Welcome to Ruxandra Bondarescu's Page!



Welcome to my page. I am a postdoctoral fellow in the Physics Department at the University of Zurich. My scientific interests are in astrophysics, general relativity, cosmology, gravitational wave physics and geophysics; recently I have also done some work at the interface between general relativity and geophysics.

This is a copy of my CV . I am currently applying for professor positions world-wide.

In addition to being published in various journals, all my scientific work is freely available on the arXiv (note this is the arXiv link to my short author publication list; it excludes the LIGO collaboration papers). I also have a profile on google scholar and one on research gate .

If you have questions related to my work please feel free to email me at ruxandraATphysik.uzh.ch. You can also read about some of the things I do on my personal blog .
I have worked on the following topics:

1. The applicability of atomic clocks in testing general relativity, alternative theories of gravity, and geophysics.
We investiaged the extend to which a space-craft carrying an atomic clock in an elliptic orbit around the Earth is sensitive to higher order relativistic effects and alternative theories of gravity . At ground level, portable atomic clocks, can add detail to satellite maps and help us in understanding the interior structure of the Earth. Our discussion of the potential applicability of atomic clocks to locally measure the geoid, i.e., equipotential surface (surface of constant tick rate) that extends the mean sea level to continents, received significant media attention: e.g., here is the MIT Technology Review of my paper.

2. Precursor flares for short gamma ray bursts.
We investigate the resonant excitation of neutron star modes by tides and find that the driving of the L=2, m=2 crust-core interface mode can lead to shattering of the NS crust seconds before the merger of a NS-NS or NS-BH binary. This mechanism can explain precursor flares that happen before short GRBs. Such flares that have already been observed by Swift-BAT, Fermi and Suzaku. For more see the right pitch to shatter a neutron star or the original paper & Dave's summary with more pictures and links to other press releases. Our paper is also mentioned in the GRB section of wikepedia .

3. Nonlinear effects in the r-mode instability of neutron stars.
My PhD thesis in collaboration with Profs. Saul Teukolsky and Ira Wasserman was on r-modes. Rmodes are oscillations that occur in rotating fluids. In rapidly rotating neutron stars these modes can be unstable. The instability is driven by the gravitational radiation reaction. The most relvant mode for gravitational radiation emisson is the Rossby wave with L=m=2. This mode is unstable when gravitational driving dominates viscous dissipation. Once the amplitude L=m=2 r-mode passes its parameteric instability threshold amplitude, it excites other near-resonant modes in the system and nonlinear effects become important converting rotational energy to mode energy and gravitational radiation and thus slowing the star down. Stars that spin fast enough to have active r-modes are either old recycled neutron stars that are spun up by a binary companion (see my paper on R-modes in LMXBs here ) or very young pulsars ( newborn neutron stars paper ). My most recent work on this subject was published in the Astrophysical Journal. I also summarize it in the following post: How fast can neutron stars spin?" .

4. Luke-warm Dark Matter.
Ultralight dark matter particles could Bose-condense into halos and could be luke-warm while remaining consistent with existent data from WMAP, Planck, and Big Bang Nucleosynthesis. For more see blog post and/or the techical article we wrote .

5. Beams and mirror shapes for future ground-based gravitational wave interferometers.
Thermal noise will be the dominant form of noise in the most sensitive frequency band of Advanced LIGO detectors. We look for alternative mirror and beam shapes that minimize the thermal noise while keeping the diffraction loss constant, and find that thermal noise can be reduced by up to 60% relative to the currently used Gaussian beams. Our work was published in this Phys. Rev. D article.

6. Simulations of boson stars and soliton stars in 3D.
Boson stars (complex scalar field configurations; potential particle candidates include WIMPs) and soliton stars (real scalar field configurations; the most prominent scalar particles candidates are axions) are alternative to black holes. Light axions could have been created by non-thermal processes in the early universe leaving them slow moving and compatible with preferred cold-dark matter models. Stars composed of scalar particles (compact scalar objects) would be an exotic source of gravitational waves. Their detection would confirm the presence of scalar field dark matter. We studied propreties of these stars using a 3D code based on the Cactus Computational Toolkit (www.cactuscode.org), their stability under spherical and non-spherical perturbations and the quasi-normal mode structure of the gravitational waves they could produce. The results were published in CQG ( see boson stars paper ) and Phys. Rev. D ( see soliton stars paper ).


Refereed Publications

12. A. Scharer, R. Angelil R. Bondarescu , and P. Jetzer, "Testing Scalar-Tensor Theories and
Parametrized Post-Newtonian Parameters in Earth Orbit", Phys. Rev. D90 123005 (2014). [arXiv:1410:7914]

11. R. Angelil, P. Saha, R. Bondarescu , P. Jetzer, A. Scharer, A. Lundgren,
"Spacecraft Clocks and Relativity: Prospects for Future Satellite Missions", Phys. Rev. D89 , 064067 (2014). [arXiv:1402.6698]

10. R. Bondarescu, and I. Wasserman, "Nonlinear Development of the R-mode Instability and the Maximum Rotation Rate of Neutron Stars", Astrophys. Journal 778 , 9 (2013). [arXiv:1305.2335].

9. R. Bondarescu, M. Bondarescu, G. Hetenyi, L. Boschi, P. Jetzer,
and J. Balakrishna, "Geophysical Applicability of Atomic Clocks: Direct Continental Geoid Mapping",
Geophysical Journal International 191, pages 78-92, 2012. Journal Article
http://arxiv.org/abs/1209.2889. Description in the News.

8. D. Tsang, J. S. Read, T. Hinderer, A. L. Piro, and R. Bondarescu ,
"Resonant Shattering of Neutron Star Crusts", arXiv:1110.0467, Phys. Rev. Lett. 108 , 011102 (2012).

7. A. P. Lundgren, M. Bondarescu, R. Bondarescu and J. Balakrishna,
"Luke-warm dark matter: Bose condensation at finite temperatures. ", arXiv:1001.0051 ApJL 715 , L35 (2010).

6. R. Bondarescu, S. Teukolsky, and I. Wasserman,
"Spinning Down Newborn Neutron Stars: Nonlinear Development of the R-mode Instability",
arXiv:0809.3448 Phys. Rev. D 79, 104003 (2009).

5. A. P. Lundgren, R. Bondarescu , D. Tsang, M. Bondarescu,
"Finite Mirror Effects in Advanced Interferometric Gravitational Wave Detectors",
arxiv:0710.3808, Phys. Rev. D 77, 042003 (2008).

4. J. Balakrishna, R. Bondarescu , G. Daues, M. Bondarescu, "Numerical Simulations of Oscillating Soliton Stars: Excited States in Spherical Symmetry and Ground State Evolutions in 3D", arxiv:0710.4131, Phys. Rev. D 77, 024028 (2008).

3. R. Bondarescu, S. Teukolsky, and I. Wasserman,
"Spin Evolution of Accreting Neutron Stars: Nonlinear Development of the R-mode Instability",
arXiv:0704.0799, Phys. Rev. D 76, 064019 (2007).

2. J. Balakrishna, R. Bondarescu, G. Daues, F. Guzman, and E. Seidel,
"Evolution of 3D Boson Stars with Waveform Extraction",
Class. Quantum Grav. 23 (2006) 2631-2652, gr-qc/0602078.

1. R. Bondarescu, G. Allen, G. Daues, I. Kelley, M. Russell, E. Seidel, J. Shalf, M. Tobias,
"The Astrophysics Simulation Collaboratory Portal: a Framework for Effective Distributed Research",
Future Generation Computing Systems 21 (2005) 259-270, Special Issue on Advanced Grid Technologies.
PDF version of the paper   Abstract through Science Direct

Ph.D. Thesis Ruxandra Bondarescu, Cornell University, August 2008. Articles about me
Interviu printre stele, Ziarul Timpul, Aprilie, 2011

Work in the Spotlight
1. The Geophysical Applicability of Atomic Clocks: Direct Continental Geoid Mapping work was widely featured in the news. Read MIT Technology review here , and the Welt der Phyisk review. There were many others.

2. The resonant shattering of neutron stars work was spotlighted by Physical Review Letters as extraordinary research! Read it here! Some other news stories about this work can be found in arstechnica and New Scientist.

Counter that shows the number of unique hits starting from Jan 31, 2013.