Search

Observations have found black holes spanning ten orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is however provisional as its behavior at infinity is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole's interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over $0

Observations have found black holes spanning 10 orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is, however, provisional as its behavior at infinity is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole's interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over 0 < z less than or similar to 2.5. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at z less than or similar to 7, black holes contribute an effectively constant cosmological energy density to Friedmann's equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of omega(?) measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at z similar to 0.7.

Observations have found black holes spanning 10 orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is, however, provisional as its behavior at infinity is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole's interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over 0 < z less than or similar to 2.5. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at z less than or similar to 7, black holes contribute an effectively constant cosmological energy density to Friedmann's equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of omega(?) measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at z similar to 0.7.

The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since $z\sim1$ can help to diagnose the origins of locally-observed correlations between SMBH mass and stellar mass. We therefore construct three samples of elliptical galaxies, one at $z\sim0$ and two at $0.7\lesssim z \lesssim2.5$, and quantify their relative positions in the $M_{BH}-M_*$ plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of seven between $z\sim1$ and $z\sim0$. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of $\sim20$ at $z\sim 2$. The result is robust against variation in the high and low redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at $z\lesssim 2$, or that selection and measurement biases are both underestimated, and depend on redshift., Comment: ApJ, accepted

We demonstrate a single-parameter route for reproducing higher mass objects as observed in the LIGO--Virgo mass distribution, using only the isolated binary stellar evolution channel. This single parameter encodes the cosmological mass growth of compact stellar remnants that exceed the Tolman-Oppenheimer-Volkoff limit. Cosmological mass growth appears in known solutions to General Relativity with cosmological boundary conditions. We consider the possibility of solutions with cosmological boundary conditions, which reduce to Kerr on timescales short compared to the Hubble time. We discuss complementary observational signatures of these solutions that can confirm or invalidate their astrophysical relevance., Comment: 8 pages, 2 figures. Submitted to ApJL

ObjectiveDecoding neural activity has been limited by the lack of tools available to record from large numbers of neurons across multiple cortical regions simultaneously with high temporal fidelity. To this end, we developed the Argo system to record cortical neural activity at high data rates.ApproachHere we demonstrate a massively parallel neural recording system based on platinum-iridium microwire electrode arrays bonded to a CMOS voltage amplifier array. The Argo system is the highest channel count in vivo neural recording system, supporting simultaneous recording from 65 536 channels, sampled at 32 kHz and 12-bit resolution. This system was designed for cortical recordings, compatible with both penetrating and surface microelectrodes.Main resultsWe validated this system through initial bench testing to determine specific gain and noise characteristics of bonded microwires, followed by in-vivo experiments in both rat and sheep cortex. We recorded spiking activity from 791 neurons in rats and surface local field potential activity from over 30 000 channels in sheep.SignificanceThese are the largest channel count microwire-based recordings in both rat and sheep. While currently adapted for head-fixed recording, the microwire-CMOS architecture is well suited for clinical translation. Thus, this demonstration helps pave the way for a future high data rate intracortical implant.

We demonstrate a single-parameter route for reproducing higher mass objects as observed in the LIGO--Virgo mass distribution, using only the isolated binary stellar evolution channel. This single parameter encodes the cosmological mass growth of compact stellar remnants that exceed the Tolman-Oppenheimer-Volkoff limit. Cosmological mass growth appears in known solutions to General Relativity with cosmological boundary conditions. We consider the possibility of solutions with cosmological boundary conditions, which reduce to Kerr on timescales short compared to the Hubble time. We discuss complementary observational signatures of these solutions that can confirm or invalidate their astrophysical relevance., Comment: 8 pages, 2 figures. Submitted to ApJL

Ultra-high energy cosmic rays (UHECRs) are the most energetic particles observed and serve as a probe of the extreme universe. A key question to understanding the violent processes responsible for their acceleration is identifying which classes of astrophysical objects (active galactic nuclei or starburst galaxies, for example) correlate to their arrival directions. While source clustering is limited by deflections in the Galactic magnetic field, at the highest energies the scattering angles are sufficiently low to retain correlation with source catalogues. While there have been several studies attempting to identify source catalogue correlations with data from the Pierre Auger Observatory and the Telescope Array, the significance above an isotropic background has not yet reached the threshold for discovery. It has been known for several decades that a full-sky UHECR observatory would provide a substantial increase in sensitivity to the anisotropic component of UHECRs. There have been several concepts developed in that time targeting the identification of UHECR sources such as OWL, JEM-EUSO, and POEMMA, using fluorescence detection in the Earth's atmosphere from orbit. In this white paper, we present a concept called the Zettavolt Askaryan Polarimeter (ZAP), designed to identify the source of UHECRs using radio detection of the Askaryan radio emissions produced by UHECRs interacting in the Moon's regolith from low lunar orbit., Comment: 6 pages, 2 figures, letter of interest submitted to Snowmass 2021

We consider some observational consequences of replacing all black holes (BHs) with a class of non-singular solutions that mimic BHs but with Dark Energy (DE) interiors; GEneric Objects of Dark Energy (GEODEs). We focus on the BH mass function and chirp-mass redshift distribution of mergers visible to gravitational wave observatories. We incorporate the GEODE blueshift into an initially Salpeter stellar remnant distribution, and model the binary population by evolving synthesized binary remnant distributions, published before LIGO's first measurements. We find that a GEODE produced between $20 \lesssim z \lesssim 40$, and observed at $z \sim 7$, will have its initial mass amplified by $\sim 20-140\times$. This can relieve tension between accretion-only growth models and the inferred masses of BHs in quasars at $z \gtrsim 6$. Moreover, we find that merger rates of GEODE binaries increase by a factor of $\sim 2\times$ relative to classical BHs. The resulting GEODE mass function is consistent with the most recent LIGO constraints at $< 0.5\sigma$. In contrast, a Salpeter stellar distribution that evolves into classical remnants is in tension at $\gtrsim 2\sigma$. This agreement occurs without low-metallicity regions, abnormally massive progenitor stars, novel formation channels, or primordial object formation at extreme rates. In particular, we find that solar metallicity progenitors, which produce $1.1-1.8\mathrm{M}_\odot$ remnants, overlap with many LIGO observations when evolved as GEODEs., Comment: ApJ accepted

We consider some observational consequences of replacing all black holes (BHs) with a class of non-singular solutions that mimic BHs but with Dark Energy (DE) interiors; GEneric Objects of Dark Energy (GEODEs). We focus on the BH mass function and chirp-mass redshift distribution of mergers visible to gravitational wave observatories. We incorporate the GEODE blueshift into an initially Salpeter stellar remnant distribution, and model the binary population by evolving synthesized binary remnant distributions, published before LIGO's first measurements. We find that a GEODE produced between $20 \lesssim z \lesssim 40$, and observed at $z \sim 7$, will have its initial mass amplified by $\sim 20-140\times$. This can relieve tension between accretion-only growth models and the inferred masses of BHs in quasars at $z \gtrsim 6$. Moreover, we find that merger rates of GEODE binaries increase by a factor of $\sim 2\times$ relative to classical BHs. The resulting GEODE mass function is consistent with the most recent LIGO constraints at $< 0.5\sigma$. In contrast, a Salpeter stellar distribution that evolves into classical remnants is in tension at $\gtrsim 2\sigma$. This agreement occurs without low-metallicity regions, abnormally massive progenitor stars, novel formation channels, or primordial object formation at extreme rates. In particular, we find that solar metallicity progenitors, which produce $1.1-1.8\mathrm{M}_\odot$ remnants, overlap with many LIGO observations when evolved as GEODEs., Comment: ApJ accepted

The Time-Of-Propagation detector is a Cherenkov particle identification detector based on quartz radiator bars for the Belle II experiment at the SuperKEKB electron-positron collider. The purpose of the detector is to identify the type of charged hadrons produced in electron-positron collisions, and requires a single photon timing resolution below 100 picoseconds. A novel front-end electronic system was designed, built, and integrated to acquire data from the 8192 microchannel plate photomultiplier tube channels in the detector. Waveform sampling of these analog signals is done by switched-capacitor array application-specific integrated circuits. The processes of triggering, digitization of windows of interest, readout, and data transfer to the Belle II data acquisition system are managed by Xilinx Zynq-7000 programmable system on a chip devices.

The Large Area Picosecond PhotoDetector (LAPPD) Collaboration was formed in 2009 to develop large-area photodetectors capable of time resolutions measured in pico-seconds, with accompanying sub-millimeter spatial resolution. During the next three and one-half years the Collaboration developed the LAPPD design of 20 x 20 cm modules with gains greater than $10^7$ and non-uniformity less than $15\%$, time resolution less than 50 psec for single photons and spatial resolution of 700~microns in both lateral dimensions. We describe the R\&D performed to develop large-area micro-channel plate glass substrates, resistive and secondary-emitting coatings, large-area bialkali photocathodes, and RF-capable hermetic packaging. In addition, the Collaboration developed the necessary electronics for large systems capable of precise timing, built up from a custom low-power 15-GigaSample/sec waveform sampling 6-channel integrated circuit and supported by a two-level modular data acquisition system based on Field-Programmable Gate Arrays for local control, data-sparcification, and triggering. We discuss the formation, organization, and technical successes and short-comings of the Collaboration. The Collaboration ended in December 2012 with a transition from R\&D to commercialization.

Searches for radio signatures of ultra-high energy neutrinos and cosmic rays could benefit from improved efficiency by using real-time beamforming or correlation triggering. For missions with power limitations, such as the ANITA-3 Antarctic balloon experiment, full speed high resolution digitization of incoming signals is not practical. To this end, the University of Hawaii has developed the Realtime Independent Three-bit Converter (RITC), a 3-channel, 3-bit, streaming analog-to-digital converter implemented in the IBM-8RF 0.13 um process. RITC is primarily designed to digitize broadband radio signals produced by the Askaryan effect, and thus targets an analog bandwidth of >1 GHz, with a sample-and-hold architecture capable of storing up to 2.6 gigasamples-per-second. An array of flash analog-to-digital converters perform 3-bit conversion of sets of stored samples while acquisition continues elsewhere in the sampling array. A serial interface is provided to access an array of on chip digital-to-analog converters that control the digitization thresholds for each channel as well as the overall sampling rate. Demultiplexed conversion outputs are read out simultaneously for each channel via a set of 36 LVDS links, each running at 650 Mb/s. We briefly describe the design architecture of RITC. Evaluation of the RITC is currently under way, and we will report testing updates as they become available, including prospects for the use of this architecture as the analog half of a novel triggering system for the ANITA-3 ultra-high energy neutrino experiment., Comment: 3 pages, 5 figures

Searches for radio signatures of ultra-high energy neutrinos and cosmic rays could benefit from improved efficiency by using real-time beamforming or correlation triggering. For missions with power limitations, such as the ANITA-3 Antarctic balloon experiment, full speed high resolution digitization of incoming signals is not practical. To this end, the University of Hawaii has developed the Realtime Independent Three-bit Converter (RITC), a 3-channel, 3-bit, streaming analog-to-digital converter implemented in the IBM-8RF 0.13 um process. RITC is primarily designed to digitize broadband radio signals produced by the Askaryan effect, and thus targets an analog bandwidth of >1 GHz, with a sample-and-hold architecture capable of storing up to 2.6 gigasamples-per-second. An array of flash analog-to-digital converters perform 3-bit conversion of sets of stored samples while acquisition continues elsewhere in the sampling array. A serial interface is provided to access an array of on chip digital-to-analog converters that control the digitization thresholds for each channel as well as the overall sampling rate. Demultiplexed conversion outputs are read out simultaneously for each channel via a set of 36 LVDS links, each running at 650 Mb/s. We briefly describe the design architecture of RITC. Evaluation of the RITC is currently under way, and we will report testing updates as they become available, including prospects for the use of this architecture as the analog half of a novel triggering system for the ANITA-3 ultra-high energy neutrino experiment., Comment: 3 pages, 5 figures

The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since z ∼ 1 can help to diagnose the origins of locally observed correlations between SMBH mass and stellar mass. We therefore construct three samples of elliptical galaxies, one at z ∼ 0 and two at 0.7 ≲ z ≲ 2.5, and quantify their relative positions in the MBH−M * plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher-redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of 7 between z ∼ 1 and z ∼ 0. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of ∼20 at z ∼ 2. The result is robust against variation in the high- and low-redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at z ≲ 2, or that selection and measurement biases are both underestimated, and depend on redshift.