Showing papers by "Jeremy Sakstein published in 2021"
TL;DR: In this article, a survey of the constraints on modified-gravity models using astrophysical objects in the cosmological, weak-field regime is presented, embedded in the framework of the novel probes project, a forum connecting observers and theorists involved in the study of dark sector interactions.
Abstract: Modern instruments and observational programs in astrophysics and cosmology have opened new perspectives for probing general relativity on previously unexplored scales. This review provides both a methodological and an observational survey of the constraints on modified-gravity models using astrophysical objects in the cosmological, weak-field regime. It is embedded in the framework of the novel probes project, a forum connecting observers and theorists involved in the study of astrophysical tests of dark sector interactions.
71 citations
TL;DR: In this paper, the authors explore the prospect for direct detection of dark energy by current and upcoming terrestrial dark matter direct detection experiments, and examine whether the electron recoil excess recently reported by the XENON1T collaboration can be explained by chameleon-screened dark energy, and find that such a model is preferred over the background-only hypothesis at the $2.0 ε-ensuremath{sigma} level, in a large range of parameter space not excluded by stellar (or other) probes.
Abstract: We explore the prospects for direct detection of dark energy by current and upcoming terrestrial dark matter direct detection experiments. If dark energy is driven by a new light degree of freedom coupled to matter and photons then dark energy quanta are predicted to be produced in the Sun. These quanta free-stream toward Earth where they can interact with Standard Model particles in the detection chambers of direct detection experiments, presenting the possibility that these experiments could be used to test dark energy. Screening mechanisms, which suppress fifth forces associated with new light particles, and are a necessary feature of many dark energy models, prevent production processes from occurring in the core of the Sun, and similarly, in the cores of red giant, horizontal branch, and white dwarf stars. Instead, the coupling of dark energy to photons leads to production in the strong magnetic field of the solar tachocline via a mechanism analogous to the Primakoff process. This then allows for detectable signals on Earth while evading the strong constraints that would typically result from stellar probes of new light particles. As an example, we examine whether the electron recoil excess recently reported by the XENON1T collaboration can be explained by chameleon-screened dark energy, and find that such a model is preferred over the background-only hypothesis at the $2.0\ensuremath{\sigma}$ level, in a large range of parameter space not excluded by stellar (or other) probes. This raises the tantalizing possibility that XENON1T may have achieved the first direct detection of dark energy. Finally, we study the prospects for confirming this scenario using planned future detectors such as XENONnT, PandaX-4T, and LUX-ZEPLIN.
23 citations
TL;DR: In this article, a novel black hole mass function was proposed to model the physics of star formation and pair instability supernova with a minimal number of parameters. But the model was not applied to the LIGO-Virgo GWTC-2 catalog.
Abstract: We introduce a novel black hole mass function which realistically models the physics of star formation and pair instability supernova with a minimal number of parameters. Applying this to all events in the LIGO-Virgo GWTC-2 catalog, we detect a peak at M_BHMG = 74.8^{+4.3}_{-8.0} MS, followed by a break in the mass function. Repeating the analysis without the black holes from the event GW190521, we find this feature at M_BHMG = 55.4^{+3.0}_{-6.1} MS. The latter result establishes the edge of the anticipated "black hole mass gap" at a value compatible with the expectation from standard stellar structure theory, while the former result is ~ 20MS higher, which would have far-reaching implications if confirmed. Using Bayesian techniques, we establish that our mass function fits a new catalog of black hole masses approximately as well as the pre-existing phenomenological mass functions. We also remark on the implications of these results for constraining or discovering new phenomena in nuclear and particle physics.
21 citations
TL;DR: In this paper, a new particle that couples to the Standard Model, such as an axion, acts as an additional source of loss in the cores of population-III stars, suppressing mass lost due to winds and quenching the pair instability.
20 citations
TL;DR: In this article, a novel black hole mass function was proposed to model the physics of star formation and pair instability supernova with a minimal number of parameters. But the model was not applied to the LIGO-Virgo GWTC-2 catalog.
Abstract: We introduce a novel black hole mass function which realistically models the physics of star formation and pair instability supernova with a minimal number of parameters. Applying this to all events in the LIGO-Virgo GWTC-2 catalog, we detect a peak at M_BHMG = 74.8^{+4.3}_{-8.0} MS, followed by a break in the mass function. Repeating the analysis without the black holes from the event GW190521, we find this feature at M_BHMG = 55.4^{+3.0}_{-6.1} MS. The latter result establishes the edge of the anticipated "black hole mass gap" at a value compatible with the expectation from standard stellar structure theory, while the former result is ~ 20MS higher, which would have far-reaching implications if confirmed. Using Bayesian techniques, we establish that our mass function fits a new catalog of black hole masses approximately as well as the pre-existing phenomenological mass functions. We also remark on the implications of these results for constraining or discovering new phenomena in nuclear and particle physics.
16 citations
TL;DR: In this article, a Markov chain Monte Carlo analysis of the parameter space including all relevant nuisance parameters was performed to constrain the gravitational constant in the Large Magellanic Cloud relative to the Solar System.
Abstract: We perform a novel test of general relativity by measuring the gravitational constant in the Large Magellanic Cloud (LMC). The LMC contains six well-studied Cepheid variable stars in detached eclipsing binaries. Radial velocity and photometric observations enable a complete orbital solution, and precise measurements of the Cepheids' periods permit detailed stellar modelling. Both are sensitive to the strength of gravity, the former via Kepler's third law and the latter through the gravitational free-fall time. We jointly fit the observables for stellar parameters and the gravitational constant. Performing a full Markov Chain Monte Carlo analysis of the parameter space including all relevant nuisance parameters, we constrain the gravitational constant in the Large Magellanic Cloud relative to the Solar System to be ${G}_{\mathrm{LMC}}/{G}_{\mathrm{SS}}=0.9{3}_{\ensuremath{-}0.04}^{+0.05}$. We discuss the implications of this 5% measurement of Newton's constant in another galaxy for dark energy and modified gravity theories. This result excludes one Cepheid, CEP-1812, which is an outlier and needs further study: it is either a highly unusual system to which our model does not apply, or it prefers ${G}_{\mathrm{LMC}}l{G}_{\mathrm{SS}}$ at $2.6\ensuremath{\sigma}$. We also obtain new bounds on critical parameters that appear in semianalytic descriptions of stellar processes. In particular, we measure the mixing length parameter to be $\ensuremath{\alpha}=0.9{0}_{\ensuremath{-}0.26}^{+0.36}$ (when assumed to be constant across our sample), and obtain constraints on the parameters describing turbulent dissipation and convective flux.
6 citations