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Prof. Myoung-Hwan Kim receives 2018 Outstanding Young Researcher Award from AKPA

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Prof. Myoung-Hwan Kim received the 2018 Outstanding Young Researcher Award from the Association of Korean Physicists in America (AKPA) for his contribution to modern material research including low-dimensional, topological, and correlated systems with terahertz and infrared lasers. Prof. Kim has more than 10 years of experience in far/mid/near infrared Hall measurements for various types of materials including topological insulators, graphene mono- and multilayers, itinerant ferromagnets, superconductors, semiconductors, and insulators. The infrared Hall angle measurement is one of the most powerful way to disclose Fermi surface information, which are comparable with the results acquired from angular-resolved photoemission spectroscopy (ARPES) and de Haas-van Alphen oscillations. In addition, Prof. Kim has recently developed a new tool to measure polarimetric spectrum at underexplored mid/far infrared. Using this tool, Prof. Kim will observe a frequency evolution of quasi-particle scattering in a time-reversal symmetry broken system. This research will benefit the understanding of more complex spin-orbit coupled system. The award ceremony took place at the Korean Physical Society-AKPA Symposium at the Los Angeles Convention Center during the American Physical Society March meeting. Prof. Kim gave an award presentation on his research.
(For more details visit akpa.org)

Alondra Escobar receives award for best presentation at Gulf Coast Undergraduate Research Symposium

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Alondra Escobar, student in the Biophysics Research Laboratory, received an award from the Chemical and Biomolecular Engineering Department for Best Presentation in Materials Science at the Gulf Coast Undergraduate Research Symposium at Rice University on November 4, 2017. Alondra and her mentors, Drs. Natalia and Juan Guevara, have designed and developed a nanoscale optical microscopy system to study live human blood cells in buffered saline. Their invention makes it possible to obtain high resolution images of the complete surface of a single cell thereby creating an accurate record of cell size, volume, and topography. Alondra's aim is to create an atlas of human blood cells that can be used to identify anomalies that correlate to infectious diseases, genetic disorders, and malignancies. Congratulations!
(For more details, read the full article.)

Nareg Ohannesian and Anton Gribovskiy receive first prizes at UTRGV Graduate Research Symposium

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Physics graduate students Nareg Ohannesian and Anton Gribovskiy won the first and second prizes, respectively, at the UTRGV Graduate Research Symposium held on Feb 27 and 28, 2018 on both campuses. Nareg received the first prize ($1000) for his poster entitled "Development of PEEK-Magnetite Composites for Biomedical Applications". His research project has been supervised by Dr. Karen Martirosyan and reported experimental and theoretical studies for the feasibility of modifying physical and magnetic properties of Polyetheretherketone (PEEK) polymer by incorporating magnetite nanoparticles in its matrix. Anton received the second prize ($500) for his poster entitled "Analysis of Optical Properties of Integrated Silicon Microring Resonators Using GHz Modulation Techniques". His research project has been supervised by Dr. Malik Rakhmanov and reported on the design, fabrication, and characterization of microring resonators at UTRGV. Congratulations!
(For more details, read the full article.)

Prof. HyeongJun Kim receives UT System Rising STARs award.

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Prof. HyeongJun Kim received the prestigious UT System Rising STARs award. The award will go towards establishing research on single-molecule biophysics of genome organization at UTRGV. Dr. Kim will join our department from Harvard Medical School in spring 2018. Dr. Kim has been trained as a single-molecule biophysicist. Traditionally, biologists observed multiple (tens or even thousands of) molecules simultaneously and obtained "averaged" (ensemble) information. However, the advent of single-molecule biophysics techniques enabled scientists to observe "individual" biological molecules such as DNA or proteins one-by-one, getting very detailed information that cannot be obtained by traditional methods. Dr. Kim's research as a graduate student at the University of Illinois at Urbana-Champaign (UIUC) and postdoctoral fellow at Harvard Medical School focused on both single-molecule technology development and its application to answering biological questions. At UTRGV, Dr. Kim plans to carry out research on underlying working mechanisms of various DNA-associated proteins by utilizing his single-molecule biophysics expertise.

Prof. Mohanty was invited to deliver lectures on gravitational wave data analysis at the Chinese Academy of Sciences.

Dr. Mohanty was invited to deliver lectures on gravitational wave data analysis at the Chinese Academy of Sciences, Beijing, from Dec 2 to Dec 10, 2017. In the week-long series of lectures and labs, students learnt the fundamentals of statistical data analysis tools used in gravitational wave astronomy. In addition to the lecture series, Dr. Mohanty gave invited talks at the Kavli Institute for Astronomy and Astrophysics at Peking University, the Yau Mathematical Sciences Center at Tsinghua University, Wuhan University and the Center for Gravitational Experiments at the Huazhong University of Science and Technology. The image shows Dr. Mohanty (5th from the left) with participants of the lecture series at the Chinese Academy of Sciences (click on image for larger view).

LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars

For the first time, scientists have directly detected gravitational waves - ripples in space and time - in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light. Several astronomers, UTRGV-CGWA among them, participated in the discovery. See CGWA press release, Mario Diaz statement, UTRGV press release.

2017 Nobel Prize in Physics Awarded for the Detection of Gravitational Waves

The Nobel Prize in Physics 2017 was awarded to Rainer Weiss, a professor at the Massachusetts Institute of Technology, and Kip Thorne and Barry Barish, both of the California Institute of Technology. Profs. R Weiss and K. Thorne are the founders of the LIGO project. See CGWA press release.

Gravitational waves from a binary black hole merger observed by LIGO and Virgo

First Nanophotonic Device Built by Physics Department UTRGV

In March 2017, the Department of Physics operated its first silicon nano-photonic integrated circuit. The device consists of a large number of waveguides and micro-ring resonators which route and manipulate light. Silicon nano-photonic devices are intended to replace traditional micro-electronic circuits, such as processors that can be found in every computer. Successful operation of the device is recorded in the video showing one of the resonators turning on by light. The device was fabricated by PhD student Anton Gribovskiy who is conducting researchin silicon micro-ring resonators under supervision of Dr. Rakhmanov. "The process of fabrication was full of trials and errors and it took a lot of time to go from nothing to a working device." - said Anton who is currently enrolled in the UTRGV-UT Arlington Cooperative PhD Program and is a member of Optics and Nanophotonics Group at UTRGV. (For more details, read the full article.)

Prof. Benacquista has been selected as an NSF Program Director in the Division of Astronomy.

The National Science Foundation has selected Professor Matthew Benacquista of the Department of Physics and Astronomy to serve as a program director in the Division of Astronomy. His initial appointment is for one year, renewable for up to three years. The NSF will benefit from Dr. Benacquista's technical expertise to enhance the management, operation, and evaluation of the programs with the Astronomy Division. Dr. Benacquista's duties at the NSF will include long-range planning and budget development for astronomy, and advising the community of current and future funding opportunities. He will also be responsible for coordinating and collaborating with other programs in the NSF as well as other Federal agencies and organizations. He will begin working at the new NSF headquarters in Alexandria, Va on October 2, 2017. He will be supported in this appointment through a $180,000 grant to UTRGV from the NSF. UTRGV will benefit from Dr. Benacquista's knowledge and experiences that he will gain working in the program on policy-level matters and issues involving Astronomy at the Federal level.

Prof. Mohanty was invited to lecture at the "3rd International Winter School on Big Data", Feb 13-17, 2017, Bari, Italy.

The school was organized by University of Bari "Aldo Moro", Italy, and Rovira i Virgili University, Spain (see conference announcement). The topic of Prof. Mohanty's lectures was "Swarm Intelligence Methods and Optimization Problems in Big Data Analytics". Further details are available from the school's website http://grammars.grlmc.com/BigDat2017

Physics Professor Invents a Breakthrough Cobalt-based MRI Contrast Agent and Imaging System to Improve Cancer Cure

Dr. Karen Martirosyan, Professor of Physics has been awarded a patent titled "Cobalt-based MRI contrast agent and imaging system". The patent, US 9345790 B2, is associated with cancer research and development of novel, non-toxic cobalt-based contrast and imaging agents for use in enhanced medical imaging modalities and processes, as well as the manufacture of markers containing such contrast agents and uses in a variety of therapeutic applications and devices. This work is in collaboration with the UT MD Anderson Cancer Center (Prof. Steven Frank). The patented imaging agent comprising a complex of a cobalt ions and one or more of a ligand selected from the group consisting of halides, amino acids, amino acid derivatives, N-acyl-amino acids, chelating agents, polymers, or their combinations.
This patent is an important milestone towards further commercialization of the MRI implantable markers in clinical use since it further elaborates ways of effective cure of cancer by using Magnetic Resonance Imaging (MRI) in the planning, treatment, and post-implant evaluation for disease in various organs including the prostate, head and neck, breast, lung, brain, GI malignancies and sarcomas. The positive-signal 'MRI Marker' markers have already received FDA 510(k) clearance that can utilize real-time MRI-guided procedures, including prostate brachytherapy. The permanently implantable MRI marker technology allows improvement of positive MRI seed localization after brachytherapy offered to more than 200,000 men diagnosed with prostate cancer in the U.S. each year. Full details of the patent can be seen here: https://www.google.com/patents/US9345790

Eric Vallarino, MS in Physics UTB/TSC 2009, has been awarded a Yale Educator Award

The Yale Educator Recognition Program recognizes outstanding educators from around the world who have supported and inspired their students (see: https://admissions.yale.edu/educator-award). Matriculating students are invited to nominate high school educators, and a committee composed of Yale admissions officers reviews the nominations individually and designates recipients. Of this year's 326 nominees, who represent 33 states and 24 countries, 55 teachers and 28 counselors were selected to receive the award.

Physics professors receive UT System Valley STAR award

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Professors Hamidreza Ramezani and Myoung-Hwan Kim, Assistant Professors in the department of Physics, have each received the prestigious Valley STAR award from the University of Texas System in Spring 2016. The award to Myoung-Hwan has been granted for his proposal on Mid/Far infrared spectroscopy and microscopy system. The award to Hamidreza has been granted for his proposal on Exploring non-Hermitian Physics. In August of 2004, The University of Texas System Board of Regents approved an allocation of funds to be awarded to System institutions to help attract and retain the best qualified faculty. The STAR (Science and Technology Acquisition and Retention) program provides funding to help purchase state-of-the-art research equipment and make necessary laboratory renovations to encourage faculty members to perform their research at a UT institution. (See: https://www.utsystem.edu/offices/academic-affairs/stars-program). Dr. Ramezani has come to the UTRGV from the University of California, Berkeley, in January 2016. Dr. Kim joined at the same time from the Columbia University.

Student Kareem Wahid receives excellence award

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Mr. Kareem Wahid, Physics Major graduating this Spring, was awarded the inaugural UTRGV Honors College Excellence Award for the Best Honors Thesis. This is a single award given every year.

Dr. Malik Rakhmanov recognized for his mentorship of new faculty

Dr. Malik Rakhmanov (right), Associate Professor of Physics, received the 2016 New Faculty Support Program Mentor Award at a ceremony held May 5 in the Ballroom at the Edinburg Campus. Pictured left to right with Rakhmanov are Dr. Myoung-Hwan Kim, his mentee who nominated him for the award, and Dr. Parwinder Grewal, Dean of the College of Sciences.

Student Kareem Wahid receives prize

Kareem Wahid receives prize

Mr. Kareem Wahid, Physics Major at UTRGV, has received an award from the American Physical Society (APS) at its March 2016 meeting at Baltimore. Kareem receives this prize for being among the top undergraduate presenters at the APS Meeting. Kareem's research project has been advised by Dr. Yuanbing Mao, Associate Professor in the Department of Chemistry at UTRGV. The project, titled "Doped lanthanum hafnates as scintillating materials for high energy photon detection" is a collaboration between the Department of Physics and the Department of Chemistry, and also includes post-doctoral fellow, Madhab Pokhrel. Congratulations!

Andrea Silva was selected as the Outstanding International Female Student

International Women's Day was celebrated on the UTRGV Brownsville campus Thursday. Andrea Silva was selected as the Outstanding International Female Student. Dr. Karina Stiles-Cox, Chair of the Women's Faculty Network, presented her with the award. UTRGV. Andrea is a Physics Major. She is planning to graduate with a Bachelor's degree in Spring 2016. Andrea has been actively involved in undergraduate research under the supervision of Dr. Volker Quetschke. She has presented her research at many national and international conferences. She plans to pursue graduate study in Physics at UTRGV.

UTRGV Society of Physics Students named "Outstanding Chapter"

RIO GRANDE VALLEY, TEXAS - MARCH 7, 2016 - Demonstrating the wonders of physics and inspiring the next generation of physicists has earned the UTRGV Society of Physics Students (SPS) honors as an Outstanding Chapter for 2015 by the SPS National Council.

This is the first time the student group has earned "Outstanding" honors among schools in Zone 13. It is the top accolade from the National Council for community efforts and student outreach. Last year, the UTRGV SPS Chapter won the Distinguished Chapter award.

UTRGV Physics students get awards at APS meeting

Ms. Srbuhi Yolchinian and Mr. Glenn Grissom, both M.S. Physics students at UTRGV were among winners in American Physical Society's (APS) poster presentation competition at the Texas Section of APS (TSAPS) meeting in Fall 2015, held at the Baylor University in Waco, TX. The award carries a cash prize. Ms. Yolchinian's presentation was titled "Shape-dependent nanoenergetic gas generators based on bismuth trioxide nanoparticles". Ms. Yolchinian's research project has been supervised by Dr. Karen Martirosyan, Professor in the Physics department and Associate Dean of Research in the College of Sciences. Mr. Glenn Grissom's research, titled "Dye-Sensitized Photovoltaic Cells with Enhanced Exciton-Hole Separation and Barrier", has been supervised by Dr. Ahmed Touhami, Associate Professor in the Physics department.

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Research

Gravitational waves, as Einstein predicted

UTRGV Center for Gravitational Waves "The Amazing Discovery"

(Feb. 2016) For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein's 1915 general theory of relativity, and opens an unprecedented new window onto the cosmos.

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Publications

Faculty and students are engaged in fundamental research in relativistic astrophysics, gravitational wave astronomy, biophysics, nanoscience, and optics.

UT Rio Grande Valley Department of Physics Publications 2011-Present

Recent Research Highlights

Photons are bosons, namely, indistinguishable particles. This means that in principle we cannot independently select two similar photons traveling in opposite directions and trap one of them. In a letter accepted for publication in Phys. Rev. Lett. (H. Ramezani, P. K. Jha, Y. Wang, and X. Zhang, Nonreciprocal localization of photons, accepted to Phys. Rev. Lett.) H. Ramezani et al. have shown that indeed one can break this limitation and trap photons traveling in one direction in spatiotemporally modulated photonic lattices. Photons with exactly the same properties coming from the opposite direction can freely pass through the photonic lattice. Ramezani's proposal opens new avenues to design new devices like isolators, circulators, sensors, limiters, and even lasers.

LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars. For the first time, scientists have directly detected gravitational waves - ripples in space and time - in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light. The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector; and some 60 ground- and space- based telescopes. Among these 60, the TOROS (Transient Optical Robotic Observatory of the South), an international collaboration with more than 50 scientists, and lead by CGWA faculty and students, operated two telescopes: one in Co. Tololo, Chile and the other one in Bosque Alegre, Argentina. Top image: pseudo-color image of a small subsection of the FoV of the T80S telescopem, centered on the transient near galaxy NGC4993. Bottom: 3 times zoom in with the galaxy subtracted. See CGWA press release.

The LIGO Scientific Collaboration and the Virgo collaboration report the first joint detection of gravitational waves with both the LIGO and Virgo detectors. This is the fourth announced detection of a binary black hole system and the first significant gravitational-wave signal recorded by the Virgo detector, and highlights the scientific potential of a three-detector network of gravitational-wave detectors. The three-detector observation was made on August 14, 2017 at 10:30:43 UTC. The two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, and funded by the National Science Foundation (NSF), and the Virgo detector, located near Pisa, Italy, detected a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes. Image: Skymap showing the localization area of the event over the constellations in the sky (top) and the time series and frequency maps (bottom). A paper about the event, known as GW170814, has been accepted for publication in the journal Physical Review Letters. See CGWA press release.

"Pulsar timing array based search for supermassive black hole binaries in the Square Kilometer Array era", Yan Wang and Soumya D. Mohanty, Phys. Rev. Lett. 118, 151104 (2017). This article was chosen for the cover and as feature article of Physical Review Letters.
There is now strong observational evidence that most massive galaxies, including our own, host black holes - with masses ranging from million to billion solar masses - at their cores. The merger of galaxies containing such black holes should have lead to the formation of binary systems containing supermassive black holes. Gravitational waves emitted by such binaries, which are potentially detectable with the technique of Pulsar timing, would be the clearest signature of their existence. In this paper, we show that the detection of gravitational waves from Supermassive Black Holes Binaries is practically guaranteed when the Square Kilometer Array (SKA) - a next generation radio telescope - starts operation. This will happen through the discovery by SKA of thousands of milli-second pulsars - the most stable clocks in nature - which will boost the sensitivity of the pulsar timing technique by orders of magnitude. Our predictions are derived from a realistic simulation of a SKA-era array of timed pulsars (a "Pulsar Timing Array") and a rigorous, quantitative analysis of the corresponding data. This analysis also allows us to predict the accuracy with which a given binary can be localized on the sky. This enables future studies of joint observational strategies for supermassive black hole binaries using SKA at radio frequencies and the upcoming Large Synoptic Survey Telescope (LSST) in the optical.

Dr. Ahmed Touhami and collaborators have recently published a paper in Nature Biofilms. First author Kristin Kovach is a graduate student at UT Austin, co-advised by Dr. Touhami. The published research shows that over time bacteria can evolve the ability to strengthen their biofilms, making it harder for the host's immune cells to break them up and consume the bacteria. The Pseudomonas aeruginosa bacteria do this trick by secreting more and more of a carbohydrate that links up with proteins to form a tough, super glue-like network between bacteria. In cystic fibrosis (CF), a serious genetic disease that afflicts roughly 30,000 Americans, patients produce thick, dry mucus in their lungs that is hard to cough up and provides an ideal breeding ground for bacterial infections. The researchers are now investigating whether blocking the carbohydrate from binding to a specific protein would prevent the resulting biofilm from becoming tougher. If so, it would be a good target for future therapies, making the biofilm more vulnerable to the host's own immune system. This new perspective has the potential to improve the lives of a lot of people. The published paper was also covered on the Cystic Fibrosis News Today website. The research was funded by the University of Texas at Austin, ExxonMobil and grants from the Human Frontiers Science Program and the National Science Foundation.

After Advanced LIGO's recent direct observation of gravitational waves for the first time it becomes apparent that in order to make the transition from detection to meaningful observation and analysis of gravitational wave events precision calibration of the detectors is required. For the analysis after the detection of the gravitational waves from the mergers of binary black hole systems accurate calibration of the output of these detectors was crucial for the observation of these events and the extraction of parameters of the sources. This article, with co-authors Darkhan Tuyenbayev (UTRGV graduate student) and Dr. Volker Quetschke among other LIGO researcher, was chosen for the cover and as feature article of Review of Scientific Instruments. The article describes the photon calibrator systems that were completely redesigned for Advanced LIGO that meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. The article describes the design, implementation, and operation of these Advanced LIGO photon calibrators that are currently providing fiducial displacements of the LIGO testmasses on the order of 10^-18m/vHz with accuracy and precision of better than 1%.

M.-H. Kim at UTRGV, N. Yu at Columbia Univ., and S. Zhang at Harvard Univ. designed for the first time functional flat lenses for mid-infrared light with high efficiency and near diffraction-limited focusing. This work was performed in parallel with the first design of functional flat lenses at visible wavelengths by the Capasso group, Harvard Univ. [M. Khorasaninejad et al., Science 352, 1190-1194 (2016)]. These studies show that conventional bulk lenses can be replaced with metasurface lenses by overcoming the low power efficiency problem, and show promise for commercial applications such as camera lenses for smart phones and miniature lenses for health care and diagnosis applications.

We describe an alternative approach to the analysis of gravitational-wave backgrounds, based on the formalism used to characterize the polarization of the cosmic microwave background. In contrast to standard analyses, this approach makes no assumptions about the nature of the background and so has the potential to reveal much more about the physical processes that generated it.

Fermi-normal (FN) coordinates provide a standardized way to describe the effects of gravitation from the point of view of an inertial observer. These coordinates have always been introduced via perturbation expansions and were usually limited to distances much less than the characteristic length scale set by the curvature of spacetime. For a plane gravitational wave this scale is given by its wavelength which defines the domain of validity for these coordinates known as the long-wavelength regime. The symmetry of this spacetime, however, allows us to extend FN coordinates far beyond the longwavelength regime. Here we present an explicit construction for this long-range FN coordinate system based on the unique solution of the boundary-value problem for spacelike geodesics.

Nanoenergetic systems also known as metastable intermolecular composites (MIC) have various potential applications as propellants, explosives, and primers. The development of novel MIC systems, their design, synthesis and fabrication procedures are critical for national security and it was recognized as a significant addition to support of changing force structure for advanced weapons platforms. Our research at UTB focuses on developing a framework of principles for design and fabrication of nano-tailored highly energetic systems and nanoenergetic gas generators (NGG) for advanced energetic platforms. This involved a systematic study of physics based knowledge in energy release, shock waves and pressure discharge needed to enhance the performance and functionality of novel high density energetic systems.

Galaxies appear simpler than before by Disney et al. The image shows a montage of colored images of a dozen galaxies (huge whirlpools of stars in space) drawn from our survey of the universe, which is the subject of the letter. As well as being very beautiful they have considerable scientific interest too because they show a wider variety of galaxies than it has been possible to portray before. Hitherto galaxies were found optically, and hence tended to look rather like one another. These, however, were picked up in a radio survey and imaged only afterwards. Consequently they exhibit a much wider range of colors, shapes and surface brightnesses. Intriguingly some of them, although close-by in cosmic terms, are almost, but not quite, invisible. We believe both astronomers and laymen will find them fascinating. Copyright belongs to one of the co-authors, Andrew West.

Although predicted by S. Rytov more than sixty years ago the experimental proof that radiative heat transfer can be exponentially improved by reducing the gap between two surfaces of different temperature was only recently demonstrated for macroscopic objects with a geometry that can be compared with theoretical predictions. The scientists from the University of Florida and the University of Texas at Brownsville demonstrated good agreement between theoretical prediction and measurement. When an "infinite" warm surface is separated from a cooler one by a vacuum gap, the rate of radiative heat transfer between the two shouldn't depend on the size of the gap. According to theory, though, this picture doesn't hold when the surfaces are sufficiently close. In the paper "Near-Field Radiative Heat Transfer between Macroscopic Planar Surfaces" (Phys. Rev. Lett. 107, 014301, 2011), the scientists focused on a straightforward planar geometry. The heat transfer between two parallel square sapphire plates, each about two inches on a side, was measured for separations from a 0.1 mm down to only a few microns. A pronounced increase in heat transfer is seen as the gap between the plates is reduced following the theoretical predictions. In principle, near-field heat transfer could be used to control the temperature of an object without ever contacting it. This is an interesting possibility for cooling the sensitive mirrors in future gravity wave detectors.

We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir effect of the electromagnetic field and possible experiments to measure the time-dependent Casimir force are discussed.

Using recent data from the LIGO interferometers, LIGO scientists have been able to constrain the fractional energy density in gravitational waves to < 6.9 x10^-6 (at 95% confidence) in a ~100 Hz band around 100 Hz. This number improves on indirect limits on the gravitational wave background obtained from the relative abundance of light elements in the very early universe (Big Bang Nucleosynthesis). The attached figure shows various limits on the gravitational wave background and predictions from three different models (inflation, pre-Big Bang cosmology, and cosmic strings). The indirect limits are from Big Bang Nucleosynthesis and the Cosmic Microwave Background; the direct limits are from the LIGO S4 and S5 science data (see attached paper), and from pulsar timing data. Projected limits from the advanced LIGO detectors, the CMB Planck satellite mission, and the proposed space-based interferometer LISA are also shown.

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