Peter Adshead
A5044131605- Cosmology and Gravitation Theories
- Dark Matter and Cosmic Phenomena
- Black Holes and Theoretical Physics
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Computational Physics and Python Applications
- Stochastic processes and financial applications
- Advanced Thermodynamics and Statistical Mechanics
- Atomic and Subatomic Physics Research
- Earth Systems and Cosmic Evolution
- Neutrino Physics Research
- Medical Imaging Techniques and Applications
- Relativity and Gravitational Theory
- Magnetic Properties and Applications
- Stability and Controllability of Differential Equations
- Noncommutative and Quantum Gravity Theories
- Scientific Research and Discoveries
- Biofield Effects and Biophysics
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced MEMS and NEMS Technologies
University of Illinois Urbana-Champaign
2015-2024
University of Pennsylvania
2023
University of Cambridge
2014
Fermi National Accelerator Laboratory
2011-2013
University of Chicago
2011-2013
Yale University
2008-2011
We present the science case, reference design, and project plan for Stage-4 ground-based cosmic microwave background experiment CMB-S4.
This book lays out the scientific goals to be addressed by next-generation ground-based cosmic microwave background experiment, CMB-S4, envisioned consist of dedicated telescopes at South Pole, high Chilean Atacama plateau and possibly a northern hemisphere site, all equipped with new superconducting cameras. CMB-S4 will dramatically advance cosmological studies crossing critical thresholds in search for B-mode polarization signature primordial gravitational waves, determination number...
We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes physics inflation. focus on prospects for using CMB to differentiate various inflationary mechanisms. In particular, a detection primordial B‐mode would demonstrate that inflation occurred at very high energy scale, and inflaton traversed super‐Planckian distance in field space. explain how such or constraint illuminate aspects Planck scale. Moreover, can constrain scale‐dependence...
We propose a model for inflation consisting of an axionic scalar field coupled to set three non-Abelian gauge fields. Our model's novel requirement is that the fields begin with rotationally invariant vacuum expectation value (VEV) preserved through identification SU(2) invariance rotations in dimensions. The VEV interacts background axion, leading attractor solution exhibits slow roll even when axion decay constant has natural ($<{M}_{\mathrm{Pl}}$). Assuming sinusoidal potential we find...
Abstract CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding origin evolution universe. Among science cases pursued with CMB-S4, quest for detecting primordial gravitational waves is a central driver experimental design. This work details development forecasting framework that includes power-spectrum-based semianalytic projection tool, targeted explicitly toward...
Scalar metric fluctuations generically source a spectrum of gravitational waves at second order in perturbation theory, poising wave experiments as potentially powerful probes the small-scale curvature power spectrum. We perform detailed study imprint primordial non-Gaussianity on these induced waves, emphasizing role both disconnected and connected components primoridal trispectrum. Specializing to local-type non-Gaussianity, we numerically compute all contributions present results for...
We consider the running of spectral index as a probe both inflation itself, and overall evolution very early universe. Surveying collection simple single field inflationary models, we confirm that magnitude is relatively consistent, unlike tensor amplitude, which varies by orders magnitude. Given this target, potentially detectable future large scale structure or 21 cm observations, but only most futuristic measurements can distinguish between these models on basis their running. For any...
Models of inflation involving non-Abelian gauge field backgrounds can produce gravitational waves at an observable level with a preferred handedness. This asymmetry comes about because the background generates parity violation in action for perturbations. In specific model we study, chromonatural inflation, these be produced levels even when no makes super-Planckian excursion, thus evading common formulation Lyth bound. Unfortunately, considered concert scalar fluctuations, this chiral...
We provide analytic solutions for the power spectrum and bispectrum of curvature fluctuations produced by a step feature in inflaton potential, valid limit that is short sharp. In this limit, strongly scale dependent its effective non-linearity attains large oscillatory amplitude. The perturbations to spectrum, on other hand, remain small component top usual generated slow roll. utilize our assess observability predicted non-Gaussian signatures show that, if present, only very sharp steps...
We study gravitational wave production during Abelian gauge-field preheating following inflation. consider both scalar and pseudoscalar inflaton models coupled directly to gauge fields via either a dilatonic coupling the kinetic term or an axial Chern-Simons term. In cases waves are produced efficiently phase, with signature louder than most cosmological signals. These can contribute radiation energy budget of Universe at level which will be probed by upcoming cosmic microwave background...
We study the onset of reheating epoch at end axion-driven inflation where axion is coupled to an Abelian, $U(1)$, gauge field via a Chern-Simons interaction term. focus primarily on $m^2\phi^2$ and explore possibility that preheating can occur for range coupling values consistent with recent observations bounds overproduction primordial black holes. find wide parameters efficient. In certain cases inflaton seen transfer all its energy fields within few oscillations. most cases, we...
We study gravitational wave production from gauge preheating in a variety of inflationary models, detailing its dependence on both the energy scale and shape potential. show that into Abelian fields generically leads to large background contributes significantly effective number relativistic degrees freedom early universe, ${N}_{\mathrm{eff}}$. demonstrate efficiency is correlated with tensor-to-scalar ratio, $r$. In particular, we efficient models whose ratio would be detected by...
We demonstrate that gravitational waves generated by efficient gauge preheating after axion inflation generically contribute significantly to the effective number of relativistic degrees freedom N_{eff}. show that, with existing Planck limits, from already place strongest constraints on inflaton's possible axial coupling Abelian fields. can completely reheat Universe regardless inflationary potential. Further, we quantify variation efficiency wave production model and it is correlated...
We describe an efficient scheme for evaluating higher order contributions to primordial cosmological perturbations using the ``in-in'' formalism, which is basis of modern calculations non-Gaussian and spectrum. show that diagrams with two or more vertices require careful handling. present implementation operator formalism in these can be evaluated a simple transparent fashion. illustrate our methodology by correction gravitational wave spectrum generated scalar loops, 2-vertex, 1-loop...
In this work we compute the production of magnetic fields in models axion inflation coupled to hypercharge sector Standard Model through a Chern-Simons interaction term. We make simplest choice quadratic inflationary potential and use lattice simulations calculate field strength, helicity correlation length at end inflation. For small values axion-gauge coupling strength results agree with no-backreaction calculations estimates found literature. larger couplings differs from estimate depends...
We study derivatively coupled fermions in axion-driven inflation, specifically mϕ2ϕ2 and monodromy calculate particle production during the inflationary epoch post-inflationary axion oscillations. During rolling acts as an effective chemical potential for helicity which biases gravitational of one fermion over other. This mechanism allows efficient heavy states that would otherwise be highly suppressed. Following oscillates with both helicities are produced frequency field changes...
In a broad class of theories, the relic abundance dark matter is determined by interactions internal to thermalized sector, with no direct involvement Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was sector initially populated in early universe? Motivated part difficulty accommodating large amounts entropy carried radiation cosmic microwave background measurements effective number relativistic species at recombination, N eff , we aim...
Our current understanding of the Universe is established through pristine measurements structure in cosmic microwave background (CMB) and distribution shapes galaxies tracing large scale (LSS) Universe. One key ingredient that underlies cosmological observables field sources observed assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps most robust theoretical prediction models explain Universe; itis necessarily present even...
Inflation may provide unique insight into the physics at highest available energy scales that cannot be replicated in any realistic terrestrial experiment. Features primordial power spectrum are generically predicted a wide class of models inflation and its alternatives, observationally one most overlooked channels for finding evidence non-minimal inflationary models. Constraints from observations cosmic microwave background cover widest range feature frequencies, but sensitive constraints...
Characterizing the physical properties of stochastic gravitational waves background (SGWB) is a key step towards identifying nature its possible origin. We focus our analysis on SGWB anisotropies. The existence non-trivial primordial scalar-tensor-tensor (STT) correlation in squeezed configuration may be inferred from effect that long wavelength scalar mode has wave power spectrum: an anisotropic contribution. Crucially, such contribution correlated with temperature anisotropies cosmic...
Abstract We study gauge preheating following pseudoscalar-driven inflation in full general relativity. implement the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) scheme to solve nonlinear evolution of metric alongside dynamics pseudoscalar and fields. The background emission gravitational waves are broadly consistent with simulations a Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime. find large, localized overdensities BSSN order δ = δρ / ρ ∼ 30, dimensionless power spectrum peaks above...
We explore the consequences of existence a very large number light scalar degrees freedom in early universe. distinguish between participator and spectator fields. The former have small mass, can contribute to inflationary dynamics; latter are either strictly massless or negligible VEV. In $N$-flation generic assisted inflation scenarios, is cooperative phenomenon driven by $N$ fields, none which could drive on its own. review upper bounds $N$, as function Hubble scale $H$. then consider...