoptic Survey Telescope
(LSST). CosmoDC2 is the starting point for the second data challenge (DC2)
carried out by the LSST Dark Energy Science Collaboration (LSST DESC). The
catalog is based on a trillion-particle, 4.225 Gpc^3 box cosmological N-body
simulation, the `Outer Rim' run. It covers 440 deg^2 of sky area to a redshift
of z=3 and is complete to a magnitude depth of 28 in the r-band. Each galaxy is
characterized by a multitude of properties including stellar mass, morphology,
spectral energy distributions, broadband filter magnitudes, host halo
information and weak lensing shear. The size and complexity of cosmoDC2
requires an efficient catalog generation methodology; our approach is based on
a new hybrid technique that combines data-driven empirical approaches with
semi-analytic galaxy modeling. A wide range of observation-based validation
tests has been implemented to ensure that cosmoDC2 enables the science goals of
the planned LSST DESC DC2 analyses. This paper also represents the official
release of the cosmoDC2 data set, including an efficient reader that
facilitates interaction with the data