A5047008257- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Geophysics and Sensor Technology
- Quantum Electrodynamics and Casimir Effect
- High-pressure geophysics and materials
- Noncommutative and Quantum Gravity Theories
- Solar and Space Plasma Dynamics
- Computational Physics and Python Applications
- Quantum Mechanics and Applications
- Advanced Thermodynamics and Statistical Mechanics
- Quantum, superfluid, helium dynamics
- Nonlinear Waves and Solitons
- Law and Political Science
- Relativity and Gravitational Theory
- Stellar, planetary, and galactic studies
- Spectroscopy and Quantum Chemical Studies
- Nuclear Physics and Applications
- Nonlinear Photonic Systems
- Mechanical and Optical Resonators
- Cold Atom Physics and Bose-Einstein Condensates
- Catalysis and Oxidation Reactions
Max Planck Institute for Gravitational Physics
2021-2025
University of Illinois Urbana-Champaign
2019-2025
University of Nottingham
2022
University of Tübingen
2022
Bulgarian Academy of Sciences
2022
Institute for Nuclear Research and Nuclear Energy
2022
Koç University
2022
Institute of Mathematics and Informatics
2022
Sofia University "St. Kliment Ohridski"
2022
Montana State University
2017-2021
One century after its formulation, Einstein's general relativity (GR) has made remarkable predictions and turned out to be compatible with all experimental tests. Most of these tests probe the theory in weak-field regime, there are theoretical reasons believe that GR should modified when gravitational fields strong spacetime curvature is large. The best astrophysical laboratories strong-field gravity black holes neutron stars, whether isolated or binary systems. We review motivations...
We identify a class of scalar-tensor theories with coupling between the scalar and Gauss-Bonnet invariant that exhibit spontaneous scalarization for both black holes compact stars. In particular, these formally admit all stationary solutions general relativity, but are not dynamically preferred if certain conditions satisfied. Remarkably, their mass lies within one many narrow bands. find evidence can occur in neutron stars as well.
We infer the mass distribution of neutron stars in binary systems using a flexible Gaussian mixture model and use Bayesian selection to explore evidence for multimodality sharp cut-off distribution. find overwhelming bimodal distribution, agreement with previous literature, report first time positive at maximum star mass. measure be 2.0 M⊙ < mmax 2.2 (68 per cent), 2.6 (90 is robust against choice removing most extreme (highest mass) from data set. If this interpreted as stable allowed by...
It was recently shown that a scalar field suitably coupled to the Gauss-Bonnet invariant $\mathcal{G}$ can undergo spin-induced linear tachyonic instability near Kerr black hole. This appears only once dimensionless spin $j$ is sufficiently large, is, $j \gtrsim 0.5$. A hallmark of spontaneous scalarization. Focusing, for illustrative purposes, on class theories do exhibit this instability, we show stationary, rotating hole solutions indeed have hair threshold exceeded, while holes lie below...
Scalar-tensor theories of gravity where a new scalar degree freedom couples to the Gauss-Bonnet invariant can exhibit phenomenon spontaneous black hole scalarization. These admit both classic solutions predicted by general relativity as well novel hairy solutions. The stability holes is strongly dependent on precise form scalar-gravity coupling. A radial investigation revealed that all scalarized are unstable when coupling between field and quadratic in scalar, whereas stable exist for...
Gravitational-wave astronomy offers not only new vistas into the realm of astrophysics, but it also opens an avenue for probing, first time, general relativity in its strong-field, nonlinear, and dynamical regime, where theory's predictions manifest themselves their full glory. We present a study whether gravitational-wave events detected so far by LIGO-Virgo scientific collaborations can be used to probe higher-curvature corrections relativity. In particular, we focus on two examples:...
Gravitational wave observations of compact binaries allow us to test general relativity (and modifications thereof) in the strong and highly-dynamical field regime gravity. Here we confront two extensions relativity, dynamical Chern-Simons Einstein-dilaton-Gauss-Bonnet theories, against gravitational sources from GWTC-1 GWTC-2 catalogs by LIGO-Virgo Collaboration. By stacking posterior individual events, strengthen constraint on square root coupling parameter gravity $\sqrt{\alpha_{\rm \tiny...
Recent observations of compact astrophysical objects have opened the possibility to probe nature gravity in its strong-field regime. Such could reveal deviations from general relativity or standard model. Spontaneous scalarization, which is controlled by scalar-field couplings gravity, leads a behavior that resembles phase transition: scalar induces measurable effects regime while remaining undetectable weak-field gravitational experiments. This review presents spontaneous scalarization...
Detecting gravitational waves from coalescing compact binaries allows us to explore the dynamical, nonlinear regime of general relativity and constrain modifications it. Some gravitational-wave events observed by LIGO-Virgo Collaboration have sufficiently high signal-to-noise ratio in merger, allowing probe relaxation remnant black hole its final, stationary state---the so-called black-hole ringdown, which is characterized a set quasinormal modes. Can we use ringdown deviations relativity,...
Some models (such as the Skyrme model, a low-energy effective field theory for quantum chromodynamics) suggest that high-density matter prevailing in neutron star (NS) interiors may be significantly anisotropic. Anisotropy is known to affect bulk properties of nonrotating NSs general relativity (GR). In this paper we study effects anisotropy on slowly rotating stars GR. We also consider one most popular extensions Einstein's theory, namely scalar–tensor theories allowing spontaneous...
It has recently been shown that nontrivial couplings between a scalar and the Gauss-Bonnet invariant can give rise to black hole spontaneous scalarization. Theories exhibit this phenomenon are among leading candidates for testing gravity with upcoming observations. All models considered so far have focused on specific forms coupling, neglecting self-interactions. In work, we take first steps towards placing more robust theoretical footing by considering leading-order self-interactions as...
The combination of gravitational-wave and x-ray observations neutron stars provides new information on the mass distribution in these as well confirmation Einstein's theory gravity.
Scalar fields coupled to the Gauss-Bonnet invariant can undergo a tachyonic instability, leading spontaneous scalarization of black holes. Studies this effect have so far been restricted single hole spacetimes. We present first results on dynamical in head-on collisions and quasicircular inspirals binaries with numerical relativity simulations. show that either form scalarized remnant or dynamically descalarize by shedding off its initial scalar hair. The observational implications these...
The detection of gravitational waves from compact binary mergers by the LIGO/Virgo Collaboration has, for first time, allowed us to test relativistic gravity in its strong, dynamical, and nonlinear regime, thus opening a new arena confront general relativity (and modifications thereof) against observations. We consider theory which modifies introducing scalar field coupled parity-violating curvature term known as dynamical Chern-Simons gravity. In this theory, spinning black holes are...
Particular couplings between a scalar field and the Gauss-Bonnet invariant lead to spontaneous scalarization of black holes. Here we continue our work on simulating this phenomenon in context binary hole systems. We consider negative coupling for which black-hole spin plays major role process. find two main phenomena: (i) dynamical descalarization, initially scalarized holes form an unscalarized remnant, (ii) scalarization, whereby late merger can cause hair grow. An important consequence...
The plunge-merger stage of the binary-black hole coalescence, when bodies' velocities reach a large fraction speed light and gravitational-wave luminosity peaks, provides unique opportunity to probe gravity in dynamical nonlinear regime. How much do predictions general relativity differ from ones other theories for this binary evolution? To address question, we develop parametrized waveform model, within effective-one-body formalism, that allows deviations plunge-merger-ringdown stage. As...
A bstract We present the conservative effective two-body Hamiltonian at third order in post-Newtonian expansion with gravitoelectric quadrupolar dynamical tidal-interactions. Our derivation of Lagrangian is based on diagrammatic field theory approach and it involves Feynman integrals up to three loops, which are evaluated within dimensional regularization scheme. The elimination divergent terms occurring requires addition counterterms ensure finite observables, thereby introducing a...
The response of black holes to small perturbations is known be partially described by a superposition quasinormal modes. Despite their importance enable strong-field tests gravity, little nothing about what overtones and quasinormal-mode amplitudes are like for in extensions general relativity. We take first step this direction study arguably the simplest model that allows first-principle calculations made: nonrotating hole an effective-field-theory extension relativity with...
We study black hole solutions at first order in the Hartle-Thorne slow-rotation approximation Horndeski gravity theories. derive equations of motion including also cases where scalar depends linearly on time. In formalism, all first-order rotational corrections are described by a single frame-dragging function. show that function is exactly same as general relativity for known shift symmetric theories, with exception theories linear coupling to Gauss-Bonnet invariant. Our results extend...
We present a general formulation to analyze the structure of slowly rotating relativistic stars in broad class scalar-tensor theories with disformal coupling matter. Our approach includes generalized kinetic terms, generic scalar field potentials and contains conformal as particular limits. In order investigate how affects stars, we propose minimal model massless theory detail spontaneous scalarization neutron stars. show that for negative values parameter between matter, can be suppressed,...
Horndeski's theory of gravity is the most general scalar-tensor with a single scalar whose equations motion contain at second-order derivatives. A subsector known as ``Fab Four'' allows for dynamical self-tuning quantum vacuum energy, and therefore it has received particular attention in cosmology possible alternative to $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Here we study compact stars Fab Four gravity, which includes special cases relativity (``George''),...
One of the central goals newborn field gravitational wave astronomy is to test gravity in highly nonlinear, strong regime characterizing spacetime black holes. In particular, "black hole spectroscopy" (the observation and identification quasinormal mode frequencies signal) expected become one main tools for probing structure dynamics Kerr this paper we take a significant step towards that goal by constructing "post-Kerr" formalism. The formalism incorporates parametrized but general...
Much of our physical intuition about black hole quasinormal modes in general relativity comes from the eikonal/geometric optics approximation. According to well-established eikonal model, fundamental mode represents wave packets orbiting vicinity hole's geodesic photon ring, slowly peeling off towards event horizon and infinity. Besides its strength as a ``visualisation'' tool, approximation also provides simple quantitative method for calculating frequency, close agreement with rigorous...
Spontaneous scalarization is a mechanism that allows scalar field to go undetected in weak gravity environments and yet develop nontrivial configuration strongly gravitating systems. At the perturbative level it manifests as tachyonic instability around spacetimes solve Einstein's equations. The endpoint of this can significantly modify compact object's structure produce observational signatures field's presence. Does such exists for vector fields? Here we revisit model constitutes most...
In a recent series of papers we have shown how the eikonal/geometrical optics approximation can be used to calculate analytically fundamental quasinormal mode frequencies associated with coupled systems wave equations, which arise, for instance, in study perturbations black holes gravity theories beyond General Relativity. As continuation this series, here focus on modes nonrotating scalar Gauss-Bonnet assuming small-coupling expansion. We show that axial are purely tensorial and described...