Einstein's theory of gravity opened Pandora's box of warped spacetime in 1915, and out popped the black hole, confusing and delighting (or maddening) physicists ever since. In the early 1970's it was discovered that black holes have entropy and temperature, and decay by Hawking radiation like radioactive whirlpools in the spacetime river. Two persistent puzzles have resulted from this discovery: the information paradox and the transPlanckian problem. To bring some of this down to earth, Unruh in 1980 conceived of a black hole analog, formed by a quantum fluid, which might one day be studied in a laboratory. That day has now come...probably. In the last few years, Jeff Steinhauer has carried out a number of experiments on Bose-Einstein condensates of rubidium atoms, configured to emulate a black hole, and reported on the observation of thermal phononic Hawking radiation and its quantum entanglement with phonons inside the sonic black hole. In this colloquium I will describe these ideas and experiments, as well as simulations that have been carried out in order to help understand what has so far been observed.

 

The discovery of the Higgs Boson by the ATLAS and CMS experiments at the Large Hadron Collider (LHC) in Geneva, Switzerland, was one of the most important and exciting moments in particle physics. The field of particle physics has  transitioned to a new phase that presents us with a new opportunity to gain a deeper understanding of the fundamental nature of matter and our universe. I will discuss some of these implications, which inform the efforts to figure out  the roadmap of particle physics in the coming decades. Starting around 2026, the High-Luminosity LHC (HL-LHC) will deliver proton-proton collisions at a center-of-mass energy of \sqrt{s} = 14 TeV. I will summarize the studies from a comprehensive campaign mounted in 2018, to understand the physics reach of the experiments at the HL-LHC and a possible higher energy LHC (HE-LHC) at 27 TeV. 

 

 

Bright sources of x-rays, such as synchrotrons and x-ray free electron lasers (XFEL) are transformational tools for many fields of science. They are used for biology, material science, medicine, or industry. Such sources rely on conventional particle accelerators, where electrons are accelerated to gigaelectronvolts (GeV) energies. The accelerating particles are also wiggled in magnetic structures to emit x-ray radiation that is commonly used for molecular crystallography, fluorescence studies, chemical analysis, medical imaging, and many other applications. One of the drawbacks of synchrotrons and XFELs is their size and cost, because electric field gradients are limited to about a few 10s of MeV/M in conventional accelerators.

This seminar will review particle acceleration in laser-driven plasmas as an alternative to generate x-rays. A plasma is an ionized medium that can sustain electrical fields many orders of magnitude higher than that in conventional radiofrequency accelerator structures. When short, intense laser pulses are focused into a gas, it produces electron plasma waves in which electrons can be trapped and accelerated to GeV energies. This process, laser-wakefield acceleration (LWFA), is analogous to a surfer being propelled by an ocean wave. Betatron x-ray radiation, driven by electrons from laser-wakefield acceleration, has unique properties that are analogous to synchrotron radiation, with a 1000-fold shorter pulse. This source is produced when relativistic electrons oscillate during the LWFA process.

An important use of x-rays from laser plasma accelerators we will discuss is in High Energy Density (HED) science. This field uses large laser and x-ray free electron laser facilities to create in the laboratory extreme conditions of temperatures and pressures that are usually found in the interiors of stars and planets. To diagnose such extreme states of matter, the development of efficient, versatile and fast (sub- picosecond scale) x-ray probes has become essential. In these experiments, x-ray photons can pass through dense material, and absorption of the x-rays can be directly measured, via spectroscopy or imaging, to inform scientists about the temperature and density of the targets being studied.

Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344, supported by the LLNL LDRD program under tracking code 13-LW-076, 16-ERD-024, 16-ERD-041, supported by the DOE Office of Fusion Energy Sciences under SCW 1476 and SCW 1569, and by the DOE Office of Science Early Career Research Program under SCW 1575.