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Articles 1 - 29 of 29
Full-Text Articles in Physics
Black Holes, Wormholes, And Extra Dimensions, Maria Babiuc-Hamilton
Black Holes, Wormholes, And Extra Dimensions, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
No abstract provided.
New Numerical Code For Black Hole Initial Data, Maria Babiuc-Hamilton
New Numerical Code For Black Hole Initial Data, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
There are no exact solutions of Einstein Equations that describes a bound system radiating gravitational waves. One needs to resort to numerical simulations, or analytical approximation methods. Current methods to constrained initial data exhibit junk radiation and ambiguities about constrained and free data. It was mathematically proved that given the correct initial data, Einstein equation will yield the expected solution.
Undergraduate Research In Gravitational Waves Astronomy At Marshall University, Maria Babiuc-Hamilton
Undergraduate Research In Gravitational Waves Astronomy At Marshall University, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
This is a presentation of undergraduate student research into gravitational waves at Marshall University.
Dawn Of Gravitational Wave Astronomy, Maria Babiuc-Hamilton
Dawn Of Gravitational Wave Astronomy, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
This presentation chronicles the discovery of gravity waves.
Learning To Teach And Teaching To Learn, Maria Babiuc-Hamilton
Learning To Teach And Teaching To Learn, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
New studies show that students do better in science classes that are taught interactively. We compare two different pedagogical approaches in teaching introductory physics: the lecture-based method, the active learning laboratories. We present the data on student performance on exams, homework, lab activities and tests, from 126 students taking the 200-level introductory physics courses at Marshall University, in Huntington, WV. We discuss the efficiency of each method in fostering the success of students in the introductory physics courses. We find that subtle differentiations can be implicitly detected in students’ exam grades, homework, participation, and choice of major.
The First Open-Source General Relativistic Force-Free Electrodynamics Code, Maria Babiuc-Hamilton, Zach Etienne, Mew-Bing Wan
The First Open-Source General Relativistic Force-Free Electrodynamics Code, Maria Babiuc-Hamilton, Zach Etienne, Mew-Bing Wan
Maria C. Babiuc-Hamilton
We are writing the first open-source, general relativistic force-free electrodynamics code: GiRaFFE. The goal is to numerically simulate neutron star and black hole magnetospheres. The GiRaFFE is alive! It has passed a number of 1D code validation tests, and 3D tests are underway. We plan to release the code and test suite initial data routines open-source to the community.
Towards A Standardized Characteristic Extraction Tool, Maria Babiuc-Hamilton
Towards A Standardized Characteristic Extraction Tool, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Knowing the precise details of the gravitational wave signature obtained from numerical simulations of binary black hole mergers is a key requirement for meaningful detection and scientific interpretation of the data. However, the waveforms are not easy to be accurately computed. The importance of this problem to the future of gravitational wave astronomy is well recognized. Cauchy-Characteristic Extraction (CCE) is the most precise and refined extraction method available. The CCE technique connects the strong-field Cauchy evolution of the spacetime near the merger to the characteristic evolution to future null infinity where the waveform is extracted in an unambiguous way. Recently, …
Simulating Magnetospheres With Numerical Relativity: The Giraffe Code, Maria Babiuc-Hamilton
Simulating Magnetospheres With Numerical Relativity: The Giraffe Code, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Numerical Relativity is successful in the simulation of black holes and gravitational waves. In recent years, teams have tackled the problem of the interaction of gravitational and electromagnetic waves. We developed a new code for the numerical simulation of neutron and black hole magnetospheres, using the FFE formalism. We tested the performance of the new code named GiRaFFE, in 1D and 3D test suits. We will study magnetospheres, focusing on jets by the Blandford -Znajek mechanism.
Cauchy-Characteristic Patching With Improved Accuracy, Maria Babiuc-Hamilton
Cauchy-Characteristic Patching With Improved Accuracy, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.
Towards A Fully Nonlinear Cauchy Characteristic Extraction, Maria Babiuc-Hamilton
Towards A Fully Nonlinear Cauchy Characteristic Extraction, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
The artificial finite outer boundary present in Cauchy codes introduce two sources of error: The outer boundary condition and waveform extraction at an inner worldtube. The problem of proper boundary condition for a radiating system can be solved only by extension to Ι+ (conformal compactification). Cauchy Characteristic Extraction (CCE) offers a means to avoid these errors.
Towards Improved Accuracy Of Gravitational Waves Extraction, Maria Babiuc-Hamilton
Towards Improved Accuracy Of Gravitational Waves Extraction, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Results in developing two new methods to improve the accuracy of waveform extraction using characteristic evolution. Numerical method: circular boundaries, with angular dissipation in the characteristic code. Geometric method: computation of Weyl tensor component Y4 at null infinity, in a conformally compactified treatment. Comparison and calibration in tests problems based upon linearized waves.
Gravitational & Electromagnetic Waves On The Null Cone, Maria Babiuc-Hamilton
Gravitational & Electromagnetic Waves On The Null Cone, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Bondi (1962) proved mathematically the existence of gravitational waves at null infinity. He found an exact solution of Einstein equations. Within this metric, he calculated the loss of mass due to the emission of gravitational waves. The mas of a system is constant if and only if there is no news. If there is news, the mass decreases as long as there are news.
Testing A Model For The Well-Posedness Of The Cauchy-Characteristic Problem In Bondi Coordinates, Maria Babiuc-Hamilton, Jeff Winicour
Testing A Model For The Well-Posedness Of The Cauchy-Characteristic Problem In Bondi Coordinates, Maria Babiuc-Hamilton, Jeff Winicour
Maria C. Babiuc-Hamilton
Gravity waves reveal colliding black holes, galaxies, the birth of a black hole in a supernova and the growth pains of our universe. Gravitational waves are unambiguous measured only at future null infinity.
Steps Towards A Nonlinear Cauchy-Characteristic Code Patching, Maria Babiuc-Hamilton
Steps Towards A Nonlinear Cauchy-Characteristic Code Patching, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.
Characteristics Of Gravitational And Electromagnetic Radiation, Maria Babiuc-Hamilton
Characteristics Of Gravitational And Electromagnetic Radiation, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Gravitational waves from the early universe are detectable, but detection is difficult. The strain is extremely small of magnitude 10-3 the width of a proton. There are detection and computational challenges.
An Analysis Of The Gravitational Waves Null Memory, Maria Babiuc-Hamilton
An Analysis Of The Gravitational Waves Null Memory, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Gravitational wave astronomy sees (hears) gravitational waves by observing the phenomena of gravitational and electromagnetic memory, and the formation of trapped surfaces and horizons.
Tools For Gravitational Wave Astronomy, Maria Babiuc-Hamilton
Tools For Gravitational Wave Astronomy, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Gravitational waves have been confirmed. Tools are available for their study, including the Einstein Toolkit, SimulationTools and the SXS Gravitational Waveform Database.
Gravity & Electromagnetism On The Null Cone, Maria Babiuc-Hamilton
Gravity & Electromagnetism On The Null Cone, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Gravitational and electromagnetic radiation travel along light rays, which are principal null directions in space-time. They are characteristic surfaces of Einstein and Maxwell equations. In characteristic coordinates, the field is described by ordinary differential equations.
A New Algorithm For The Numerical Computation Of Gravitational Waves, Maria Babiuc-Hamilton, Jeff Winicour
A New Algorithm For The Numerical Computation Of Gravitational Waves, Maria Babiuc-Hamilton, Jeff Winicour
Maria C. Babiuc-Hamilton
With gravitational waves, Gravitational Wave Astronomy can “see” colliding back holes and galaxies, the birth of a black hole in a supernova, the growth pains of our universe and the structure of spacetime.
A Hyperbolic Solver For Black Hole Initial Data In Numerical Relativity, Maria Babiuc-Hamilton, Jeff Winicour, I. Racz
A Hyperbolic Solver For Black Hole Initial Data In Numerical Relativity, Maria Babiuc-Hamilton, Jeff Winicour, I. Racz
Maria C. Babiuc-Hamilton
Initial data in numerical relativity. The constraints are formulated as elliptic equations, parabolic equations and strongly hyperbolic equations. This presentation is about a different approach to initial data for black holes, the strongly hyperbolic method.
Adding Light To The Gravitational Waves On The Null Cone, Maria Babiuc-Hamilton
Adding Light To The Gravitational Waves On The Null Cone, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Recent interesting astrophysical observations point towards a multi-messenger, multi-wavelength approach to understanding strong gravitational sources, like compact stars or black hole collisions, supernovae explosions, or even the big bang. Gravitational radiation is properly defined only at future null infinity, but usually is estimated at a finite radius, and then extrapolated. Our group developed a characteristic waveform extraction tool, implemented in an open source code, which computes the gravitational waves infinitely far from their source, in terms of compactified null cones, by numerically solving Einstein equation in Bondi space-time coordinates. The goal is extend the capabilities of the code, by solving …
Steps Towards The Well-Posedness Of The Characteristic Evolution For The Einstein Equations, Maria Babiuc-Hamilton
Steps Towards The Well-Posedness Of The Characteristic Evolution For The Einstein Equations, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
The correct modeling of gravitational radiation is a key requirement for a meaningful detection and interpretation of data. The Cauchy-characteristic technique connects the strong-field Cauchy evolution of the space-time near the black-hole merger to the characteristic evolution at future null infinity, where the waveform is properly defined. The PITT Null code, publicly available, is the most precise and refined computational method for the extraction of gravitational waves, but is not well-posed. The numerical relativity community recognizes that a well-posed problem is the only way to ensure that a code is stable and dependable. The well-posedness of the null-timelike problem for …
Gravitational And Electromagnetic Waves On The Null Cone, Maria Babiuc-Hamilton
Gravitational And Electromagnetic Waves On The Null Cone, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
Gravitational radiation is properly defined only at future null infinity, but mathematically it is estimated at a finite radius, and then extrapolated. Our group developed a characteristic waveform extraction tool, implemented in an open source code, which computes the gravitational waves infinitely far from their source, in terms of compactified null cones, by numerically solving Einstein equation. We add electromagnetic waves to the null cone, by deriving a formulation of the Einstein-Maxwell equations suitable to be numerically implemented into a characteristic code, that will evolve and calculate both the gravitational waves and their electromagnetic counterparts all the way to infinity.
Well-Posedness Of Characteristic Evolution In Bondi Coordinates, Maria Babiuc-Hamilton, Jeff Winicour
Well-Posedness Of Characteristic Evolution In Bondi Coordinates, Maria Babiuc-Hamilton, Jeff Winicour
Maria C. Babiuc-Hamilton
Gravitational waves carry information about their source, and their detection will uncover facets of our universe, otherwise invisible. Recently, we made publicly available a waveform computation tool, the PITT code, as part of the Einstein Toolkit open software for relativistic astrophysics. The code implements the “characteristic method,” which computes the gravitational waves infinitely far from their source in terms of compactified light cones. We proved that our code produces waveforms that satisfy the demands of next generation detectors. However, the main problem is that the well-posedness of the Einstein equations in characteristic formulation is not proven. Here we present our …
High Gravitational Waveform Accuracy At Null Infinity, Maria Babiuc-Hamilton
High Gravitational Waveform Accuracy At Null Infinity, Maria Babiuc-Hamilton
Maria C. Babiuc-Hamilton
The aim of Cauchy-characteristic extraction is to provide a standardized waveform extraction tool for the numerical relativity community. The new extraction tool contains major improvements and corrections to previous versions and displays convergence. The error introduced by CCE satisfies the time domain criteria required for advanced LIGO data analysis. The importance of accurate waveforms to the gravitational wave astronomy has created an urgency for tools like CCE. The source code has been released to the public and is available as part of the Einstein Toolkit. We welcome applications to a variety of generic Cauchy codes implementing Einstein Equations of General …
Using Radial Basis Functions To Interpolate Along Single-Null Characteristics, Maria Babiuc-Hamilton, Clyde E. Meador
Using Radial Basis Functions To Interpolate Along Single-Null Characteristics, Maria Babiuc-Hamilton, Clyde E. Meador
Maria C. Babiuc-Hamilton
The Cauchy-Characteristic Extraction (CCE) technique is the most precise method available for the computation of the gravitational waves obtained from numerical simulations of binary black hole mergers. This technique utilizes the characteristic evolution to extend the simulation to null infinity, where the waveform is computed in inertial coordinates. Although we recently made CCE publicly available to the numerical relativity community, there is still room for improvement, and the most important is enhancing the overall accuracy of the code, by upgrading the numerical methods used for interpolation and differentiation. One of the most promising ways is to use the Radial Basis …
Testing The Well-Posedness Of Characteristic Evolution Of Scalar Waves, Maria Babiuc-Hamilton, Heinz Otto Kreiss, Jeffrey Winicour
Testing The Well-Posedness Of Characteristic Evolution Of Scalar Waves, Maria Babiuc-Hamilton, Heinz Otto Kreiss, Jeffrey Winicour
Maria C. Babiuc-Hamilton
Recent results have revealed a critical way in which lower order terms affect the well-posedness of the characteristic initial value problem for the scalar wave equation. The proper choice of such terms can make the Cauchy problem for scalar waves well posed even on a background spacetime with closed lightlike curves. These results provide new guidance for developing stable characteristic evolution algorithms. In this regard, we present here the finite difference version of these recent results and implement them in a stable evolution code. We describe test results which validate the code and exhibit some of the interesting features due …
Strategies For The Characteristic Extraction Of Gravitational Waveforms, Maria C. Babiuc-Hamilton, N. T. Bishop, B´Ela Szila´Gyi, Jeffrey Winicour
Strategies For The Characteristic Extraction Of Gravitational Waveforms, Maria C. Babiuc-Hamilton, N. T. Bishop, B´Ela Szila´Gyi, Jeffrey Winicour
Maria C. Babiuc-Hamilton
We develop, test, and compare new numerical and geometrical methods for improving the accuracy of extracting waveforms using characteristic evolution. The new numerical method involves use of circular boundaries to the stereographic grid patches which cover the spherical cross sections of the outgoing null cones. We show how an angular version of numerical dissipation can be introduced into the characteristic code to damp the high frequency error arising form the irregular way the circular patch boundary cuts through the grid. The new geometric method involves use of the Weyl tensor component Ψ4 to extract the waveform as opposed to the …
Characteristic Extraction Tool For Gravitational Waveforms, Maria C. Babiuc-Hamilton, B´Ela Szila´Gyi, Jeffrey Winicour, Yosef Zlochower
Characteristic Extraction Tool For Gravitational Waveforms, Maria C. Babiuc-Hamilton, B´Ela Szila´Gyi, Jeffrey Winicour, Yosef Zlochower
Maria C. Babiuc-Hamilton
We develop and calibrate a characteristic waveform extraction tool whose major improvements and corrections of prior versions allow satisfaction of the accuracy standards required for advanced LIGO data analysis. The extraction tool uses a characteristic evolution code to propagate numerical data on an inner worldtube supplied by a 3+1 Cauchy evolution to obtain the gravitational waveform at null infinity. With the new extraction tool, high accuracy and convergence of the numerical error can be demonstrated for an inspiral and merger of mass M binary black holes even for an extraction worldtube radius as small as R=20M. The tool provides a …