arXiv subjects

George Chapline

Publications and source records attributed to George Chapline.

At least 19 recordsLinked to original sources

arXiv2024

Predictions for a Low-mass Cutoff for the Primordial Black Hole Mass Spectrum

In this note we outline how a modest violation in the conservation of mass during the merger of two PBHs affects the PBH mass spectrum that we previously obtained using a Boltzmann equation model for the evolution of the mass spectrum with no mass loss. We find that if the initial cosmological redshift is on the order 10$^{12}$, then the fraction of primordial holes with masses greater than $10^{3}$ solar masses appears be close to what is required to provide the seeds for galaxies. In addition we note that as a result of rapid collisions and strong coupling to electromagnetic radiation for temperatures $>$ GeV (Chapline 2018), there will be an effective low mass cutoff in the mass spectrum for PBH masses less than a certain PBH mass less than than $0.1M_{\odot}$. We also point out that this cutoff in the mass spectrum below $\sim 0.1 M_\odot$ can be confirmed by combining future microlensing observations from the Roman Space Telescope and the Vera C. Rubin Observatory with astrometric observations.

astro-ph.CO↗

arXiv2023

Disentangling the Black Hole Mass Spectrum with Photometric Microlensing Surveys

From the formation mechanisms of stars and compact objects to nuclear physics, modern astronomy frequently leverages surveys to understand populations of objects to answer fundamental questions. The population of dark and isolated compact objects in the Galaxy contains critical information related to many of these topics, but is only practically accessible via gravitational microlensing. However, photometric microlensing observables are degenerate for different types of lenses, and one can seldom classify an event as involving either a compact object or stellar lens on its own. To address this difficulty, we apply a Bayesian framework that treats lens type probabilistically and jointly with a lens population model. This method allows lens population characteristics to be inferred despite intrinsic uncertainty in the lens-class of any single event. We investigate this method's effectiveness on a simulated ground-based photometric survey in the context of characterizing a hypothetical population of primordial black holes (PBHs) with an average mass of $30 M_{\odot}$. On simulated data, our method outperforms current black hole (BH) lens identification pipelines and characterizes different subpopulations of lenses while jointly constraining the PBH contribution to dark matter to ${\approx}25$\%. Key to robust inference, our method can marginalize over population model uncertainty. We find the lower mass cutoff for stellar origin BHs, a key observable in understanding the BH mass gap, particularly difficult to infer in our simulations. This work lays the foundation for cutting-edge PBH abundance constraints to be extracted from current photometric microlensing surveys.

astro-ph.IM↗

arXiv2020

A Reanalysis of Public Galactic Bulge Gravitational Microlensing Events from OGLE-III and IV

Modern surveys of gravitational microlensing events have progressed to detecting thousands per year. Surveys are capable of probing Galactic structure, stellar evolution, lens populations, black hole physics, and the nature of dark matter. One of the key avenues for doing this is studying the microlensing Einstein radius crossing time distribution ($t_E$). However, systematics in individual light curves as well as over-simplistic modeling can lead to biased results. To address this, we developed a model to simultaneously handle the microlensing parallax due to Earth's motion, systematic instrumental effects, and unlensed stellar variability with a Gaussian Process model. We used light curves for nearly 10,000 OGLE-III and IV Milky Way bulge microlensing events and fit each with our model. We also developed a forward model approach to infer the timescale distribution by forward modeling from the data rather than using point estimates from individual events. We find that modeling the variability in the baseline removes a source of significant bias in individual events, and previous analyses over-estimated the number of long timescale ($t_E>100$ days) events due to their over simplistic models ignoring parallax effects and stellar variability. We use our fits to identify hundreds of events that are likely black holes.

astro-ph.GA↗

arXiv2019

Probing the Fundamental Nature of Dark Matter with the Large Synoptic Survey Telescope

Astrophysical and cosmological observations currently provide the only robust, empirical measurements of dark matter. Future observations with Large Synoptic Survey Telescope (LSST) will provide necessary guidance for the experimental dark matter program. This white paper represents a community effort to summarize the science case for studying the fundamental physics of dark matter with LSST. We discuss how LSST will inform our understanding of the fundamental properties of dark matter, such as particle mass, self-interaction strength, non-gravitational couplings to the Standard Model, and compact object abundances. Additionally, we discuss the ways that LSST will complement other experiments to strengthen our understanding of the fundamental characteristics of dark matter. More information on the LSST dark matter effort can be found at https://lsstdarkmatter.github.io/ .

astro-ph.CO↗

arXiv2019

Dark Matter Science in the Era of LSST

Astrophysical observations currently provide the only robust, empirical measurements of dark matter. In the coming decade, astrophysical observations will guide other experimental efforts, while simultaneously probing unique regions of dark matter parameter space. This white paper summarizes astrophysical observations that can constrain the fundamental physics of dark matter in the era of LSST. We describe how astrophysical observations will inform our understanding of the fundamental properties of dark matter, such as particle mass, self-interaction strength, non-gravitational interactions with the Standard Model, and compact object abundances. Additionally, we highlight theoretical work and experimental/observational facilities that will complement LSST to strengthen our understanding of the fundamental characteristics of dark matter.

astro-ph.CO↗

arXiv2016

Was there a negative vacuum energy in your past?

A model for gravitational collapse where the event horizon is a quantum critical phase transition is extended to provide an explanation for the origin of the observable universe, where the expanding universe that we observe today was proceeded by a flat universe with a negative cosmological constant. In principal this allows one derive all the features of our universe from a single parameter: the magnitude of the pre-big bang negative vacuum energy density. In this paper a simple model for the big bang is introduced which allows us to relate the present day energy density and temperature fluctuations of the CMB, to the present day density of dark matter. This model for the big bang also makes a dramatic prediction: dark matter mostly consists of compact objects with a masses on the order of 10^4 solar masses. Remarkably this is consistent with numerical simulations for how primordial fluctuations in the density of dark give rise to the observed inhomogeneous distribution of matter in our universe. Our model for the big bang also allows for the production of some compact objects with masses greater than 10^4 solar masses, which is consistent with numerical simulations of structure formation which require massive primordial comapact objects as the seeds for galaxies in order to explain galactic morphologies.

gr-qc↗

arXiv2015

Leech Lattice Extension of the Non-linear Schrodinger Equation Theory of Einstein spaces

Although the nonlinear Schrodinger equation description of Einstein spaces has provided insights into how quantum mechanics might modify the classical general relativistic description of space-time, an exact quantum description of space-times with matter has remained elusive. In this note we outline how the nonlinear Schrodinger equation theory of Einstein spaces might be generalized to include matter by transplanting the theory to the 25+1 dimensional Lorentzian Leech lattice. Remarkably when a hexagonal section of the Leech lattice is set aside as the stage for the nonlinear Schrodinger equation, the discrete automorphism group of the complex Leech lattice with one complex direction fixed can be lifted to continuous Lie group symmetries. In this setting the wave function becomes an 11x11 complex matrix which represents matter degrees of freedom consisting of a 2-form abelian gauge field and vector nonabelian SU(3)xE6 gauge fields together with their supersymmetric partners. The lagrangian field equations for this matrix wave function appear to be a promising starting point for resolving the unphysical features inherent in the general relativistic descriptions of gravitational collapse and the big bang.

gr-qc↗

arXiv2014

Superfluid Picture for Rotating Space-Times

A new prescription, in the framework of condensate models for space-times, for physical stationary gravitational fields is presented. We show that the spinning cosmic string metric describes the gravitational field associated with the single vortex in a superfluid condensate model for space-time outside the vortex core. This metric differs significantly from the usual acoustic metric for the Onsager-Feynman vortex. We also consider the question of what happens when many vortices are present, and show that on large scales a Gödel-like metric emerges. In both the single and multiple vortex cases the failure of general relativity exemplified by the presence of closed time-like curves is attributed to the breakdown of superfluid rigidity.

gr-qc↗

arXiv2013

Collective baryon decay and gravitational collapse

While it is widely believed that the gravitational collapse of a sufficiently large mass will lead to a density singularity and an event horizon, we propose that this never happens when quantum effects are taken into account. In particular, we propose that when the conditions become ripe for a trapped surface to form, a quantum critical surface sweeps over the collapsing body, transforming the nucleons in the collapsing matter into a lepton/photon gas together with a positive vacuum energy. This will happen regardless of the matter density at the time a trapped surface starts to form, and as a result we predict that at least in all cases of gravitational collapse involving ordinary matter, a large fraction of the rest mass of the collapsing matter will be converted into a burst of neutrinos, and γ-rays. We predict that the peak luminosity of these bursts is only weakly dependent on the mass of the collapsing object, and is on the order of (ε_q/m_Pc^2)^1/4c^5/G, where ε_q is the mean energy of a nucleon parton and m_P is the Planck mass. The duration of the bursts will depend the mass of the collapsing objects; in the case of stellar core collapse we predict that the duration of both the neutrino and γ-ray bursts will be on the order of 10 seconds.

astro-ph.HE↗

arXiv2012

Can a closed critical surface in a quark-gluon plasma serve as a model for the behavior of quantum gravity near to an event horizon?

Time stands still at a quantum critical point in the sense that correlation functions near to the critical point are approximately independent of frequency. In the case of a quantum liquid this would imply that classical hydrodynamics breaks down near to the critical point, revealing the underlying quantum degrees of freedom. An opportunity to see this effect for the first time in the laboratory may be provided by relativistic heavy ion collisions that are tuned so that the quark-gluon plasma passes through its critical point forming a closed critical surface. In this note we point out that in certain kinds of quantum fluids the temperature of a spherical critical surface will be proportional to (radius)-1 and the entropy inside the surface will be close to the Bekenstein bound. In these cases the breakdown in hydrodynamics near to the critical point might serve as a model for the behavior of quantum gravity near to an event horizon. Such a possibility is a fortiori notable because general relativity predicts that nothing should happen at an event horizon.

gr-qc↗

arXiv2012

Magnetosphere of a spinning string

In this note we observe that the exact Maxwell-Einstein equations in the background metric of a spinning string can be solved analytically. This allows us to construct an analytical model for the magnetosphere which is approximately force free near to the spinning string. As in the case of a Kerr black hole in the presence of an external magnetic field the spinning string will acquire an electric charge which depends on the vorticity carried by the spinning string. The self-generated magnetic field and currents strongly resemble the current and magnetic field structure of the jets associated with active galaxies as they emerge from the galactic center.

astro-ph.HE↗

arXiv2010

Dark Energy Stars and the Cosmic Microwave Background

An initial state for the observable universe consisting of a finite region with a large vacuum energy will break-up due to near horizon quantum critical fluctuations. This will lead to a Friedmann-like early universe consisting of an expanding cloud of dark energy stars and radiation. In this note we point out that this scenario provides a simple explanation for the present day density of dark matter as well as the level of CMB temperature flucuations. It is also predicted that all dark matter will be clumped on mass scales ~ 10E3 solar masses.

astro-ph.CO↗

arXiv2010

Dark Energy Stars, AdS/CFT, and High Tc

As developed previously the physical behavior of space-time near to an event horizon can be surmised from the behavior of a superfluid near to a critical point where the speed of sound vanishes. In this talk we note that this critical behavior can be given a geometrical interpretation by regarding the tuning parameter as a radial coordinate for anti-de Sitter space. We also draw attention to a mathematical model for a layered conductor with strong spin-orbit interactions which provides a physical explanation for why the behavior of space-time near an event horizon is related to the behavior of high Tc superconductors.

gr-qc↗

arXiv2009

Superfluidity and Stationary Space-Times

A connection between superfluidity and gravitation is established for physical stationary gravitational fields. We show that the spinning cosmic string metric describes the gravitational field associated with the single vortex in a superfluid condensate model for space-time outside the vortex core. This metric differs significantly from the usual acoustic metric for the Onsager-Feynman vortex. We also consider the question of what happens when many vortices are present, and show that on large scales a Gödel-like metric emerges. In both the single and multiple vortex cases the presence of closed time-like curves is attributed to the breakdown of superfluid rigidity.

hep-th↗

arXiv2009

Dark Energy Stars and AdS/CFT

The theory of dark energy stars illustrates how the behavior of matter near to certain kinds of quantum critical phase transitions can be given a geometrical interpretation by regarding the criticality tuning parameter as an extra dimension. In the case of a superfluid with vanishing speed of sound, the implied geometry resembles 5-dimensional anti-de-Sitter. In a dark energy star this geometry applies both inside and outside the horizon radius, so the AdS-CFT correspondence is consistent with the idea that the surface of a compact astrophysical object represents a quantum critical phase transition of space-time. The superfluid transition in a chiron gas, which was originally proposed as a theory of high temperature superconductivity, may provide an exact theory of this transition.

gr-qc↗

arXiv2009

On the appearance of compact objects at radio and optical frequencies

In the dark energy star picture a compact object is transparent at radio and optical frequencies, and acts as a defocusing lens. Thus the object itself appears as a luminous disk whose surface brightness reflects the surface brightness of the background. In the case of rotating dark energy stars the image will also contain background independent emission features. In this note we provide simple analytic formulae for the separation of these features as a function of angular momentum and viewing angle. In the case of rapid rotation these features will appear to lie within the shadow expected if the compact object were a black hole.

astro-ph.HE↗

arXiv2009

Topological Quantum Image Analysis

A new approach to analyzing visual images is proposed, based on the idea of converting an optical image into a spatially varying pattern of polarized squeezed light, which is then used to produce a pattern of chiral edge currents in a thin film topological insulator. Thin films of Bi or Bi doped with Sb which are punctured with an array of sub-micron holes may be a way of realizing this kind of optical quantum information processing.

quant-ph↗

arXiv2008

Quantum Criticality and the Alpha/Delta Puzzle

In this paper we suggest a novel explanation for the alpha-delta transition in plutonium based on an analogy between the evolution of the actinide ground state as a function of spin orbit coupling and the behaviour of thin film superconductors in a magnetic field. The key point is that in metals with a low carrier density spin-orbit interactions give rise to low energy monopole-like solitons with quantized spin currents, which play much the same role as Abrikosov vortices in thin film superconductors. In alpha-plutonium these solitons form an ordered solid, while in impurity stabilized delta-plutonium they form a pair condensate.

cond-mat.supr-con↗