Publications and Citations at Google Scholar
Physics Research Interests:
The main thrust of my research in High Energy Physics is to elucidate the strongly interacting sector of the Standard Model of elementary particle interactions (interactions of quarks and gluons and the phenomenology of mesons and baryons made up of these elementary particles) and probe signatures of new physics at the TeV scale using lattice Quantum Chromodynamics (Lattice QCD) . The observables calculated include the hadron spectrum, quark masses, chiral properties of hadrons, nucleon structure, nucleon electric dipole moment (nEDM), glueballs, decay constants, semi-leptonic form factors, form factors for rare radiative decays of B mesons, matrix elements of 4-fermion operators and their B parameters and QCD at finite temperature. To understand the QCD vacuum we have also investigated chiral symmetry breaking, restoration of U(1) axial symmetry at finite temperature and topology on the lattice.
Large scale simulations have been carried out since 1985 under the auspices of the DoE Grand Challenges awards and allocations of computing resources on national supercomputer centers. Simulations were first carried out on Crays and a number of parallel supercomputers including the Thinking Machines CM-2 and CM-5, the SGI Origin 2000 at the Advanced Computing Laboratory at Los Alamos, the Cray T3E at NERSC and commodity clusters. Current calculations are being done on leadership class supercomputers at national computing centers. At Los Alamos, I also contribute to the development of high performance parallel computing.
A colloquium titled Discovering elementary particles and determining their masses (5.6 MB pdf file LA-UR-03-6215) describes how elementary particles are identified and how their masses are determined in high energy experiments. It also discusses how simulations of lattice QCD are used to estimate the masses of quarks which are not seen as isolated states in nature.
Calculations of matrix elements of novel CP violating operators that arise in the effective field theory analysis of new physics at the TeV scale. The goal is to quantify their contribution to the neutron electric dipole moment and understand if they are large enough to explain baryogenesis. This work is being done as part of the CP Violation collaboration.
Papers formulating this project, results and the status of the calculations are given in
We are using Lattice QCD to calculate the matrix elements of quark bilinear quark operators between neutron and proton states. These matrix elements are needed to look for signatures of new physics at the TeV scale by relating theory to precision measurements of neutron decay distributions being done at Los Alamos, Oak Ridge and centers around the world. This work is being done as part of two collaborations: PNDME (Precision Neutron Decay Matrix Elements) collaboration and NME (Nucleon Matrix Elements) collaboration
Papers formulating this project, results and the status of the calculations are given in
Since 2006, Ron Soltz and I have been co-leading the HotQCD collaboration collaboration to understand QCD at finite temperature using lattice QCD. We are using the Asqtad, p4 and HISQ improved staggered actions developed by the MILC and RBC-Bielefeld collaborations to simulate (2+1) and (2+1+1) flavor QCD at finite temperature on the BlueGene Q at LLNL and supercomputers at Fermilab, ANL and at other centers. Our goal is to elucidate the nature of the chiral and deconfining transition and determine the QCD equation of state over the temperature range 150-700 MeV relevant to heavy ion experiments at RHIC and LHC. HotQCD publications on these topics include
Calculations of matrix elements of light cone operators within the proton state that shed light on the contribution of the angular momentum of quarks to the proton spin. Of particular interest is the extraction of the Sivers and Boer-Mulders distribution functions.
In addition to particle physics, I have also worked on determining the critical exponents of Statistical Mechanics systems, in particular the Ising and XY models. My favorite methods are Monte Carlo Renormalization Group and finite size scaling. Topcited papers include
Other Interest: Job Security, Automation, Population Growth, Migrtation and Threat to Democracy:
In the 2016 talk In a world with 10 billion people, what will 8 billion do? (4.5 MB pdf file. LA-UR-16-27101) I examine current developments in technology and automation (robots and AI) and their impact on the nature and numbers of jobs that will be valued and needed in the future. This prompted the question whether there will be sufficient numbers of high quality jobs created to prevent large sections of the population remaining in, and worse sinking into, generational poverty? I then ask the second question whether the current population and its growth is sustainable in an "iRobot" society, and how developed nations will deal with the increasing numbers of people desperate to migrate to them in search of a better life? Will new social contacts emerge in the iRobot era that distribute more equitably the gains of the few at the top to the global population? My contention is that if these challenges are not addressed in a timely fashion, Western/liberal democracy could be threatened in even the developed countries.
Other Interest: Energy Security:
Energy is key to development. The twentieth century was dominated by fossil fuels -- oil, coal and gas. Today we are faced with declining production of conventional oil in many parts of the world but new unconventional sources are being exploited. Natural gas is considered the bridge fuel and its use is growing. The world is dependent on unstable regions of the world for their oil and natural gas supplies and energy security remains a key driver of geo-politics. Equally important, the environmental impacts of burning fossil fuel are global and there is growing concensus regarding the urgency to address global warming. Current cumulative investment in fossil fuels already exceeds $40 trillion. Furthermore, China and India have hundreds of new coal fired power plants in planning and construction stages that will not be CO2 neutral and will continue to be in operation for the next 40 years. Such a large system will take a long time to change even under the best of circumstances. It is, therefore, important to plan, develop and transition to carbon neutral sources/technologies. At the same time we must ensure the availability of affordable energy for the global population so that development and opportunities are shared. Recent colloquia on this topic include
The Global Energy Observatory (GEO): Understanding the dynamics of change in energy systems
GEO is a free interactive website (a moderated Wiki) containing databases and tools developed collaboratively to make the global energy systems available to all interested readers. Our goal in building GEO is to collect, collate, manage and display data and integrate it with analysis tools to help people understand energy systems and their networks by performing real time analysis.
Other Interest: HIV/AIDS, Public Health and Education in the Developing World:
Since January 1999 I have been involved in developing educational material for accelerating the spread of awareness on disease prevention (in particular for HIV/AIDS), health care, education, and enviornmental among school students, industrial workers, villagers, and the public in general. Summary of my work in India can be found at AIDS Crisis in India. Based on my experiences and work in India and New Mexico, I have written a number of articles that are archived at MY WORK. In particular, a detailed analysis of the underlying reasons for the spread of HIV/AIDS in India, its consequences for development and security, and mitigation strategies is presented in the monograph Risky Sex, Addictions, and Communicable Diseases in India: Implications for Health, Development, and Security.
In a recent colloquium at Stanford and NREL, I make the connection between HIV/AIDS and the future of the poor, illiterate and marginalized populations and argue, using India as an example, why business as usual will not suffice, and why we need to help the poor in developing countries make the transition to the knowledge society (4.7 MB pdf file LA-UR-05-3139). Another talk at the University of Chicago discuses HIV, Empowerment, and how concerned people can help. (LAUR-07-3557)
Stopping the spread of HIV/AIDS is not just a matter of awareness, or of access to retroviral drugs, or of working health care systems, or of education, or of removing violence to women, or of GLT rights, or of providing job skills and jobs, or of good governance or of poverty. It is about all these issues and much more. Increasingly I believe that development requires and needs a holistic approach at all levels. To this end, a framework for a coupled systems analysis is presented in Five Global Grand Challenges. A related talk The Dynamics of change: India a case study analyzes the fast pace of change taking place globally and highlights four areas of priority that urgently need investment for accelerating the process of providing opportunities to the poor.