Amanda Weltman
A5059394128- Cosmology and Gravitation Theories
- Dark Matter and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Black Holes and Theoretical Physics
- Pulsars and Gravitational Waves Research
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Gamma-ray bursts and supernovae
- Atomic and Subatomic Physics Research
- Astronomy and Astrophysical Research
- Superconducting and THz Device Technology
- Noncommutative and Quantum Gravity Theories
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Relativity and Gravitational Theory
- Solar and Space Plasma Dynamics
- Scientific Research and Discoveries
- Scientific Computing and Data Management
- COVID-19 epidemiological studies
- Superconducting Materials and Applications
- Historical Astronomy and Related Studies
- Distributed and Parallel Computing Systems
- Stellar, planetary, and galactic studies
University of Cape Town
2015-2024
Government of Northwest Territories
2024
University of Central Thailand
2023
Yale University
2021-2022
École Polytechnique Fédérale de Lausanne
2022
Memorial University of Newfoundland
2021
ETH Zurich
2021
National Institute for Theoretical Physics
2021
Institute for Advanced Study
2017-2018
Princeton University
2018
The evidence for the accelerated expansion of Universe and time dependence fine-structure constant suggests existence at least one scalar field with a mass order ${H}_{0}.$ If such exists, then it is generally assumed that its coupling to matter must be tuned unnaturally small values in satisfy tests equivalence principle (EP). In this paper, we present an alternative explanation which allows fields evolve cosmologically while having couplings unity. our scenario, depends on local density:...
We present a novel scenario where scalar field acquires mass which depends on the local matter density: is massive Earth, density high, but essentially free in solar system, low. All existing tests of gravity are satisfied. predict that near-future satellite experiments could measure an effective Newton's constant space different from as well violations equivalence principle stronger than currently allowed by laboratory experiments.
We show that the chameleon scalar field can drive current phase of cosmic acceleration for a large class potentials are also consistent with local tests gravity. These provide explicit realizations quintessence model where couples directly to baryons and dark matter gravitational strength. analyze cosmological evolution existence an attractor solution following minimum its effective potential. For wide range initial conditions, spanning many orders magnitude in energy density, is reached...
The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO look for axions or axion-like particles (ALPs) originating in the Sun via Primakoff conversion of solar plasma photons. In terms signal-to-noise ratio, about 4–5 orders magnitude more sensitive than CAST, currently most powerful helioscope, reaching sensitivity to axion-photon couplings down few × 10−12 GeV−1 and thus probing large fraction unexplored ALP parameter space....
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new 400-800MHz radio interferometer under development for deployment in South Africa. HIRAX will comprise 1024 six meter parabolic dishes on compact grid map most of the southern sky over course four years. has two primary science goals: to constrain Dark Energy measure structure at high redshift, study transients pulsars. observe unresolved sources neutral hydrogen via their redshifted 21-cm emission line (`hydrogen...
Following the first two annual intensity mapping workshops at Stanford in March 2016 and Johns Hopkins June 2017, we report on recent advances theory, instrumentation observation that were presented these meetings some of opportunities challenges identified looking forward. With preliminary detections CO, [CII], Lya low-redshift 21cm, a host experiments set to go online next few years, field is rapidly progressing all fronts, with great anticipation for flood new exciting results. This...
Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly compelling possibility for new physics. Nature may contain numerous dark each their own beautiful structure, distinct particles, and forces. This review summarizes physics motivation sectors exciting opportunities experimental exploration. It is summary Intensity Frontier subgroup "New, Light, Weakly-coupled Particles" Community...
Abstract The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over wide range of frequencies, and with an order magnitude greater sensitivity survey speed than any current telescope. SKA will address many important topics in astronomy, ranging from planet formation distant galaxies. However, this work, we consider the perspective as facility for studying physics. We review four areas which expected make major contributions our understanding fundamental...
We review the physics potential of a next generation search for solar axions: International Axion Observatory (IAXO) . Endowed with sensitivity to discover axion-like particles (ALPs) coupling photons as small gaγ∼ 10−12 GeV−1, or electrons gae∼10−13, IAXO has find QCD axion in 1 meV∼1 eV mass range where it solves strong CP problem, can account cold dark matter Universe and be responsible anomalous cooling observed number stellar systems. At same time, will have enough detect lower axions...
Abstract We consider the possible observation of fast radio bursts (FRBs) with planned future telescopes, and investigate how well dispersions redshifts these signals might constrain cosmological parameters. construct mock catalogs FRB dispersion measure (DM) data employ Markov Chain Monte Carlo analysis, which we forecast compare existing constraints in flat ΛCDM model, as some popular extensions that include dark energy equation state curvature find scatter DM observations caused by...
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element to be deployed at the South African Radio Astronomy Observatory (SARAO) Square Kilometer Array (SKA) site Africa. Each of 6m, $f/0.23$ dishes will instrumented dual-polarisation feeds operating over frequency range 400-800 MHz. Through intensity mapping 21 cm emission line neutral hydrogen, HIRAX provide cosmological survey distribution...
We discuss the ground-breaking science that will be possible with a wide area survey, using MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The current specifications of make it great fit for applications require large survey speeds but not necessarily high angular resolutions. In particular, cosmology, over $\sim 4,000 \, {\rm deg}^2$ 4,000$ hours potentially provide first ever measurements baryon acoustic oscillations 21cm intensity mapping technique, enough...
We present 11 detections of FRB 121102 in ~3 hours observations during its 'active' period on the 10th September 2019. The were made using newly deployed MeerTRAP system and single pulse detection pipeline at MeerKAT radio telescope South Africa. Fortuitously, Nancay this day overlapped with last hour resulted 4 simultaneous detections. MeerKAT's wide band receiver, which extends down to relatively low frequencies (900-1670 MHz usable L-band range), have allowed us get a detailed look...
A violation of the reciprocity relation, which induces a distance-duality reflects itself in change normalization cosmic microwave spectrum such way that its is grey. We show existing observational constraints imply relation cannot be violated by more than 0.01% between decoupling and today. compare this effect to other sources relations induce spectral distortion background spectrum.
We report results from a search for chameleon particles created via photon-chameleon oscillations within magnetic field. This experiment is sensitive to wide class of unexplored power-law and dark energy models. These exclude 5 orders magnitude in the coupling chameleons photons covering range 4 effective mass and, individual models, between 12 couplings matter.
We report the first results from GammeV search for chameleon particles, which may be created via photon-photon interactions within a strong magnetic field. Chameleons are hypothesized scalar fields that could explain dark energy problem. implement novel technique to create and trap reflective particles jar detect them later their afterglow as they slowly convert back into photons. These measurements provide experimental constraints on couplings of chameleons
We present a detailed study of the complex time-frequency structure sample previously reported bursts FRB 121102 detected with MeerKAT telescope in September 2019. The wide contiguous bandwidth these observations have revealed bifurcating some at $1250$ MHz. When de-dispersed to their structure-optimised dispersion measures, two show clear deviation from cold plasma relationship below find differential measure ${\sim}1{-}2$ pc cm$^{-3}$ between lower and higher frequency regions each burst....
The GammeV experiment has constrained the couplings of chameleon scalar fields to matter and photons. Here we present a detailed calculation afterglow rate underlying these constraints. dependence constraints on various assumptions in is studied. We discuss GammeV--CHASE, second-generation experiment, which will improve upon several major ways. Using our rate, forecast model-independent achievable by GammeV--CHASE. then apply variety models, including quartic chameleons dark energy models....
Recent precision cosmological parameter constraints imply that the spatial curvature of Universe is essentially dynamically negligible - but only if relatively strong assumptions are made about equation state dark energy (DE). When these relaxed, degeneracies arise make it hard to disentangle DE and curvature, degrading constraints. We show forthcoming 21cm intensity mapping experiments such as HIRAX ideally designed carry out model-independent measurements, they can measure clustering...
In this paper we study various particle physics effects of a light, scalar dark energy field with chameleon-like couplings to matter. We show that chameleon model only matter will induce coupling photons. doing so, derive the first microphysical realization chameleonic coupled electromagnetic strength. This analysis provides additional motivation for current and near-future tests axion-like particles. find new bound on strength chameleons in uniformly models. also effect fields Higgs...