December 8, 2017. 3:30PM. Bigelow Physics Building 102. Ho-kwang Mao. Solids, Liquids, and Gases Under High Pressure.

Pressure has long been recognized as a fundamental thermodynamic variable, but its application was previously limited by the available pressure vessels and probes. The development of multi-megabar pressure vessels and a battery of associated in-laboratory and synchrotron techniques at the turn of the century have opened a vast new window of opportunities. With the addition of the pressure dimension, we are facing a new world with an order of magnitude more materials to be discovered than all that have been explored at ambient pressure. Pressure drastically and categorically alters all elastic, electronic, magnetic, structural, and chemical properties, and pushes materials across conventional barriers between insulators and superconductors, amorphous and crystalline solids, ionic and covalent compounds, vigorously reactive and inert chemicals, etc. In the process, it reveals surprising high-pressure physics and chemistry and creates novel materials. I will describe the principles and methodology used to reach ultrahigh static pressure, the in situ probes, the physical phenomena to be investigated, the long-pursued goals, the surprising discoveries, and the vast potential opportunities. Examples include the recent advances and surprising findings in high-pressure research of hydrogen, oxygen, iron, and carbon. Overall, this review demonstrates that high-pressure research is a new dimension in physics, chemistry, Earth and materials sciences.

November 30, 2017. 7:30PM. Bigelow Physics Building 102. Shane L. Larson. Whispers from the Cosmos: The Dawn of Gravitational Wave Astronomy.

The Russell Frank Astronomy Lecture Series
UNLV Department of Physics & Astronomy

Whispers from the Cosmos:
The Dawn of Gravitational Wave Astronomy

Professor Shane L. Larson
Northwestern University

We tell the story of the discovery of gravitational waves (awarded the Physics Nobel Prize this year). These waves reveal what happens when two black holes collide, how the inner core of a star destroys itself during a supernova explosion, and how the graveyard of the galaxy is filled with the whisper of binary white dwarf stars that spiral together as they fade into oblivion. We will also look ahead to the future of this new branch of astronomy.

This talk is intended for a general audience including enthusiasts of all backgrounds and ages.

November 14, 2017. 2:00PM. BPB-217. Anna Childs. Exterior Giant Planet Effects on Terrestrial Architecture.

Masters defense

Terrestrial planet formation is a chaotic and violent process which is not fully understood. Prior to Kepler, Solar System observations were the basis for planet formation models. However, Kepler observations have shown that exoplanet systems are very different from our solar system, thus requiring a more complete planet formation model. With advancements in computational ability, N-body integrators, and collision models, we can explore planet formation by experimenting with simulations in different parameter space. Our Solar System has shown us that exterior giant planets can play a vital role in the shaping of the final terrestrial planet system. Our recent N-body simulations have explored the relationship between exterior giant planets of varying mass and size, and final terrestrial planet architecture. Understanding the relationship between the presence of giant planets and terrestrial system structure will help us interpret observation, and aid in the formulation of a general terrestrial planet formation model.

November 13, 2017. 3:00PM. BPB-217. Champika Sandamali Weerasooriya. Probing Broad Line Regions of Active Galactic Nuclei.

Ph.D. Defense

The broad line regions (BLR) of Type I Active galactic nuclei are too small to be spatially resolved even with the most powerful telescopes available. Observations suggest that the BLR gas is moving under the influence of the gravitational potential of a central super massive black-hole and responds to the variations in the ionizing continuum flux of the accretion disk. The continuum flux variations cause broad emission line variations with a time delay. Reverberation mapping campaigns seek to use this time variability to resolve the BLRs in the time domain instead of spatial domain, providing a way to infer geometry and kinematics of the BLR and calculate the mass of the central black hole. Numerous BLR models have been proposed over the years but only few of them are physically motivated. In this work, we examine the feasibility of constraining the parameters of such a physically motivated model; a disk-wind model of the BLR. We employ a Bayesian inference framework to compare predicted line light curves to an observed line light curve, using simulated data. A shortcoming of reverberation mapped data is that they may contain large gaps between consecutive observations. We have implemented a method and developed a code to evenly sample observed continuum light curves. One can then carry out, using observational data, an analysis similar to the one discussed above.

September 14, 7:00PM Bigelow Physics Building, BPB-102. University Forum Lecure: Mario Livio on Human Curiosity.

Human Curiosity

Thursday, September 14 - 7:00 PM Bigelow Physics Building, BPB 102
Please note the location change.

Mario Livio
Internationally known astrophysicist and bestselling author

The ability to ask "why?" makes us uniquely human. Curiosity drives basic scientific research, is the engine behind creativity in all disciplines from the arts to technology, and a necessary ingredient in every form of storytelling (literature, film, TV, or even a simple conversation) that delights rather than bores. In a fascinating and entertaining lecture, renowned astrophysicist and author Mario Livio surveys and interprets cutting-edge research in psychology and neuroscience that aims at exploring and understanding the origin and mechanisms of human curiosity. As part of his research into the subject, Livio examined in detail the personalities of two individuals who arguably represent the most curious minds to have ever existed: Leonardo da Vinci and Richard Feynman. He also interviewed 9 exceptionally curious people living today, among them linguist Noam Chomsky and the virtuoso lead guitarist of the rock band Queen, Brian May (who also holds a PhD in astrophysics), and presents fascinating conclusions from these conversations

Co-sponsored by the Department of Physics and Astronomy

Prof. Livio is an Adjunct Professor in Physics & Astronomy at UNLV. He is the author of numerous books and academic papers, including his latest: Why? What Makes Us Curious. Simon & Schuster. 2017. ISBN 978-1476792095. He was interviewed recently on NPR's Talk of the Nation Science Friday.

August 21, 2017. 9:00AM. BPB roof. UNLV Physics & Astronomy Eclipse activity.

The Aug 21, 2017 Eclipse

Around 9:00AM we'll set up a couple telescopes on the Bigelow Physics Building roof. The scopes will project an image of the Sun onto screens that can be safely viewed. We'll live stream one of the screens on to the net. The URL is: https://www.twitch.tv/horizonsci/

The scopes will be up from about 9AM to 12 noon which spans the whole eclipse maximum which will be at about 10:30 with 72 % coverage.

Drs. David Jeffery and Jason Steffen will be around to answer questions and demonstrate pinhole projection. Other students, faculty, and staff may also be on site to answer questions.

Postscript

Obviously, we didn't have an optimal day for viewing the eclipse in Las Vegas as a storm front moved through the valley. However, some time around 10:30AM clouds began clearing, glasses came out, a telescope was hastily set up and we had some quite good viewing from the roof and the area surrounding Bigelow Physics with "pinhole effects" from the tree canopy. Some images:

August 18, 2017. 2:00PM. BPB-217. Timothy Waters. Properties, Dynamics, and Spectral Signatures of Clouds in AGN.

Ph.D. Defense

Understanding the high-pressure behavior of transport properties has been a driving force in the study of materials under extreme conditions for well over a century being pioneered by P.W. Bridgman in the early 20th century. Research dedicated to the study of these properties leads to a variety of important applications: exploration of insulator to semi-conductor to metal structural and electronic phase transitions, correlation of structural phase transitions and the electronic properties along phase boundaries, testing validity of theoretical models, understanding the effects of chemical pressure, among a slew of other applications. This work has designed and developed a specialized sample cell assembly for use with a Paris-Edinburgh press capable of performing high-pressure and high-temperature (HP-HT) electrical resistance, Seebeck coefficient, thermal conductivity measurements alongside energy-dispersive X-ray diffraction and X-ray radiography imagining up to 6 GPa and 500�C to fully characterize the electrical, thermal, and structural properties of materials simultaneously at extreme conditions. This system has been installed at Argonne National Laboratory at the Advanced Photon Source at the Sector 16 BM-B beamline of the High-Pressure Collaborative Access Team and is now available to general users as a measurement technique. Application of this system has been applied to thermoelectric materials: PbTe, SnTe, TiCoSb, and TiNiSn. Thermoelectric materials provide a valuable means of converting waste heat into useful electrical energy and studying their HP-HT properties allows a better understanding and identification of greater efficiency through tuning of transport properties. The detailed discussion of the design and development of this system alongside the important results on the thermoelectric materials mentioned will be presented in this dissertation.

August 11, 2017. 10:00AM. BPB-217. Ye Li. Understanding Progenitors of Gamma-Ray Bursts with Multi-wavelength Properties.

Ph.D. Defense

Gamma-ray bursts (GRBs) are the most luminous explosions in the universe. They are generally classified into two types according to the durations of their Γ-ray emission. Progenitors of short-duration GRBs (SGRBs) are believed to be compact stars binaries (e.g., neutron stars and black holes; also known as Type I GRBs by their physical origin). For long-duration GRBs (LGRBs) they are thought to be originated from core-collapse of massive stars (Type II). However, the duration criterion is not always reliable. In this dissertation, I propose a multi-parameter method based on multi-wavelength data of GRBs to classify them by their physical nature, i.e., Type I or Type II. With a similar method, we search for SGRB-less X-ray transients with neutron star binaries as progenitors. The multi-wavelength studies of GRBs also allow for a study of the evolution of GRB population through the cosmic time.

July 10, 2017. 10:00AM. BPB-217. Jason Baker. Instrumentation and Measurement of Thermoelectric and Structural Properties of Binary Chalcogenides and Half-Heusler Alloys at Extreme Conditions Using a Paris-Edinburgh Press.

Ph.D. Defense

Understanding the high-pressure behavior of transport properties has been a driving force in the study of materials under extreme conditions for well over a century being pioneered by P.W. Bridgman in the early 20th century. Research dedicated to the study of these properties leads to a variety of important applications: exploration of insulator to semi-conductor to metal structural and electronic phase transitions, correlation of structural phase transitions and the electronic properties along phase boundaries, testing validity of theoretical models, understanding the effects of chemical pressure, among a slew of other applications. This work has designed and developed a specialized sample cell assembly for use with a Paris-Edinburgh press capable of performing high-pressure and high-temperature (HP-HT) electrical resistance, Seebeck coefficient, thermal conductivity measurements alongside energy-dispersive X-ray diffraction and X-ray radiography imagining up to 6 GPa and 500°C to fully characterize the electrical, thermal, and structural properties of materials simultaneously at extreme conditions. This system has been installed at Argonne National Laboratory at the Advanced Photon Source at the Sector 16 BM-B beamline of the High-Pressure Collaborative Access Team and is now available to general users as a measurement technique. Application of this system has been applied to thermoelectric materials: PbTe, SnTe, TiCoSb, and TiNiSn. Thermoelectric materials provide a valuable means of converting waste heat into useful electrical energy and studying their HP-HT properties allows a better understanding and identification of greater efficiency through tuning of transport properties. The detailed discussion of the design and development of this system alongside the important results on the thermoelectric materials mentioned will be presented in this dissertation.

March 30, 2017. 4:30PM. BPB-102. Prof. Isaac F. Silvera on Metalic Hydrogen

Hydrogen is the simplest and most abundant element in the Universe. Over 80 years ago Wigner and Huntington predicted that if solid molecular hydrogen was sufficiently compressed in the T=0 K limit, molecules would dissociate to form atomic metallic hydrogen. We have observed this transition at a pressure of 4.95 megabars. MH in this form has probably never existed on Earth or in the Universe; it may be a room temperature superconductor and is predicted to be metastable. Hydrogen makes up ~90% of the planet Jupiter. It is believed to occur as a layer of liquid metallic hydrogen surrounding Jupiter's core, responsible for Jupiter's magnetic field, with molecular hydrogen as the outermost layer. Descending through the atmosphere, a phase transition from liquid molecular to liquid atomic metallic hydrogen occurs as the pressure and temperature increase. This first-order phase transition to liquid metallic hydrogen is at intermediate pressures (~1-2 megabars) and temperatures of ~1000-2000 K. We have also observed this liquid-liquid transition, known as the plasma phase transition. We shall discuss the methods used to observe these phases of hydrogen at extreme conditions of static pressure in the laboratory, extending our understanding of the phase diagram of the simplest atom in the periodic table.

Prof. Isaac F. Silvera is the Thomas D. Cabot Professor of the Natural Sciences at the Lyman Laboratory of Physics at Harvard University

Prof. Lepp delivered the University Forum lecture: Supernova 1987A: Thirty Years Later

University Forum lecture looks back 30 years to the first time anyone since the days of Queen Elizabeth I was able to see a supernova with the naked eye.^*

Stephen H. Lepp is the chairman of UNLV's department of physics and astronomy. At 7:30 p.m. March 23, he will present "Supernova 1987A: Thirty Years Later" at the Marjorie Barrick Museum as part of the University Forum lecture series. Here, Lepp discusses what we learned from the first supernova visible to the naked eye in 400 years.

On Feb. 24, 1987, a supernova was discovered in the Large Magellanic Cloud. A supernova is an explosive end to a massive star. This supernova was bright enough to see with the naked eye, the first such in nearly 400 years and the first since the invention of the telescope. As such, this was the first bright supernova to be observed with modern scientific instruments. It was the first from which neutrinos were detected, the first in which molecules have been detected and the first where we have observations of the star before it blew up.

Stars begin their life in dense molecular clouds. These clouds, which exist between stars in our galaxy are basically star forming factories. Parts of the cloud can collapse to form dense objects which eventually burn hydrogen up to helium in the process of nuclear fusion. This is the most common configuration for stars, and almost all the stars you see in the night sky are undergoing this burning of hydrogen to helium.

Most of these stars are not massive enough to get temperatures high enough to burn anything beyond hydrogen, but the most massive stars will undergo a series of nuclear reactions burning elements all they way up to iron. Iron is the most tightly bound nuclei and so you cannot produce energy by converting iron to higher mass elements. The massive stars can undergo a processes called core collapse and the energy released out shines for a short time the entire galaxy. These explosions look like new stars and so were called nova or supernova.

In this talk we will cover the history of supernova observations and some interesting results from Supernova 1987A, along with some modern supernova research.

^{* From UNLV News Center}

Prof. Bing Zhang co-organized an Aspen meeting on Fast Radio Bursts

Prof. Zhang recently organized an Aspen Center for Physics conference "Fast Radio Bursts: New Probes of Fundamental Physics and Cosmology" on Feb.12-17, 2017. The conference hosted about 80 scientists from around the world to discuss the nature of Fast Radio Bursts, mysterious radio bursts discovered 10 years ago. The event was recently reported in the journals: Nature and Scientific American.

Prof. Zhaohuan Zhu Awarded Sloan Research Fellowship

Zhaohuan Zhu is the first UNLV scientist to earn fellowship for early career scholars considered ‘next generation of scientific leaders.’

From UNLV News by Shane Bevell.

Zhaohuan Zhu, assistant professor in the department of physics and astronomy, has been named a 2017 Sloan Research Fellow. He is one of 126 researchers from 60 colleges and universities in the U.S. and Canada – and the first UNLV scientist – to be awarded the prestigious fellowship.

Awarded annually since 1955 by the Alfred P. Sloan Foundation, the fellowships honor early-career scholars whose achievements mark them as the next generation of scientific leaders.

Zhu’s research focuses on the origin of Earth and other planets. By using powerful supercomputers and sophisticated numerical codes, he simulates how Earth formed billions of years ago. These computer simulations can be compared with the latest observations of young forming stars and planets to reveal the secrets of how planets are born around young stars.

“The Sloan Research Fellows are the rising stars of the academic community,” said Paul L. Joskow, President of the Alfred P. Sloan Foundation. “Through their achievements and ambition, these young scholars are transforming their fields and opening up entirely new research horizons. We are proud to support them at this crucial stage of their careers.”

Zhu received his M.S. and Ph.D. from the University of Michigan and was a postdoctoral researcher and Hubble Fellow at Princeton University before coming to UNLV last summer.

He was attracted to UNLV by its Top Tier initiative as well as the brilliant minds in the physics and astronomy department. “The research environment here is extremely active and stimulating,” Zhu said. “Additionally, my research expertise fits well in the department, and I can collaborate with almost every faculty member in the astronomy program. Another factor that attracted me here is the powerful supercomputer at the UNLV National Supercomputing Institute. My research relies on computing resources, and not every university has such powerful computers.”

The most interesting thing about the field, Zhu said, is that only recently have telescopes finally allowed researchers to image young forming planets in distant stellar systems. “The field progresses so fast and exciting new discoveries are made all the time, which I couldn’t imagine as a graduate student. Seeing planet formation in action is like seeing the birth of our Earth billions of years ago.”

Fellows receive $60,000 to further their research. The award is open to scholars in eight scientific and technical fields—chemistry, computer science, economics, mathematics, computational and evolutionary molecular biology, neuroscience, ocean sciences, and physics. Candidates must be nominated by their fellow scientists and winning fellows are selected by independent panels of senior scholars on the basis of each candidate’s independent research accomplishments, creativity, and potential to become a leader in his or her field.

“I am extremely honored to receive the Sloan Fellowship,” Zhu said. “I hope that this award will attract great students and scientists to our department and UNLV. With the support of the fellowship, I am looking forward to a productive future.”

Past Sloan Research Fellows include many towering scientific figures, including physicists Richard Feynman and Murray Gell-Mann, and game theorist John Nash. Forty-three former fellows have received a Nobel Prize in their respective field, 16 have won the Fields Medal in mathematics, 69 have received the National Medal of Science, and 16 have won the John Bates Clark Medal in economics, including every winner since 2007.

Spring 2017 Russell Frank Astronomy Lecture Announced

This semester's Russell Frank Astronomy Lecture will take place 7:30PM, Thursday March 9, 2017 in the Bigelow Physics Building room 102 at UNLV.

Professor Peter Mészáros from Penn State University will present: The Highest Energy Cosmic Rays: Messengers from the Deep Universe.

The highest energy cosmic rays are single atoms with the energy of a pistol bullet, hitting the Earth from outer space at the rate of one per century per square mile. Their energy greatly exceeds the energies reached by the largest terrestrial accelerators. These particles probably arise from giant explosive events associated with black holes. We will review the growth of cosmic ray physics from its inception to the latest multi-million dollar experiments, and discuss the recent intellectual and computational efforts which have greatly increased our understanding.

This talk is intended for a general audience including enthusiasts of all backgrounds and ages.

Prof. Qiang Zhu Published in Angewandte Chemie

Qiang Zhu recently had a research paper published in Angewandte Chemie. The paper, titled "The Structure of Glycine Dihydrate: Implications for the Crystallization of Glycine from Solution and Its Structure in Outer Space," looks at long-term puzzling crystal structure determination of glycine at low temperature and discusses its nucleation mechanism and possible existence in exoplanets.