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The 26th Midwest Relativity Meeting aims to bring together researchers from across the Midwest and beyond to discuss General Relativity and a broad range of topics in gravitational physics, including classical and quantum gravity, numerical relativity, relativistic astrophysics, cosmology, gravitational waves, and experimental gravity.
 Olakanmi Akinto, Comsats institute of Information Technology
 Natacha Altamirano, Perimeter Institute
 Dimitry Ayzenberg, Montana State University
 Swetha Bhagwat, Syracuse University
 Pablo Bosch, Perimeter Institute
 Alejandro CardenasAvendano, Montana State University
 Shira Chapman, Perimeter Institute
 Katerina Chatziioannou, CITA
 HsinYu Chen, University of Chicago
 AnneSylvie Deutsch, Pennsylvania State University
 Zoheyr Doctor, University of Chicago
 Ariel Edery, Bishop's University
 Joshua Faber, Rochester Institute of Technology
 Maya Fishbach, University of Chicago
 Heather Fong, CITA
 John Friedman, University of WisconsinMilwaukee
 David Garfinkle, Oakland University
 Daniel George, University of Illinois
 Roman Gold, Perimeter Institute
 Elizabeth Gould, Perimeter Institute
 Daniel Guariento, Perimeter Institute
 Lucas Hackl, Pennsylvania State University
 Theodore Halnon, Pennsylvania State University
 Stephen Harnish, Bluffton University
 CarlJohan Haster, CITA
 Robie Hennigar, University of Waterloo
 Matthew Hogan, Wells College
 Florian Hopfmueller, Perimeter Institute
 Uzair Hussain, Memorial University
 Matthew Johnson, Perimeter Institute & York University
 Darsh Kodwani, CITA
 Ikjyot Singh Kohli, York University
 David Kubiznak, Perimeter Institute
 Prayush Kumar, CITA
 Phil Landry, University of Guelph
 Jacob Lange, Rochester Institute of Technology
 Adam Lewis, CITA
 Steve Liebling, Long Island University
 Hyun Lim, Brigham Young University
 Carlos Lousto, Rochester Institute of Technology
 Wayne Lundberg
 Morgan Lynch, University of WisconsinMilwaukee
 Robert Mann, University of Waterloo
 Raissa Mendes, University of Guelph
 James Mertens, Case Western Reserve University
 Vassilios Mewes, Rochester Institute of Technology
 Jonah Miller, Perimeter Institute
 Hugo Marrochio, Perimeter Institute
 Elliot Nelson, Perimeter Institute
 Keith Ng, University of Waterloo
 Alejandro Satz, Pennsylvania State University
 Zachary Silberman, Rochester Institute of Technology
 Alexander Smith, University of Waterloo
 Sotaro Sugishita, Osaka University
 Alexandra Terrana, Perimeter Institute & York University
 David Wenjie Tian, ICNUNAM
 Erickson Tjoa, University of Waterloo
 Alexander Tolish, University of Chicago
 Eric Van Oeveren, University of WisconsinMilwaukee
 Trevor Vincent, CITA
 Shouhong Wang, Indiana University
 ISheng Yang, Perimeter Institute & CITA
 Aaron Zimmerman, CITA
 Peter Zimmerman, University of Arizona
 Yosef Zlochower, Rochester Institute of Technology
 Nosiphiwo Zwane, Perimeter Institute
 Olakanmi Akinto, Comsats institute of Information Technology
 Natacha Altamirano, Perimeter Institute
 Tom Andersen, Keaten House
 Dimitry Ayzenberg, Montana State University
 Swetha Bhagwat, Syracuse University
 David Blair, Michigan State University
 Ssohrab Borhanian, Pennsylvania State University
 Pablo Bosch, Perimeter Institute
 Oleg Boulanov, Laval University
 Alex Buchel, Perimeter Institute
 Alejandro CardenasAvendano, Montana State University
 Shira Chapman, Perimeter Institute
 Katerina Chatziioannou, CITA
 HsinYu Chen, University of Chicago
 Sean Crowe, Pennsylvania State University
 Hristu Culetu, Ovidius University
 Karl Davidson, University of Guelph
 AnneSylvie Deutsch, Pennsylvania State University
 Zoheyr Doctor, University of Chicago
 William East, Perimeter Institute
 Ariel Edery, Bishop's University
 Joshua Faber, Rochester Institute of Technology
 Maya Fishbach, University of Chicago
 Heather Fong, CITA
 John Friedman, University of WisconsinMilwaukee
 David Garfinkle, Oakland University
 Daniel George, University of Illinois
 Roman Gold, Perimeter Institute
 Moctezuma Gonzalez, University of Texas at Austin
 Elizabeth Gould, Perimeter Institute
 Stephen Green, Perimeter Institute
 Lauren Greenspan, Perimeter Institute
 Daniel Guariento, Perimeter Institute
 Lucas Hackl, Pennsylvania State University
 Theodore Halnon, Pennsylvania State University
 Stephen Harnish, Bluffton University
 CarlJohan Haster, CITA
 Robie Hennigar, University of Waterloo
 Matthew Hogan, Wells College
 Florian Hopfmueller, Perimeter Institute
 Uzair Hussain, Memorial University
 Matthew Johnson, Perimeter Institute & York University
 Darsh Kodwani, CITA
 Ikjyot Singh Kohli, York University
 David Kubiznak, Perimeter Institute
 Prayush Kumar, CITA
 Phil Landry, University of Guelph
 Jacob Lange, Rochester Institute of Technology
 Luis Lehner, Perimeter Institute
 Adam Lewis, CITA
 Steve Liebling, Long Island University
 Hyun Lim, Brigham Young University
 Carlos Lousto, Rochester Institute of Technology
 Nicholas Lucas, Pennsylvania State University
 Wayne Lundberg
 Morgan Lynch, University of WisconsinMilwaukee
 Robert Mann, University of Waterloo
 Hugo Marrochio, Perimeter Institute
 Casey McGrath, University of Wisconsin Milwaukee
 Robert McNees, Loyola University Chicago
 Raissa Mendes, University of Guelph
 James Mertens, Case Western Reserve University
 Vassilios Mewes, Rochester Institute of Technology
 Jonah Miller, Perimeter Institute
 Robert Myers, Perimeter Institute
 Elliot Nelson, Perimeter Institute
 Keith Ng, University of Waterloo
 Nestor Oritz, Perimeter Institute
 Richard O'Shaughnessy, Rochester Institute of Technology
 Harald Pfeiffer, CITA
 Alexander Pizzuto, Loyola University Chicago
 Dylan Podkowka, University of Guelph
 Eric Poisson, University of Guelph
 Marcelo Ponce, University of Toronto
 Andrew Reeves, Grand River Regional Cancer Centre
 Monica Rincon Ramirez, Pennsylvania State University
 Gautam Satishchandran, University of Chicago
 Alejandro Satz, Pennsylvania State University
 Erik Schnetter, Perimeter Institute
 Barak Shoshany, Perimeter Institute
 Zachary Silberman, Rochester Institute of Technology
 Barbara Skrzypek, Loyola University Chicago
 Alexander Smith, University of Waterloo
 Rafael Sorkin, Perimeter Institute
 Sotaro Sugishita, Osaka University
 Alexandra Terrana, Perimeter Institute & York University
 David Wenjie Tian, ICNUNAM
 Erickson Tjoa, University of Waterloo
 Alexander Tolish, University of Chicago
 Eric Van Oeveren, University of WisconsinMilwaukee
 Trevor Vincent, CITA
 Robert Wald, University of Chicago
 Shouhong Wang, Indiana University
 Ryan WesternacherSchneider, Perimeter Institute
 ISheng Yang, Perimeter Institute & CITA
 Aaron Zimmerman, CITA
 Peter Zimmerman, University of Arizona
 Yosef Zlochower, Rochester Institute of Technology
 Nosiphiwo Zwane, Perimeter Institute
Thursday, October 13, 2016
Time 
Event 
Location 
3:30 – 3:55pm 
Registration 
Reception 
3:55 – 4:00pm 
Welcome 
Theater 
4:00 – 6:00pm

All talks are 10 minutes + 2 minutes for questions AdS/CFT and Quantum Sotaro Sugishita, Osaka University Shira Chapman, Perimeter Institute *Hugo Marrochio, Perimeter Institute David Kubiznak, Perimeter Institute *Erickson Tjoa, University of Waterloo *Robie Hennigar, University of Waterloo Robert Mann, University of Waterloo *Nosiphiwo Zwane, Perimeter Institute Elliot Nelson, Perimeter Institute Matthew Johnson, Perimeter Institute & York University 
Theater 
Friday, October 14, 2016
Time 
Event 
Location 
9:00 – 10:12am 
All talks are 10 minutes + 2 minutes for questions Numerical GR Yosef Zlochower, Rochester Institute of Technology Carlos Lousto, Rochester Institute of Technology Aaron Zimmerman, CITA *Adam Lewis, CITA Vassilios Mewes, Rochester Institute of Technology Prayush Kumar, CITA 
Theater 
10:12 – 11:06am 
Coffee Break 
Bistro – 1^{st} Floor 
11:06 – 12:30pm 
All talks are 10 minutes + 2 minutes for questions Numerical Methods Joshua Faber, Rochester Institute of Technology *Zachary Silberman, Rochester Institute of Technology *Trevor Vincent, CITA *Hyun Lim, Brigham Young University *Jonah Miller, Perimeter Institute Stephen Harnish, Bluffton University Roman Gold, Perimeter Institute 
Theater 
12:30 12:40pm  Conference Photo  Atrium 
12:40 – 2:00pm 
Lunch 
Bistro – 2^{nd} Floor 
2:00 – 3:36pm 
All talks are 10 minutes + 2 minutes for questions Cosmology *Lucas Hackl, Pennsylvania State University David Wenjie Tian, ICNUNAM *Alexandra Terrana, Perimeter Institute & York University *Elizabeth Gould, Perimeter Institute *James Mertens, Case Western Reserve University *Theodore Halnon, Pennsylvania State University Ikjyot Singh Kohli, York University *AnneSylvie Deutsch, Pennsylvania State University 
Theater 
3:36 – 4:30pm 
Coffee Break 
Bistro – 1^{st} Floor 
4:30 – 6:20pm 
All talks are 10 minutes + 2 minutes for questions GWs/Data Analysis *Heather Fong, CITA CarlJohan Haster, CITA *HsinYu Chen, University of Chicago *Swetha Bhagwat, Syracuse University *Jacob Lange, Rochester Institute of Technology *Eric Van Oeveren, University of WisconsinMilwaukee *Zoheyr Doctor, University of Chicago *Maya Fishbach, University of Chicago Daniel George, University of Illinois 
Theater 
6:20 – 8:30pm 
Wine & Cheese Reception 
Bistro – 2^{nd} Floor 
Saturday, October 15, 2016
Time 
Event 
Location 
9:00 – 10:36am 
All talks are 10 minutes + 2 minutes for questions Mathematical GR David Garfinkle, Oakland University *Alexander Tolish, University of Chicago *Darsh Kodwani, CITA Peter Zimmerman, University of Arizona *Pablo Bosch, Perimeter Institute *Phil Landry, University of Guelph *Uzair Hussain, Memorial University *Florian Hopfmueller, Perimeter Institute 
Theater 
10:36 – 11:06am 
Coffee Break 
Bistro – 1^{st} Floor 
11:06 – 12:42pm 
All talks are 10 minutes + 2 minutes for questions Quantum Gravity/Astrophysics Dimitry Ayzenberg, Montana State University *Alexander Smith, University of Waterloo *Alejandro CardenasAvendano, Montana State University *Natacha Altamirano, Perimeter Institute *Morgan Lynch, University of WisconsinMilwaukee Raissa Mendes, University of Guelph *Olakanmi Akinto, Comsats Institute of Information Technology Keith Ng, University of Waterloo 
Theater 
12:42 – 2:30pm 
Lunch 
Bistro – 1^{st} Floor 
2:30 – 3:30pm 
All talks are 10 minutes + 2 minutes for questions Astrophysics ISheng Yang, Perimeter Institute & CITA John Friedman, University of WisconsinMilwaukee Katerina Chatziioannou, CITA Steve Liebling, Long Island University Shouhong Wang, Indiana University 
Theater 
3:30 – 4:00pm 
Coffee Break 
Bistro – 1^{st} Floor 
4:00 – 5:00pm 
All talks are 10 minutes + 2 minutes for questions Quantum Gravity Daniel Guariento, Perimeter Institute Matthew Hogan, Wells College Alejandro Satz, Pennsylvania State University Ariel Edery, Bishop's University Wayne Lundberg 
Theater 
5:00pm 
Thank you and Goodbye 
Theater 
Olakanmi Akinto, Comsats Institute of Information Technology
Strong Gravity Approach to QCD and General Relativity
A systematic study of a Weyl type of action, which is scale free and quadratic in the curvature, is undertaken. The dynamical breaking of this scale invariance induces general relativity (GR) as an effective long distance limit of the theory. We prove that the corresponding field equations of the theory possess an effective pure Yang  Mills potential, which describes the asymptotic freedom and color confinement properties of QCD. This inevitably leads to the solutions of quantum Yang  Mills existence on R4 (with its characteristic mass gap), and dark matter problems. The inherent Bern  Carrasco  Johansson (BCJ) double  copy and gauge  gravity duality properties of this formulation lead to the solutions of neutrino mass and dark energy problems. This approach provides a strong gravity basis for the unification of quantum Yang  Mills theory (QYMT) with GR.
Natacha Altamirano, Perimeter Institute
Emergent dark fluid from decoherence in quantum interactions
Much effort has been devoted into understanding the quantum mechanical properties of gravitational interactions. Here we explore the recent suggestion that gravitational interactions are a fundamental classical channel that is described by continuous quantum measurements and feedforward (CQMF). Specifically, we investigate the possibility that some properties of our universe, modeled using a FriedmanRobertsonWalker metric, can emerge from CQMF by introducing an underlying quantum system for the dynamical variables, avoiding well known difficulties in trying to quantize the spacetime itself. We show that the quantum decoherence necessary in such a measurement model manifests itself as a dark energy fluid that fills the spacetime and whose equation of state asymptotically oscillates around the value w = −1/3, regardless of the spatial curvature.
Dimitry Ayzenberg, Montana State University
Testing General Relativity with Black Hole Continuum Spectrum Observations:
EinsteindilatonGaussBonnet Gravity and ChernSimons Gravity
Observations of continuum spectra of black holes allow us to study the physics and properties of accretion disks and black holes. These observations have been used to determine the masses and spin angular momenta of black holes, as well as the temperature, evolution, and magnetic field structure of accretion disks. Continuum spectrum observations can also be used, at least in principle, to test General Relativity in the strongfield regime. In this talk I will present our method and results of using the continuum spectrum to test General Relativity and place constraints on modified gravity theories, specifically EinsteindilatonGaussBonnet gravity and ChernSimons gravity.
Swetha Bhagwat, Syracuse University
Spectroscopic analysis of stellar mass blackhole mergers in our local universe with groundbased gravitational wave detectors
Pablo Bosch, Perimeter Institute
Nonlinear evolution and final fate of charged AdS black hole superradiant instability
We describe the full nonlinear development of the superradiant instability for a charged massless scalar field, coupled to general relativity and electromagnetism, in the vicinity of a ReissnerNordstromAdS black hole. The presence of the negative cosmological constant provides a natural context for considering perfectly reflecting boundary conditions and studying the dynamics as the scalar field interacts repeatedly with the black hole.
Alejandro CardenasAvendano, Montana State University
A study for testing the Kerr metric with AGN iron line eclipses:
Recently, two of us have studied iron line reverberation mapping to test black hole candidates, showing that the time information in reverberation mapping can better constrain the Kerr metric than the timeintegrated approach. Motivated by this finding, here we explore the constraining power of another timedependent measurement: an AGN iron line eclipse. An obscuring cloud passes between the AGN and the distant observer, covering different parts of the accretion disk at different times. Similar to the reverberation measurement, an eclipse might help to better identify the relativistic effects affecting the Xray photons. However, this is not what we find. In our study, we employ the JohannsenPsaltis parametrisation, but we argue that our conclusions hold in a large class of nonKerr metrics. We explain our results pointing out an important difference between reverberation and eclipse measurements. (JCAP 1604:054, 2016)
Shira Chapman, Perimeter Institute
Complexity of Formation in Holography  part I
It has recently been conjectured that computational quantum complexity can be computed for a holographic state by evaluating the gravitational action on a region in the bulk of the dual gravitational theory bounded by null surfaces which goes under the name of the WheelerDeWitt patch. We use a set of rules for evaluating the contributions of the null surfaces and joints to compute the action on such a region anchored at the boundary at t = 0 for certain black hole spacetimes. We compare this result to that of two copies of empty AdS. We find that for boundary dimension d > 2 in the limit of large horizon radius the action difference grows linearly as the horizon entropy with proportionality coefficient (d − 2)/d · cot(π/d). For BTZ black holes the action difference is independent of the black hole mass.
Katerina Chatziioannou, CITA
Probing the Internal Composition of Neutron Stars with Gravitational Waves
Gravitational waves from neutron star binaries carry information about the equation of state of supranuclear matter through a parameter called tidal deformability. Its measurability has been assessed in a number of studies, concluding it could provide important information about the equation of state of neutron star matter. In this talk, I will describe a complimentary approach to the problem of equation of state determination, one which focuses on how information from gravitational waves can be translated in ways that could be of direct benefit to nuclear physicists. Specifically, I will talk about what gravitational waves can tell us about the internal composition of neutron stars, information that is directly applicable to equation of state modeling.
HsinYu Chen, University of Chicago
Observational Selection Effects with GroundBased Gravitational Wave Detectors
Groundbased interferometers are not perfectly allsky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean and, as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources’ right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO’s observations and electromagnetic followup. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over 80% of the localization probability, while midlatitudes will access closer to 70%. Facilities located near the two LIGO sites can observe sources closer to their zenith than their analogs in the South, but the average observation will still be no closer than 44◦ from zenith. We also find that observatories in Africa or the South Atlantic will wait systematically longer before they can begin observing compared to the rest of the world, although there is a preference for longitudes near the LIGOs. These effects, along with knowledge of the LIGO antenna pattern, can inform electromagnetic followup activities and optimization, including the possibility of directing observations even before gravitationalwave events occur.
AnneSylvie Deutsch, Pennsylvania State University
Inflation, cosmic variance, and the bispectrum in the squeezed limit
Zoheyr Doctor, University of Chicago
Gravitational Wave Emulation Using Gaussian Process Regression
Parameter estimation (PE) for gravitational wave signals from compact binary coalescences (CBCs) requires reliable template waveforms which span the parameter space. Waveforms from numerical relativity are accurate but computationally expensive, so approximate templates are typically used for PE. These 'approximants', while quick to compute, can introduce systematic errors and bias PE results. We describe a machine learning method for generating CBC waveforms and uncertainties using existing accurate waveforms as a training set. Coefficients of a reduced order waveform model are computed and each treated as arising from a Gaussian process. These coefficients and their uncertainties are then interpolated using Gaussian process regression (GPR). As a proof of concept, we construct a training set of approximant waveforms (rather than NR waveforms) in the twodimensional space of chirp mass and mass ratio and interpolate new waveforms with GPR. We demonstrate that the mismatch between interpolated waveforms and approximants is below the 1% level for an appropriate choice of training set and GPR kernel hyperparameters.
Ariel Edery, Bishop's University
Generating Einstein gravity, cosmological constant and Higgs mass from Restricted Weyl Invariance
Recently, it has been pointed out that dimensionless actions in four dimensional curved spacetime possess a symmetry which goes beyond scale invariance but is smaller than full Weyl invariance. This symmetry was dubbed {\it restricted Weyl invariance}. We show that starting with a restricted Weyl invariant action that includes pure $R^2$ gravity and a Higgs sector with no explicit mass, one can generate the EinsteinHilbert action with cosmological constant and a Higgs mass. The model also contains an extra massless scalar field which couples to the Higgs field (and gravity). If the coupling of this extra scalar field to the Higgs field is negligibly small, this fixes the coefficient of the nonminimal coupling $R\Phi^2$ between the Higgs field and gravity.
Joshua Faber, Rochester Institute of Technology
Multidomain spectral methods for initial data and data compression
Spectral methods solvers are widely used throughout numerical relativity to generate initial data. Here, we compare the performance of multidomain spectral techniques with singledomain versions when applied to the binary black hole problem, for a variety of configurations including differing masses and arbitrary spins. We then discuss the prospect for using multidomain spectral methods as a data compression technique for postprocessing applications, and discuss the potential accuracy that can be achieved for binary black hole simulations.
Maya Fishbach, University of Chicago
Final black hole spins from hierarchical mergers
I will discuss the hierarchical merger model for the formation of stellar mass black holes (such as the binary black holes observable by LIGO). In the hierarchical merger model, each black hole in a black hole binary is the result of a merger of two lesser black holes from a previous generation, and the previous generation's black holes may themselves be merger products of an even earlier generation. I will use the formulas of Hoffman, Barausse & Rezzolla (2016) to show that if black holes form in this hierarchical merger scenario, their spin magnitudes follow a certain probability distribution. This spin distribution can be compared to LIGO spin measurements to constrain the hierarchical merger scenario.
Heather Fong, CITA
Error analysis of numerical gravitational waveforms from coalescing binary black holes
The Advanced Laser Interferometer Gravitationalwave Observatory (Advanced LIGO) has finished a successful first observation run and will commence its second run this summer. Detection of compact object binaries utilizes matchedfiltering, which requires a vast collection of highly accurate gravitational waveforms. This talk will present a set of about 100 new alignedspin binary black hole simulations. I will discuss their properties, including a detailed error analysis, which demonstrates that the numerical waveforms are sufficiently accurate for gravitational wave detection purposes, as well as for parameter estimation purposes.
John Friedman, University of WisconsinMilwaukee
Can magneticfield windup kill the rmode instability of neutron stars?
At second order in perturbation theory, the unstable rmode of a rotating star includes growing differential rotation whose form and growth rate are determined by gravitational radiation reaction. With no magnetic field, the angular velocity of a fluid element grows exponentially until the mode reaches its nonlinear saturation amplitude and remains nonzero after saturation. With a background magnetic field, the differential rotation winds up and amplifies the field, and previous work suggests that the amplification may damp out the instability. A background magnetic field, however, turns the timeindependent perturbations corresponding to adding differential rotation into perturbations whose characteristic frequencies are of order the Alfven frequency. We argue that magnetic field growth stops soon after the mode reaches its saturation amplitude. We show that this is the case for a toy model, where magnetic amplification for small saturation amplitude is too small to damp the rmode. For a more realistic model of a cold, rotating neutron star, an analogous upper limit depends on the assumption that there are no marginally unstable perturbations.
David Garfinkle, Oakland University
A simple estimate of gravitational wave memory in binary black hole systems.
Daniel George, University of Illinois
An inspiralmergerringdown waveform model for compact binaries on eccentric orbits
The detection of compact binaries with significant eccentricity in the sensitivity band of gravitational wave detectors will provide critical insights on the dynamics and formation channels of these events. In order to search for these systems and place constraints on their rates, we present a time domain, inspiralmergerringdown waveform model that describes the gravitational wave emission from compact binaries on orbits with low to moderate values of eccentricity. We use this model to explore the detectability of these events in the context of advanced LIGO.
Roman Gold, Perimeter Institute
Black hole accretion flows as seen by the Event Horizon Telescope
Accreting black holes (BHs) are at the core of relativistic astrophysics as messengers of the strongfield regime of General Relativity that carry complementary information to Gravitational Waves. In particular, the black holes in M87 and Sgr A* constitute prime targets for the Event Horizon Telescope, which among other things aims at imaging the imprint of the black hole (its "shadow") on the surrounding relativistic gas.
I will present results from generalrelativistic, polarized radiative transfer models for the inner accretion flow in Sgr A*. The models use timedependent, global GRMHD simulations of hot accretion flows including standardandnormalevolution (SANE) and magnetically arrested disks (MAD). I present comparisons of these synthetic data sets to the most recent observations with the Event Horizon Telescope and show how the data distinguishes the models and probes the magnetic field structure.
Elizabeth Gould, Perimeter Institute
Observational Constraints of Holographic Cosmology from Planck Data
The holographic cosmology framework expresses inflationary predictions in terms of the observables of a 3D quantum field theory (QFT). It predicts two possible regimes for power spectra of primordial curvature perturbations. The first is well approximated by the standard power law expansion (for strongly coupled QFT), while the second is a new holographic expansion, dual to a weakly coupled QFT in the UV, but strong coupling in the IR. We compare the two regimes against the current cosmological observations and show that they do equally well at l>30, where a holographic perturbative expansion can be trusted. However, the (naive) holographic expansion is disfavored by data at low l's at ~2 sigma level.
Daniel Guariento, Perimeter Institute
Selfgravitating fluid solutions of Shape Dynamics
Shape Dynamics is a 3D conformally invariant theory of gravity which possesses an increasingly large set of solutions in common with General Relativity. Upon close inspection, these solutions behave in surprising ways, so in order to probe the fitness of Shape Dynamics as a viable alternative to General Relativity one must understand increasingly complex solutions, on which to base perturbative studies and numerical analyses. We show that a class of timedependent exact solutions of Shape Dynamics exists from first principles, representing a central inhomogeneity in an evolving cosmological environment. By assuming only a perfect fluid source in a spherically symmetric geometry we show that this fully dynamic nonvacuum solution satisfies in all generality the Hamiltonian structure of Shape Dynamics. The solutions are characterized by shearfree flow of the fluid and admit an interpretation as cosmological black holes.
Lucas Hackl, Pennsylvania State University
Entanglement production in cosmology
Entanglement entropy provides a measure to quantify correlations in a quantum state, for instance of a scalar field representing matter on a cosmological background geometry. In this talk, I will discuss the time evolution of the entanglement entropy during inflation and reheating. I show that instabilities and parametric resonance can lead to a linear growth of the entanglement entropy in generic subsystems.
Theodore Halnon, Pennsylvania State University
Covariance and Quantum Cosmology
In relativity, time is relative between reference frames so we can exclude coordinate independence. However when general relativity is combined with quantum mechanics, the problem is that quantum mechanics requires a time coordinate in order to write an evolution equation for wave functions. One method to study relativity is to interpret the dynamics of a matter field as a clock. We look at an isotropic cosmological model with two matter ingredients. One is given by a scalar field and one by vacuum energy or a cosmological constant. In our systems, there are two matter fields and thus two clock rates. This paper considers two Hamiltonians derived from their respective clock rates. We find semiclassical solutions for these equations and compare the physical predictions that they imply.
Stephen Harnish, Bluffton University
Analog gravity: computational analysis for acoustic metrics
Mathematical analysis of sonic wave simulations from NCSA Blue Waters determines acoustic metrics controlled by pressure and temperature within an LJ lattice. These techniques offer reverse engineering of acoustic metrics for models of analog gravity.
CarlJohan Haster, CITA
Fast and Accurate Inference on Gravitational Waves from Precessing Compact Binaries
After a detection candidate has been observed with gravitational waves, the next task becomes to identify the inference of possible combinations of source parameters. These parameter estimation studies of compact binary gravitational wave events are heavily limited in their flexibility and usefulness by computational cost. Using ROQ (Reduced Order Quadrature) methods it is however possible to bring this cost down by several orders of magnitude, while not sacrificing any accuracy, therefore enabling parameter estimation studies at a completely new level. In this talk, I will showcase the capabilities of the underlying ROQ formalism and give highlights of the parameter estimation studies now within reach.
Robie Hennigar, University of Waterloo
Thermodynamics of hairy black holes in Lovelock gravity
I will discuss the thermodynamics of a class of hairy black holes in Lovelock gravity from the perspective of black hole chemistry. These analytic black hole solutions arise from the conformal coupling of a real scalar field to the dimensionally extended Euler densities and provide an ideal testbed for examining the effects of scalar hair on black hole thermodynamics. Studying the linearized field equations about a maximally symmetric background reveals that the theory is free from ghost and tachyon instabilities provided constraints are enforced on the coupling constants. The black hole solutions display a variety of interesting thermodynamic behaviour including (virtual) triple points, reentrant phase transitions, isolated critical points, and include the newly discovered "superfluid black holes".
Matthew Hogan, Wells College
Diffeomorphism invariant cosmological symmetry in full quantum gravity
This talk summarizes a new proposal to define rigorously a sector of loop quantum gravity at the diffeomorphism invariant level corresponding to homogeneous and isotropic cosmologies, thereby enabling a detailed comparison of results in loop quantum gravity and loop quantum cosmology. The key technical steps we have completed are (a) to formulate conditions for homogeneity and isotropy in a diffeomorphism covariant way on the classical phasespace of general relativity, and (b) to translate these conditions consistently using wellunderstood techniques to loop quantum gravity. We also describe, as a proof of concept, a complete analysis of an analogous embedding of homogeneous and isotropic loop quantum cosmology into the quantum Bianchi I model of Ashtekar and WilsonEwing.
Florian Hopfmueller, Perimeter Institute
The Null Canonical Pairs of Gravity
The symplectic potential of Einstein gravity is integrated on a null hypersurface to obtain the canonical pairs of configuration and momentum variables, without introducing any gauge fixing. Corner degrees of freedom and the connection with boundary terms in the Lagrangian are discussed. Some of the remaining degrees of freedom are pushed to the corner, using diffeomorphisms.
Uzair Hussain, Memorial University
Extreme mass ratio merger and horizon deformation
We study the dynamical spacetime that arises when a small object radially plunges into a large Schwarzschild black hole. We assume that the mass of the small object, \mu, is much smaller than the black hole mass M. Under this assumption we can employ the Zerilli formalism modified to include a source term which arises from the energymomentum tensor of the small object. We solve the Zerilli equation by numerically evolving initial data for various low\ell modes of the spherical harmonics. Then, we ray trace null geodesics of the event horizon after the merger backward in time to extract the geometry of the perturbed event horizon. Further, we take advantage of the axisymmetry of the setup to locate the apparent horizon and its geometry.
Matthew Johnson, Perimeter Institute & York University
Constraining cosmological ultralarge scale structure using numerical relativity
Cosmic inflation, a period of accelerated expansion in the early universe, can give rise to large amplitude ultralarge scale inhomogeneities on distance scales comparable to or larger than the observable universe. The cosmic microwave background (CMB) anisotropy on the largest angular scales is sensitive to such inhomogeneities and can be used to constrain the presence of ultralarge scale structure. I will present the results of simulations in a variety of scenarios that illustrate how numerical relativity can be useful for observational cosmology in determining the history of the very early Universe.
Darsh Kodwani, CITA
Longitudinal gravitational memory
It is well known that gravitational waves leave a permanent displacement between two freefalling masses  a memory effect. We present a similar effect caused by neutrino shells that leads a change in relative velocity between two freely falling masses and the potential detection of this effect using pulsar timing and interferometers (pulsar scintillation in particular).
Ikjyot Singh Kohli, York University
Stochastic Eternal Inflation in Heisenberg Universes
I will discuss the stochastic dynamics and the implications for a minimally coupled scalar field in a Bianchi Type II / Heisenberg universe.
David Kubiznak, Perimeter Institute
On Thermodynamics of Accelerating Black Holes
I will discuss how to formulate consistent thermodynamics for accelerating black holes described by the Cmetric.
Prayush Kumar, CITA
Measuring neutron star tidal deformability with Advanced LIGO with neutron star  black hole binaries
The pioneering discovery of gravitational waves (GW) by Advanced LIGO has ushered us into an era of observational GW astrophysics. Compact binaries remain the primary target sources for GW observation, of which neutron star  black hole (NSBH) binaries form an important subset. GWs from NSBH sources carry signatures of (a) the neutron star's tidal distortion by the companion black hole during inspiral, and (b) its potential tidal disruption near merger. In this talk, I will discuss how well we can measure the leading order tidal effects from individual, as well as populations of, LIGO observations of disruptive NSBH mergers. I will also discuss how our measurements of nontidal parameters can get affected by ignoring tidal effects in LIGO's parameter estimation analyses.
Phil Landry, University of Guelph
Dynamical Tidal Response of a Rotating Neutron Star
A neutron star (NS) subject to a gravitomagnetic tidal field (associated with mass currents) develops internal fluid motions through gravitomagnetic induction; the fluid motions are irrotational, provided the star is nonrotating.
When the NS is allowed to rotate, the tidal field couples to the star's spin; the coupling is tractable in the slowrotation limit. In this case, the fluid motions induced by an external gravitomagnetic field are fully dynamical, even if the tidal field is stationary: interior metric and fluid variables are timedependent, and vary on the timescale of the rotation period. Remarkably, the exterior geometry of the NS remains timeindependent.
Jacob Lange, Rochester Institute of Technology
Comparing Synthetic Gravitational Wave data from Binary Black Hole Coalescence Directly to Numerical Solutions of Einstein’s Equation
We compare synthetic data directly to complete numerical relativity simulations of binary black holes. In doing so, we circumvent adhoc approximations introduced in semianalytical models previously used in gravitational wave parameter estimation and compare the data against the most accurate waveforms including higher modes. In this talk, we focus on the synthetic studies that test potential sources of systematic errors. We also run "endtoend" studies of intrinsically different synthetic sources to show we can recover parameters for different systems.
Adam Lewis, CITA
Fundamental Frequency Extraction from Precessing Eccentric BBH Simulations
Despite considerable interest, the study of eccentric binary black hole inspirals remains highly underdeveloped on both numerical and analytic fronts. We therefore report here on a series of very long (12000M, where M is the total mass of the binary) “generic” fully nonlinear BBH simulations, with initial eccentricities of about 0.1 and 0.2, mass ratios of 5 and 7, primary spin magnitudes of 0.6 and 0.8, and spinseparation inclination angles ranging between 0 and 80 degrees. We use these runs to showcase techniques for extracting the fundamental coordinate frequencies of the motion. These yield new gaugeinsensitive methods for analyticnumeric comparisons. Our techniques also allow for the detection of orbital resonances, which we detect but measure no effect from.
Steve Liebling, Long Island University
Pushing GR's Limits With LIGO's Detections
Hyun Lim, Brigham Young University
A wavelet approach for binary compact object merger
Highly accurate simulations of binary black holes and neutron stars are needed to address a variety of interesting problems in relativistic astrophysics. We present a new method for solving the Einstein equations in the BSSN and CCZ4 formulations using iterated interpolating wavelets. Wavelet coefficients provide a direct measure of the local approximation error for a solution and place collocation points that naturally adapt to features of the solution. Further, they exhibit exponential convergence on unevenly spaced collection points. The parallel implementation of the wavelet simulation framework presented here deviates from conventional practice in combining multithreading with a form of messagedriven computation sometimes referred to as asynchronous multitasking.
Carlos Lousto, Rochester Institute of Technology
Modeling the source of GW150914 and GW151226 with targeted numericalrelativity simulations
The theoretical gravitationalwave signal for merging black holes, as predicted by general relativity, can be computed only by full numerical relativity, because analytic approximations fail near the time of merger. In this talk, we report the modeling of GW150914 and GW151226 with numericalrelativity simulations, using blackhole masses and spins consistent with those inferred from LIGO's measurement. In particular, we employ two independent numericalrelativity codes that use completely different analytical and numerical methods to model the same merging black holes and to compute the emitted gravitational waveform; we find excellent agreement between the waveforms produced by the two independent codes.
Wayne Lundberg
A Comprehensive Theory Scorecard
A broad perspective on theoretical physics is achieved by simply scoring success at addressing various problems. Such problems are generally distinct areas in the ontology of physics research…but each claim to be seeking insight into a “common mathematical foundation.” A concerted search is also motivated by the discovery of Higgs Boson, together with new empirical constraints. The ‘scorecard’ approach interrelates the collected body of results, particularly efforts to explain gravitational anomalies. It is important to diagnose inconsistency of theoretical formulae with those that govern other spacetime scales. Inconsistent formulation frustrates existing theories’ success at explaining anomalous particle, gravitational and cosmological observations. The key is to determine which theory must be reformulated and how! A wellfounded theory applicable across all physical scales results which yields qualitative agreement with all observations.
Morgan Lynch, University of WisconsinMilwaukee
Temperatures of Renormalizable Quantum Field Theories in Curved Spacetime
We compute the temperature registered by an UnruhDeWitt detector coupled to a Hadamard renormalizable quantum field and moving along an arbitrary accelerated trajectory in curved spacetime.
Robert Mann, University of Waterloo
Noisy Quantum Cosmology
Hugo Marrochio, Perimeter Institute
Complexity of Formation in Holography  part II
It has recently been conjectured that computational quantum complexity can be computed for a holographic state by evaluating the gravitational action on a region in the bulk of the dual gravitational theory bounded by null surfaces which goes under the name of the WheelerDeWitt patch. We use a set of rules for evaluating the contributions of the null surfaces and joints to compute the action on such a region anchored at the boundary at t = 0 for certain black hole spacetimes. We compare this result to that of two copies of empty AdS. We find that for boundary dimension d > 2 in the limit of large horizon radius the action difference grows linearly as the horizon entropy with proportionality coefficient (d − 2)/d · cot(π/d). For BTZ black holes the action difference is independent of the black hole mass.
Raissa Mendes, University of Guelph
Testing scalartensor theories with highly compact neutron stars
Scalartensor theories of gravity are extensions of General Relativity including an extra, nonminimally coupled scalar degree of freedom. A wide class of these theories, albeit indistinguishable from GR in the weak field regime, can predict a radically different phenomenology for neutron stars, due to the existence of a nonperturbative, strongfield effect referred to as spontaneous scalarization. This effect is known to occur for theories where the linear effective coupling $\beta$ between the scalar and matter fields is sufficiently negative, and has been strongly constrained by pulsar timing observations. In this talk, I discuss the possibility of testing scalartensor theories in the highly unconstrained region of coupling functions with $\beta>0$, based on the fact that sufficiently compact neutron stars in these theories would be subject to a tachyoniclike instability. I will discuss the results of numerical simulations determining the various endstates of this instability and their observational signatures.
James Mertens, Case Western Reserve University
Deviations from Homogeneity in an Inhomogeneous Universe
It has long been wondered to what extent the observable properties of an inhomogeneous universe will be measurably different from a corresponding FLRW model. Here, we use tools from numerical relativity to study the properties of photons traversing an inhomogeneous universe. We evolve the full, unconstrained Einstein field equations for a spacetime containing dust and vacuum energy in proportions similar to our Universe, with a spectrum of longwavelength density perturbations similar to the observed one. We then integrate the optical scalar equations along paths through this numerical spacetime, with all paths terminating at an observer situated similarly to ourselves, and construct the resulting Hubble diagrams.
Vassilios Mewes, Rochester Institute of Technology
Numerical relativity simulations of tilted BHtorus systems
We present results from threedimensional, numerical relativity simulations of a {\it tilted} black holethick accretion disc system. The simulations are analysed using tracer particles in the disc which are advected with the flow. Such tracers, which we employ in these new simulations for the first time, provide a powerful means to analyse in detail the complex dynamics of tilted black holetorus systems. We show how its use helps to gain insight in the overall dynamics of the system, discussing the origin of the observed black hole precession and the development of a global nonaxisymmetric m=1 mode in the disc. Our threedimensional simulations show the presence of quasiperiodic oscillations (QPOs) in the instantaneous accretion rate, with frequencies in a range compatible with those observed in low mass Xray binaries with either a black hole or a neutron star component. The frequency ratio of the dominant low frequency peak and the first overtone is o1/f∼1.9, a frequency ratio not attainable when modelling the QPOs as pmode oscillations in axisymmetric tori.
Jonah Miller, Perimeter Institute
Simulating the Ejecta of Binary Neutron Star Coalescence at High Resolution
Observational signatures of binary neutron star mergers include gravitational waves and faint supernovalike transients powered by radioactive decay of freshly synthesized heavy elements. We use smoothed particle hydrodynamics, which is well suited for such problems, and adapt the highly scalable 2HOT code to simulate these mergers. Retaining performance while adding new physics provides a unique opportunity to exercise the principles of codesign and for a collaboration between domain and computer scientists.
Elliot Nelson, Perimeter Institute
Quantum Information of the Inflationary Wavefunction
During inflation, the degrees of freedom of metric fluctuations in different regions of space become entangled, and share information that leads to decoherence of quantum fluctuations into classical field perturbations. We apply quantum information tools to study this process and relate the spread of redundant information to the dynamics of the inflationary wave functional, commenting on the role of gravity and on branching of the wave function.
Keith Ng, University of Waterloo
The equivalence principle and QFT: Can a particle detector tell if we live inside a hollow shell?
We show that a particle detector can distinguish the interior of a hollow shell from flat space for switching times much shorter than the lightcrossing time of the shell, even though the local metrics are indistinguishable. This shows that a particle detector can read out information about the nonlocal structure of spacetime even when switched on for scales much shorter than the characteristic scale of the nonlocality.
Alejandro Satz, Pennsylvania State University
Entropy of observable subalgebras and quantum field entanglement
A new perspective on the entanglement entropy of quantum fields restricted to a spatial region can be attained by seeing it as a limiting case of a welldefined and more general quantity, the entropy of a subalgebra of smeared field observables. We introduce this notion and discuss various examples, including the recovery from it of the entanglement entropy of a sphere in Minkowski space.
Zachary Silberman, Rochester Institute of Technology
Generation of Vector Potentials for Numerical Relativity Initial Data
In studies of highly relativistic magnetized accretion flows around black holes, many different numerical codes are employed; while some codes evolve the magnetic field vector B, others evolve the magnetic vector potential A, the two being related by the curl: B=curl(A). Here, we discuss how to generate vector potentials corresponding to specified magnetic fields on staggered grids, a surprisingly difficult task on finite cubic domains. The code we have developed solves this problem in two ways: a direct linear algebra approach and a bruteforce method whose scaling is nearly linear in the number of grid cells. We discuss the success both algorithms have in generating smooth vector potential configurations, how they scale for various problem sizes, and how both may be extended to more complicated cases involving multiple meshrefinement levels.
Alexander Smith, University of Waterloo
Spacetime Topology and Vacuum Entanglement
Questions about the topological structure of our Universe are unanswered by the theory of relativity and are expected to be explained by a full theory of quantum gravity. In this talk, we will analyze how the topology of our Universe influences both vacuum fluctuations and vacuum entanglement. We will see in what ways and to what extent particle detectors are sensitive to the underlying topology of the Universe, and we will discuss how to use them to distinguish universes with identical local geometry but differing global topology. Further, we will see that if the spacetime topology induces a preferred direction, the vacuum entanglement harvesting protocol becomes sensitive to it.
Sotaro Sugishita, Osaka University
Entanglement entropy for free scalar fields in AdS:
We compute entanglement entropy for free massive scalar fields in AdS. The entangling surface is a minimal surface whose boundary is a sphere at the boundary of AdS. We also evaluate 1loop quantum corrections coming from the scalar fields to holographic entanglement entropy. Applying the results, we compute the leading difference of entanglement entropy between two holographic CFTs related by a renormalization group flow triggered by a double trace deformation. This talk is based on arXiv:1608.00305.
Alexandra Terrana, Perimeter Institute & York University
Mapping the Universe with the largescale kinetic SunyaevZel'dovich effect
In this talk, I describe how the kinetic SunyaevZel'dovich (kSZ) effect, cosmic microwave background (CMB) anisotropies induced by the Compton scattering of CMB photons by free electrons undergoing bulk motion, can be a tool for studying the observable Universe on the largest scales. In this regime, the kSZ effect is a census of the CMB dipole observed by free electrons on our past light cone in the postreionzation Universe. Long wavelength modes of the gravitational potential induce a power asymmetry in the cross correlation of the kSZ CMB anisotropies and the electron density field as a function of redshift. We forecast the ability of future experiments to detect this signal, and the possibility of using this signature to reconstruct the 3D gravitational potential on large scales.
David Wenjie Tian, ICNUNAM
The very early Universe in modified gravity
In modified gravities and with respective to the minimal standard model, one can study the gravitational baryogenesis and leptogenesis induced by nonstandard cosmic expansion; investigate hot, warm and cold dark matter as thermal relics of the very early Universe; calculate the primordial abundances of D, T, He3, He4, Li6, Li7, Be7 from the semianalytical approach; and look into hydrogen recombination and the cosmic microwave background. We will take powerlaw f(R) and nonminimally coupled f(R,Tm) gravities as examples to illustrate that, nonstandard behaviors of the very early Universe in different eras exert joint constraints on the viability of modified gravity theories.
Erickson Tjoa, University of Waterloo
Superfluid Black Holes
In this talk I will discuss the recently discovered "superfluid black holes". These are the first example of black holes which exhibit a ``$\lambda$line" phase transition, i.e. a line of second order (continuous) phase transitions. The transition closely resembles those found in condensed matter systems which, in the case of liquid $^4$He marks the normal fluid/superfluid transition. This lambda transition occurs within the context of black hole chemistry for a class of asymptotically antide Sitter hairy black holes in cubic (and higher) order Lovelock gravity where a real scalar field is conformally coupled to gravity. During my talk I will discuss the model, the phase transition, and the necessary conditions a black hole equation of state must satisfy to admit $\lambda$lines.
Alexander Tolish, University of Chicago
The Cosmological Memory Effect:
The "memory effect" is the permanent change in the relative separation of test particles resulting from the passage of gravitational radiation. We investigate the memory effect for a general, spatially flat FLRW cosmology by considering the radiation associated with emission events involving particlelike sources. We find that if the resulting perturbation is decomposed into scalar, vector, and tensor parts, only the tensor part contributes to memory. Furthermore, the tensor contribution to memory depends only on the cosmological scale factor at the source and observation events, not on the detailed expansion history of the universe. In particular, for sources at the same luminosity distance, the memory effect in a spatially flat FLRW spacetime is enhanced over the Minkowski case by a factor of (1+z).
Eric Van Oeveren, University of WisconsinMilwaukee
A Constraint on the Tidal Deformability of Neutron Stars
LIGO will soon detect gravitational waves sourced by the inspiral and merger of binary systems that include neutron stars. These signals will include information about the neutron star equation of state; in particular, the phase evolution will give a constraint on the tidal deformability of neutron stars. We place a theoretical constraint, based on causality, on the tidal deformability and estimate the resulting effect on the gravitational waves from a black holeneutron star binary.
Trevor Vincent, CITA
Computing Initial Data with Discontinuous Galerkin Methods
Discontinuous Galerkin (DG) finite element methods have been used to solve hyperbolic PDEs in relativistic simulations and offer advantages over traditional discretization methods. Comparatively little attention has been given towards using the DG method to solve the elliptic PDEs arising from the Einstein initial data equations. We describe how the DG method can be used to create a parallel, adaptive solver for initial data. We discuss the current state of the dG code we are developing.
Shouhong Wang, Indiana University
Law of gravity, dark matter and dark energy
In this talk, we demonstrate that the presence of dark matter and dark energy requires that the variation of the EinsteinHilbert action be taken under energymomentum conservation constraint. This gives rise to a new set of field equations, altering the Einstein equations with a new term analytically derived from the constraints. Then we show that with the gravitational field equations, gravity behaves like the Einstein gravity in the solar system, and it has more attraction in the galactic scale (dark matter), and it becomes repulsive over very large scale (dark energy).
ISheng Yang, Perimeter Institute & CITA
Gravitational rotation of polarization from pulsar binaries.
Aaron Zimmerman, CITA
Extracting the redshift factor in binary black hole simulations
The redshift factor of a black hole is an invariant quantity of fundamental interest in PN and selfforce descriptions of circular binaries. We have implemented a novel method for extracting the redshift factor in simulations, confirming a conjectured relationship between it and the surface gravity of a black hole. This redshift factor allows for an array of new comparisons between analytical approximations and numerical simulations, and it also allows us to test a generalization of the first law of black hole mechanics to binaries. I will present our method and initial comparisons between analytics and numerics.
Peter Zimmerman, University of Arizona
Horizon Instability of Extremal Black Holes
Aretakis's discovery of a horizon instability of extremal black holes came as something of a surprise given earlier proofs that individual frequency modes are bounded. Is this kind of instability invisible to frequencydomain analysis? The answer is no: We show that the horizon instability of the Kerr black hole can be recovered in a mode analysis as a branch point at the horizon frequency. We use the mode approach to generalize to nonaxisymmetric perturbations, finding an enhanced growth rate. In the electromagnetic and gravitational cases, the field strength and curvature exhibit unbounded growth in time. Finally, by studying charged scalar perturbations of the extremal Reissner–Nordströ m solution, we connect the enhanced growth to the existence of a superradiant bound.
Yosef Zlochower, Rochester Institute of Technology
PunctureBased Evolutions of Highly Spinning BlackHole Binaries
We recently developed a code for solving the 3+1 system of constraints for highlyspinning blackhole binary initial data in the puncture formalism. Here we explore how different choices of gauge can be used to efficiently evolve binaries with near maximal spins.
Nosiphiwo Zwane, Perimeter Institute
Cosmological test of Everpresent Lambda
Everpresent Lambda is a cosmological scenario inspired by the causal set approach to quantum gravity, which predicts that the observed "cosmological constant" fluctuates between positive and negative values with a vanishing mean. This implies that the "cosmological constant" is a stochastic function of cosmic time, with a standard deviation comparable to the critical density of the universe at any epoch. By exploring the space of cosmological parameters and stochastic realizations of dark energy via Monte Carlo Markov chains, we show that Everpresent Lambda can fit cosmological observations as well as the standard LCDM model. Furthermore, it can potentially ease some high redshift tensions with CDM model, such as the Baryonic Acoustic Oscillations (BAO) in Lyman forest at z 2~3, the ultramassive black holes at z ~ 7, and the primordial Lithium abundance.
Scientific Organizers:
 William East, Perimeter Institute
 Stephen Green, Perimeter Institute
 Luis Lehner, Perimeter Institute
 Nestor Ortiz, Perimeter Institute