@article{10738, abstract = {We prove an adiabatic theorem for the Landau–Pekar equations. This allows us to derive new results on the accuracy of their use as effective equations for the time evolution generated by the Fröhlich Hamiltonian with large coupling constant α. In particular, we show that the time evolution of Pekar product states with coherent phonon field and the electron being trapped by the phonons is well approximated by the Landau–Pekar equations until times short compared to α2.}, author = {Leopold, Nikolai K and Rademacher, Simone Anna Elvira and Schlein, Benjamin and Seiringer, Robert}, issn = {1948-206X}, journal = {Analysis and PDE}, number = {7}, pages = {2079--2100}, publisher = {Mathematical Sciences Publishers}, title = {{ The Landau–Pekar equations: Adiabatic theorem and accuracy}}, doi = {10.2140/APDE.2021.14.2079}, volume = {14}, year = {2021}, } @unpublished{10762, abstract = {Methods inspired from machine learning have recently attracted great interest in the computational study of quantum many-particle systems. So far, however, it has proven challenging to deal with microscopic models in which the total number of particles is not conserved. To address this issue, we propose a new variant of neural network states, which we term neural coherent states. Taking the Fröhlich impurity model as a case study, we show that neural coherent states can learn the ground state of non-additive systems very well. In particular, we observe substantial improvement over the standard coherent state estimates in the most challenging intermediate coupling regime. Our approach is generic and does not assume specific details of the system, suggesting wide applications.}, author = {Rzadkowski, Wojciech and Lemeshko, Mikhail and Mentink, Johan H.}, booktitle = {arXiv}, pages = {2105.15193}, title = {{Artificial neural network states for non-additive systems}}, doi = {10.48550/arXiv.2105.15193}, year = {2021}, } @unpublished{10803, abstract = {Given the abundance of applications of ranking in recent years, addressing fairness concerns around automated ranking systems becomes necessary for increasing the trust among end-users. Previous work on fair ranking has mostly focused on application-specific fairness notions, often tailored to online advertising, and it rarely considers learning as part of the process. In this work, we show how to transfer numerous fairness notions from binary classification to a learning to rank setting. Our formalism allows us to design methods for incorporating fairness objectives with provable generalization guarantees. An extensive experimental evaluation shows that our method can improve ranking fairness substantially with no or only little loss of model quality.}, author = {Konstantinov, Nikola H and Lampert, Christoph}, booktitle = {arXiv}, title = {{Fairness through regularization for learning to rank}}, doi = {10.48550/arXiv.2102.05996}, year = {2021}, } @article{10806, abstract = {Ligands are a fundamental part of nanocrystals. They control and direct nanocrystal syntheses and provide colloidal stability. Bound ligands also affect the nanocrystals’ chemical reactivity and electronic structure. Surface chemistry is thus crucial to understand nanocrystal properties and functionality. Here, we investigate the synthesis of metal oxide nanocrystals (CeO2-x, ZnO, and NiO) from metal nitrate precursors, in the presence of oleylamine ligands. Surprisingly, the nanocrystals are capped exclusively with a fatty acid instead of oleylamine. Analysis of the reaction mixtures with nuclear magnetic resonance spectroscopy revealed several reaction byproducts and intermediates that are common to the decomposition of Ce, Zn, Ni, and Zr nitrate precursors. Our evidence supports the oxidation of alkylamine and formation of a carboxylic acid, thus unraveling this counterintuitive surface chemistry.}, author = {Calcabrini, Mariano and Van den Eynden, Dietger and Sanchez Ribot, Sergi and Pokratath, Rohan and Llorca, Jordi and De Roo, Jonathan and Ibáñez, Maria}, issn = {2691-3704}, journal = {JACS Au}, keywords = {general medicine}, number = {11}, pages = {1898--1903}, publisher = {American Chemical Society}, title = {{Ligand conversion in nanocrystal synthesis: The oxidation of alkylamines to fatty acids by nitrate}}, doi = {10.1021/jacsau.1c00349}, volume = {1}, year = {2021}, } @article{10809, abstract = {Thermoelectric materials are engines that convert heat into an electrical current. Intuitively, the efficiency of this process depends on how many electrons (charge carriers) can move and how easily they do so, how much energy those moving electrons transport, and how easily the temperature gradient is maintained. In terms of material properties, an excellent thermoelectric material requires a high electrical conductivity σ, a high Seebeck coefficient S (a measure of the induced thermoelectric voltage as a function of temperature gradient), and a low thermal conductivity κ. The challenge is that these three properties are strongly interrelated in a conflicting manner (1). On page 722 of this issue, Roychowdhury et al. (2) have found a way to partially break these ties in silver antimony telluride (AgSbTe2) with the addition of cadmium (Cd) cations, which increase the ordering in this inherently disordered thermoelectric material.}, author = {Liu, Yu and Ibáñez, Maria}, issn = {1095-9203}, journal = {Science}, keywords = {multidisciplinary}, number = {6530}, pages = {678--679}, publisher = {American Association for the Advancement of Science}, title = {{Tidying up the mess}}, doi = {10.1126/science.abg0886}, volume = {371}, year = {2021}, } @article{17384, abstract = {Basket weaving is a traditional craft for creating curved surfaces as an interwoven array of thin, flexible, and initially straight ribbons. The three-dimensional shape of a woven structure emerges through a complex interplay of the elastic bending behavior of the ribbons and the contact forces at their crossings. Curvature can be injected by carefully placing topological singularities in the otherwise regular weaving pattern. However, shape control through topology is highly non-trivial and inherently discrete, which severely limits the range of attainable woven geometries. Here, we demonstrate how to construct arbitrary smooth free-form surface geometries by weaving carefully optimized curved ribbons. We present an optimization-based approach to solving the inverse design problem for such woven structures. Our algorithm computes the ribbons' planar geometry such that their interwoven assembly closely approximates a given target design surface in equilibrium. We systematically validate our approach through a series of physical prototypes to show a broad range of new woven geometries that is not achievable by existing methods. We anticipate our computational approach to significantly enhance the capabilities for the design of new woven structures. Facilitated by modern digital fabrication technology, we see potential applications in material science, bio- and mechanical engineering, art, design, and architecture.}, author = {Ren, Yingying and Panetta, Julian and Chen, Tian and Isvoranu, Florin and Poincloux, Samuel and Brandt, Christopher and Martin, Alison and Pauly, Mark}, issn = {1557-7368}, journal = {ACM Transactions on Graphics}, number = {4}, pages = {1--15}, publisher = {Association for Computing Machinery}, title = {{3D weaving with curved ribbons}}, doi = {10.1145/3450626.3459788}, volume = {40}, year = {2021}, } @article{17422, abstract = {Inspired by motion patterns of some commercially available mobile robots, we investigate the power of robots that move forward in straight lines until colliding with an environment boundary, at which point they can rotate in place and move forward again; we visualize this as the robot “bouncing” off boundaries. We define bounce rules governing how the robot should reorient after reaching a boundary, such as reorienting relative to its heading prior to collision, or relative to the normal of the boundary. We then generate plans as sequences of rules, using the bounce visibility graph generated from a polygonal environment definition, while assuming we have unavoidable non-determinism in our actuation. Our planner can be queried to determine the feasibility of tasks such as reaching goal sets and patrolling (repeatedly visiting a sequence of goals). If the task is found feasible, the planner provides a sequence of non-deterministic interaction rules, which also provide information on how precisely the robot must execute the plan to succeed. We also show how to compute stable cyclic trajectories and use these to limit uncertainty in the robot’s position. }, author = {Nilles, Alexandra Q and Ren, Yingying and Becerra, Israel and LaValle, Steven M}, issn = {1741-3176}, journal = {The International Journal of Robotics Research}, number = {10-11}, pages = {1196--1211}, publisher = {SAGE Publications}, title = {{A visibility-based approach to computing non-deterministic bouncing strategies}}, doi = {10.1177/0278364921992788}, volume = {40}, year = {2021}, } @inproceedings{17505, abstract = {Given the central role that C continues to play in systems software, and the difficulty of writing safe and correct C code, it remains a grand challenge to develop effective formal methods for verifying C programs. In this paper, we propose a new approach to this problem: a type system we call RefinedC, which combines ownership types (for modular reasoning about shared state and concurrency) with refinement types (for encoding precise invariants on C data types and Hoare-style specifications for C functions). RefinedC is both automated (requiring minimal user intervention) and foundational (producing a proof of program correctness in Coq), while at the same time handling a range of low-level programming idioms such as pointer arithmetic. In particular, following the approach of RustBelt, the soundness of the RefinedC type system is justified semantically by interpretation into the Coq-based Iris framework for higher-order concurrent separation logic. However, the typing rules of RefinedC are also designed to be encodable in a new “separation logic programming” language we call Lithium. By restricting to a carefully chosen (yet expressive) fragment of separation logic, Lithium supports predictable, automatic, goal-directed proof search without backtracking. We demonstrate the effectiveness of RefinedC on a range of representative examples of C code.}, author = {Sammler, Michael Joachim and Lepigre, Rodolphe and Krebbers, Robbert and Memarian, Kayvan and Dreyer, Derek and Garg, Deepak}, booktitle = {Proceedings of the 42nd ACM SIGPLAN International Conference on Programming Language Design and Implementation}, location = {virtual}, pages = {158--174}, publisher = {Association for Computing Machinery}, title = {{RefinedC: Automating the foundational verification of C code with refined ownership types}}, doi = {10.1145/3453483.3454036}, year = {2021}, } @article{17508, abstract = {This paper presents the ESA Voyage 2050 White Paper for a concept of TeraHertz Exploration and Zooming-in for Astrophysics (THEZA). It addresses the science case and some implementation issues of a space-borne radio interferometric system for ultra-sharp imaging of celestial radio sources at the level of angular resolution down to (sub-) microarcseconds. THEZA focuses at millimetre and sub-millimetre wavelengths (frequencies above 300 GHz), but allows for science operations at longer wavelengths too. The THEZA concept science rationale is focused on the physics of spacetime in the vicinity of supermassive black holes as the leading science driver. The main aim of the concept is to facilitate a major leap by providing researchers with orders of magnitude improvements in the resolution and dynamic range in direct imaging studies of the most exotic objects in the Universe, black holes. The concept will open up a sizeable range of hitherto unreachable parameters of observational astrophysics. It unifies two major lines of development of space-borne radio astronomy of the past decades: Space VLBI (Very Long Baseline Interferometry) and mm- and sub-mm astrophysical studies with “single dish” instruments. It also builds upon the recent success of the Earth-based Event Horizon Telescope (EHT) – the first-ever direct image of a shadow of the super-massive black hole in the centre of the galaxy M87. As an amalgam of these three major areas of modern observational astrophysics, THEZA aims at facilitating a breakthrough in high-resolution high image quality studies in the millimetre and sub-millimetre domain of the electromagnetic spectrum.}, author = {Gurvits, Leonid I. and Paragi, Zsolt and Casasola, Viviana and Conway, John and Davelaar, Jordy and Falcke, Heino and Fender, Rob and Frey, Sándor and Fromm, Christian M. and Miró, Cristina García and Garrett, Michael A. and Giroletti, Marcello and Goddi, Ciriaco and Gómez, José-Luis and van der Gucht, Jeffrey and Guirado, José Carlos and Haiman, Zoltán and Helmich, Frank and Humphreys, Elizabeth and Impellizzeri, Violette and Kramer, Michael and Lindqvist, Michael and Linz, Hendrik and Liuzzo, Elisabetta and Lobanov, Andrei P. and Mizuno, Yosuke and Rezzolla, Luciano and Roelofs, Freek and Ros, Eduardo and Rygl, Kazi L.J. and Savolainen, Tuomas and Schuster, Karl and Venturi, Tiziana and Wiedner, Martina C. and Zensus, J. Anton}, issn = {0922-6435}, journal = {Experimental Astronomy}, number = {3}, pages = {559--594}, publisher = {Springer Science and Business Media LLC}, title = {{THEZA: TeraHertz exploration and zooming-in for astrophysics}}, doi = {10.1007/s10686-021-09714-y}, volume = {51}, year = {2021}, } @article{17509, abstract = {The recently discovered gravitational wave sources GW190521 and GW190814 have shown evidence of BH mergers with masses and spins outside of the range expected from isolated stellar evolution. These merging objects could have undergone previous mergers. Such hierarchical mergers are predicted to be frequent in active galactic nuclei (AGNs) disks, where binaries form and evolve efficiently by dynamical interactions and gaseous dissipation. Here we compare the properties of these observed events to the theoretical models of mergers in AGN disks, which are obtained by performing one-dimensional N-body simulations combined with semi-analytical prescriptions. The high BH masses in GW190521 are consistent with mergers of high-generation (high-g) BHs where the initial progenitor stars had high metallicity, 2g BHs if the original progenitors were metal-poor, or 1g BHs that had gained mass via super-Eddington accretion. Other measured properties related to spin parameters in GW190521 are also consistent with mergers in AGN disks. Furthermore, mergers in the lower mass gap or those with low mass ratio as found in GW190814 and GW190412 are also reproduced by mergers of 2g–1g or 1g–1g objects with significant accretion in AGN disks. Finally, due to gas accretion, the massive neutron star merger reported in GW190425 can be produced in an AGN disk.}, author = {Tagawa, Hiromichi and Kocsis, Bence and Haiman, Zoltán and Bartos, Imre and Omukai, Kazuyuki and Samsing, Johan}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, publisher = {American Astronomical Society}, title = {{Mass-gap mergers in active galactic nuclei}}, doi = {10.3847/1538-4357/abd555}, volume = {908}, year = {2021}, } @article{17515, abstract = {The disks of active galactic nuclei (AGNs) have emerged as a rich environment for the evolution of stars and their compact remnants. The very dense medium favors rapid accretion, while torques and migration traps enhance binary formation and mergers. Both long and short gamma-ray bursts are hence expected. We show that AGN disks constitute an ideal environment for another interesting phenomenon: the accretion-induced collapse (AIC) of neutron stars (NSs) to black holes (BHs). Rapid accretion in the dense disks can cause NSs to grow to the point of exceeding the maximum mass allowed by their equation of state. General relativistic magnetohydrodynamical simulations have shown that electromagnetic signatures are expected if the NS is surrounded by a minidisk prior to collapse, which then rapidly accretes onto the BH, and/or if the NS is highly magnetized, from reconnection of the magnetosphere during collapse. Here we compute the rates of AICs and their locations within the disks for both isolated NSs and for (initially stable) NSs formed from NS-NS mergers. We find that the global AIC rates are ∼0.07–20 Gpc−3 yr−1, and we discuss their observable prospects and signatures as they emerge from the dense disk environments.}, author = {Perna, Rosalba and Tagawa, Hiromichi and Haiman, Zoltán and Bartos, Imre}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, publisher = {American Astronomical Society}, title = {{Accretion-induced collapse of neutron stars in the disks of active galactic nuclei}}, doi = {10.3847/1538-4357/abfdb4}, volume = {915}, year = {2021}, } @article{17516, abstract = {We study the effect of baryonic processes on weak lensing (WL) observables with a suite of mock WL maps, the κTNG, based on the cosmological hydrodynamic simulations IllustrisTNG. We quantify the baryonic effects on the WL angular power spectrum, one-point probability distribution function (PDF), and number counts of peaks and minima. We also show the redshift evolution of the effects, which is a key to distinguish the effect of baryons from fundamental physics such as dark energy, dark matter, and massive neutrinos. We find that baryonic processes reduce the small-scale power, suppress the tails of the PDF, peak and minimum counts, and change the total number of peaks and minima. We compare our results to existing semi-analytical models and hydrodynamic simulations, and discuss the source of discrepancies. The κTNG suite includes 10 000 realizations of $5 \times 5 \, \mathrm{deg}^2$ maps for 40 source redshifts up to zs = 2.6, well covering the range of interest for existing and upcoming WL surveys. We also produce the κTNG-Dark suite of maps, generated based on the corresponding dark matter-only IllustrisTNG simulations. Our mock maps are not only suitable for developing analytical models that incorporate the effect of baryons, but also particularly useful for studies that rely on mass maps, such as non-Gaussian statistics and machine learning with convolutional neural networks. The suite of mock maps is publicly available at Columbia Lensing (http://columbialensing.org).}, author = {Osato, Ken and Liu, Jia and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {5593--5602}, publisher = {Oxford University Press}, title = {{κTNG: effect of baryonic processes on weak lensing with IllustrisTNG simulations}}, doi = {10.1093/mnras/stab395}, volume = {502}, year = {2021}, } @article{17525, abstract = {Since the very beginning of astronomy the location of objects on the sky has been a fundamental observational quantity that has been taken for granted. While precise two dimensional positional information is easy to obtain for observations in the electromagnetic spectrum, the positional accuracy of current and near future gravitational wave detectors is limited to between tens and hundreds of square degrees, which makes it extremely challenging to identify the host galaxies of gravitational wave events or to detect any electromagnetic counterparts. Gravitational wave observations provide information on source properties that is complementary to the information in any associated electromagnetic emission. Observing systems with multiple messengers thus has scientific potential much greater than the sum of its parts. A gravitational wave detector with higher angular resolution would significantly increase the prospects for finding the hosts of gravitational wave sources and triggering a multi-messenger follow-up campaign. An observatory with arcminute precision or better could be realised within the Voyage 2050 programme by creating a large baseline interferometer array in space and would have transformative scientific potential. Precise positional information of standard sirens would enable precision measurements of cosmological parameters and offer new insights on structure formation; a high angular resolution gravitational wave observatory would allow the detection of a stochastic background and resolution of the anisotropies within it; it would also allow the study of accretion processes around black holes; and it would have tremendous potential for tests of modified gravity and the discovery of physics beyond the Standard Model.}, author = {Baker, John and Baker, Tessa and Carbone, Carmelita and Congedo, Giuseppe and Contaldi, Carlo and Dvorkin, Irina and Gair, Jonathan and Haiman, Zoltán and Mota, David F. and Renzini, Arianna and Buis, Ernst-Jan and Cusin, Giulia and Ezquiaga, Jose Maria and Mueller, Guido and Pieroni, Mauro and Quenby, John and Ricciardone, Angelo and Saltas, Ippocratis D. and Shao, Lijing and Tamanini, Nicola and Tasinato, Gianmassimo and Zumalacárregui, Miguel}, issn = {0922-6435}, journal = {Experimental Astronomy}, number = {3}, pages = {1441--1470}, publisher = {Springer Science and Business Media LLC}, title = {{High angular resolution gravitational wave astronomy}}, doi = {10.1007/s10686-021-09712-0}, volume = {51}, year = {2021}, } @article{17534, abstract = {We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to μ-Hz frequency range. By the 2040s, the μ-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a μ-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.}, author = {Sesana, Alberto and Korsakova, Natalia and Sedda, Manuel Arca and Baibhav, Vishal and Barausse, Enrico and Barke, Simon and Berti, Emanuele and Bonetti, Matteo and Capelo, Pedro R. and Caprini, Chiara and Garcia-Bellido, Juan and Haiman, Zoltán and Jani, Karan and Jennrich, Oliver and Johansson, Peter H. and Khan, Fazeel Mahmood and Korol, Valeriya and Lamberts, Astrid and Lupi, Alessandro and Mangiagli, Alberto and Mayer, Lucio and Nardini, Germano and Pacucci, Fabio and Petiteau, Antoine and Raccanelli, Alvise and Rajendran, Surjeet and Regan, John and Shao, Lijing and Spallicci, Alessandro and Tamanini, Nicola and Volonteri, Marta and Warburton, Niels and Wong, Kaze and Zumalacarregui, Miguel}, issn = {0922-6435}, journal = {Experimental Astronomy}, number = {3}, pages = {1333--1383}, publisher = {Springer Science and Business Media LLC}, title = {{Unveiling the gravitational universe at μ-Hz frequencies}}, doi = {10.1007/s10686-021-09709-9}, volume = {51}, year = {2021}, } @article{17574, abstract = {As weak lensing surveys are becoming deeper and cover larger areas, information will be available on small angular scales down to the arcmin level. To extract this extra information, accurate modelling of baryonic effects is necessary. In this work, we adopt a baryonic correction model, which includes gas both bound inside and ejected from dark matter (DM) haloes, a central galaxy, and changes in the DM profile induced by baryons. We use this model to incorporate baryons into a large suite of DM-only N-body simulations, covering a grid of 75 cosmologies in the Ωm–σ8 parameter space. We investigate how baryons affect Gaussian and non-Gaussian weak lensing statistics and the cosmological parameter inferences from these statistics. Our results show that marginalizing over baryonic parameters degrades the constraints in Ωm–σ8 space by a factor of 2–5 compared to those with baryonic parameters fixed. We also find that combining the lensing power spectrum and peak counts can break the degeneracy between cosmological and baryonic parameters and mitigate the impact of the uncertainty in baryonic physics.}, author = {Lu, Tianhuan and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {3406--3417}, publisher = {Oxford University Press}, title = {{The impact of baryons on cosmological inference from weak lensing statistics}}, doi = {10.1093/mnras/stab1978}, volume = {506}, year = {2021}, } @article{17577, abstract = {The Legacy Survey of Space and Time (LSST) by the Vera C. Rubin Observatory is expected to discover tens of millions of quasars. A significant fraction of these could be powered by coalescing massive black hole (MBH) binaries, since many quasars are believed to be triggered by mergers. We show that under plausible assumptions about the luminosity functions, lifetimes, and binary fractions of quasars, we expect the full LSST quasar catalogue to contain between 20 and 100 million compact MBH binaries with masses M = 105–9M⊙, redshifts z = 0–6, and orbital periods P = 1–70 d. Their light-curves are expected to be distinctly periodic, which can be confidently distinguished from stochastic red-noise variability, because LSST will cover dozens, or even hundreds of cycles. A very small subset of 10–150 ultracompact (P ≲ 1 d) binary quasars among these will, over ∼5–15 yr, evolve into the mHz gravitational-wave frequency band and can be detected by LISA. They can therefore be regarded as ‘LISA verification binaries’, analogous to short-period Galactic compact-object binaries. The practical question is how to find these handful of ‘needles in the haystack’ among the large number of quasars: this will likely require a tailored co-adding analysis optimized for this purpose.}, author = {Xin, Chengcheng and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {2408--2417}, publisher = {Oxford University Press}, title = {{Ultra-short-period massive black hole binary candidates in LSST as LISA ‘verification binaries’}}, doi = {10.1093/mnras/stab1856}, volume = {506}, year = {2021}, } @article{17578, abstract = {If primordial black holes (PBHs) seeded the supermassive black holes (SMBHs) at the centers of high-redshift quasars, then the gas surrounding these black holes may reveal nucleosynthetic clues to their primordial origins. We present predictions of altered primordial abundances around PBHs massive enough to seed SMBHs at 𝑧≈6–7.5. We find that if PBHs with initial masses of ∼105  M⊙ are responsible for such SMBHs, they may produce primordial deuterium and Helium fractions enhanced by ≥10%, and lithium abundance depleted by ≥10%, at distances of up to ≈ a comoving kiloparsec away from the black hole after decoupling. We estimate that ∼108  M⊙ of gas is enhanced (or depleted) by at least one percent. Evidence of these modified primordial deuterium, helium, and lithium abundances could still be present if this circum-PBH gas remains unaccreted by the SMBH and in or near the host galaxies of high-redshift quasars. Measuring the abundance anomalies will be challenging, but could offer a novel way to reveal the primordial origin of such SMBH seeds.}, author = {Sanderbeck, Phoebe Upton and Bird, Simeon and Haiman, Zoltán}, issn = {2470-0010}, journal = {Physical Review D}, number = {10}, publisher = {American Physical Society}, title = {{Nucleosynthetic signatures of primordial origin around supermassive black holes}}, doi = {10.1103/physrevd.104.103022}, volume = {104}, year = {2021}, } @article{17583, abstract = {The astrophysical origin of gravitational wave transients is a timely open question in the wake of discoveries by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo. In active galactic nuclei (AGNs), binaries form and evolve efficiently by interaction with a dense population of stars and the gaseous AGN disk. Previous studies have shown that stellar-mass black hole (BH) mergers in such environments can explain the merger rate and the number of suspected hierarchical mergers observed by LIGO/Virgo. The binary eccentricity distribution can provide further information to distinguish between astrophysical models. Here we derive the eccentricity distribution of BH mergers in AGN disks. We find that eccentricity is mainly due to binary–single (BS) interactions, which lead to most BH mergers in AGN disks having a significant eccentricity at 0.01 Hz, detectable by the Laser Interferometer Space Antenna. If BS interactions occur in isotropic-3D directions, then 8%–30% of the mergers in AGN disks will have eccentricities at 10 Hz above e10 Hz ≳ 0.03, detectable by LIGO/Virgo/Kamioka Gravitational Wave Detector, while 5%–17% of mergers have e10 Hz ≥ 0.3. On the other hand, if BS interactions are confined to the AGN–disk plane due to torques from the disk, with 1–20 intermediate binary states during each interaction, or if BHs can migrate to ≲ 10−3 pc from the central supermassive BH, then 10%–70% of the mergers will be highly eccentric (e10 Hz ≥ 0.3), consistent with the possible high eccentricity in GW190521.}, author = {Tagawa, Hiromichi and Kocsis, Bence and Haiman, Zoltán and Bartos, Imre and Omukai, Kazuyuki and Samsing, Johan}, issn = {2041-8205}, journal = {The Astrophysical Journal Letters}, number = {1}, publisher = {American Astronomical Society}, title = {{Eccentric black hole mergers in active galactic nuclei}}, doi = {10.3847/2041-8213/abd4d3}, volume = {907}, year = {2021}, } @article{17585, abstract = {Recent gravitational wave (GW) observations by LIGO/Virgo show evidence for hierarchical mergers, where the merging BHs are the remnants of previous BH merger events. These events may carry important clues about the astrophysical host environments of the GW sources. In this paper, we present the distributions of the effective spin parameter (χeff), the precession spin parameter (χp), and the chirp mass (mchirp) expected in hierarchical mergers. Under a wide range of assumptions, hierarchical mergers produce (i) a monotonic increase of the average of the typical total spin for merging binaries, which we characterize with χ¯typ≡(χ2eff+χ2p)1/2¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯, up to roughly the maximum mchirp among first-generation (1g) BHs, and (ii) a plateau at χ¯typ∼0.6 at higher mchirp. We suggest that the maximum mass and typical spin magnitudes for 1g BHs can be estimated from χ¯typ as a function of mchirp. The GW data observed in LIGO/Virgo O1--O3a prefers an increase in χ¯typ at low mchirp, which is consistent with the growth of the BH spin magnitude by hierarchical mergers, at ∼2σ confidence. A Bayesian analysis suggests that 1g BHs have the maximum mass of ∼15--30M⊙ if the majority of mergers are of high-generation BHs (not among 1g-1g BHs), which is consistent with mergers in active galactic nucleus disks and/or nuclear star clusters, while if mergers mainly originate from globular clusters, 1g BHs are favored to have non-zero spin magnitudes of ∼0.3. We also forecast that signatures for hierarchical mergers in the χ¯typ distribution can be confidently recovered once the number of GW events increases to ≳O(100).}, author = {Tagawa, Hiromichi and Haiman, Zoltán and Bartos, Imre and Kocsis, Bence and Omukai, Kazuyuki}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {3362--3380}, publisher = {Oxford University Press}, title = {{Signatures of hierarchical mergers in black hole spin and mass distribution}}, doi = {10.1093/mnras/stab2315}, volume = {507}, year = {2021}, } @article{17586, abstract = {Variable active galactic nuclei showing periodic light curves have been proposed as massive black hole binary (MBHB) candidates. In such scenarios, the periodicity can be due to relativistic Doppler-boosting of the emitted light. This hypothesis can be tested through the timing of scattered polarized light. Following the results of polarization studies in type I nuclei and of dynamical studies of MBHBs with circumbinary discs, we assume a coplanar equatorial scattering ring, whose elements contribute differently to the total polarized flux, due to different scattering angles, levels of Doppler boost, and line-of-sight time delays. We find that in the presence of an MBHB, both the degree of polarization and the polarization position angle have periodic modulations. The polarization angle oscillates around the semiminor axis of the projected MBHB orbital ellipse, with a frequency equal either to the binary’s orbital frequency (for large scattering screen radii), or twice this value (for smaller scattering structures). These distinctive features can be used to probe the nature of periodic MBHB candidates and to compile catalogues of the most promising sub-pc MBHBs. The identification of such polarization features in gravitational-wave (GW) detected MBHBs would enormously increase the amount of physical information about the sources, allowing the measurement of the individual masses of the binary components, and the orientation of the line of nodes on the sky, even for monochromatic GW signals.}, author = {Dotti, Massimo and Bonetti, Matteo and D’Orazio, Daniel J and Haiman, Zoltán and Ho, Luis C}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {212--223}, publisher = {Oxford University Press}, title = {{Binary black hole signatures in polarized light curves}}, doi = {10.1093/mnras/stab2893}, volume = {509}, year = {2021}, }