Applied Physics / Physics Colloquium

Applied Physics/Physics Colloquium

Topic: 
Cortical Vision from Emergent Global Dynamics
Abstract / Description: 

The confusing thicket of connections between neurons renders the brain a complex system. We have embarked on deducing how the subjective experience of vision emerges from the interaction of billions of neurons. Picking up mathematical tools from established studies of complexity, we infer network properties from the statistics of neural activity in cerebral cortex during visual processing. Specifically, I will present evidence for the notion that brain circuits self-organize to operate at a point of optimized signal processing, including during intense visual stimulation.


 

Refreshments in the lobby of Varian Physics at 4:15 pm.

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

 

Date and Time: 
Tuesday, January 12, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Effective Field Theory in Cosmology
Abstract / Description: 

Observational cosmology has made tremendous progress in the last couple of decades, allowing us to explore the beginning of the universe with unprecedented precision. Such exquisite measurements have now made us sensitive to non-linear corrections to the evolution of the density perturbations. In order to continue to address the mysteries of our universe with similar success, we have to be able to control these non-linearities. In this context, the effective field theory paradigm, which has been widely used in the context of particle physics, represents the ideal setup to explore and systematically study the signatures that come from interactions, and additionally to directly map what we are learning from data into theory. I will describe two recent applications of this paradigm to Cosmology: the Effective Field Theory of Inflation and the Effective Field Theory of Cosmological Large Scale Structures (EFTofLSS). The first example represents the general parametrization of fluctuations around an inflationary background, the earliest phase of our universe, and it allows us to study its most general signatures. The second example is in the context of the gravitational clustering of matter. In our universe matter perturbations are large on short distances and small on long distances: strongly coupled in the UV and weakly coupled in the IR. We formulate an effective description based on an IR fluid-like system that allows us to develop a perturbative expansion to describe weak matter clustering. I will discuss the formalism, the main results and successes so far, and how this research program is crucial for next generation cosmological experiments.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, January 19, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Black Holes from Cosmic Inflation
Abstract / Description: 

Spherical domain walls and vacuum bubbles can spontaneously nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the walls and/or bubbles form black holes with a wide spectrum of masses. For some parameter values, the black holes can serve as dark matter or as seeds for supermassive black holes at galactic centers. This mechanism of black hole formation is very generic and has important implications for the global structure of the universe. Black holes with mass greater than certain critical value contain inflating universes inside. The resulting multiverse has a very nontrivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, March 8, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Electromechanics: A New Quantum Technology
Abstract / Description: 

Devices that combined electricity with moving parts were crucial to the very earliest electronic communications. Today, electromechanical structures are ubiquitous yet under-appreciated signal processing elements. Because the speed of sound is so slow compared to the speed of light, they are used to create compact filter and clock elements. Moreover they convert force and acceleration signals into more easily processed electrical signals. Can these humble, apparently classical, objects exhibit genuinely quantum behavior? Indeed-by strongly coupling the vibrations of a micromechanical oscillator to microwave frequency electrical signals, a mechanical oscillator can inherit a quantum state from an electrical signal. This recent and exciting result heralds the development of a quantum processors or quantum enhanced sensors that exploit the unique properties of mechanical systems. Furthermore, quantum electromechanics provides a powerful and versatile way to bring ever larger, more tangible objects into non-classical regimes.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, March 1, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
The Genesis of General Relativity and its Formative Years
Abstract / Description: 

The conceptual revolution that Einstein started in 1907, when he introduced the equivalence principle and began his search for a comprehensive theory describing gravitation and inertia within a relativistic framework, was completed with the publication, on November 25, 1915, of his general theory of relativity. Immediately after its publication the theory was elaborated and controversially discussed by physicists, mathematicians, astronomers, and philosophers. During these formative years, the basic ideas and principles were refined, the first solutions of the field equations were derived and analyzed, and the cosmological consequences of the theory were debated. Einstein himself made further fundamental contributions to the development of his theory, exploring its consequences such as gravitational waves and cosmological models, and reinterpreting basic aspects of the theory.

On the hundredth anniversary of Einstein's monumental achievement, it is natural to look back at what we are celebrating and address such questions as: What guided Einstein on his road to general relativity? What guidelines had to be re-examined and even abandoned? Why did it take him eight years? Why did he reject every suggestion of an expanding universe? Why did he introduce the cosmological constant and why did he remove it? The lecture will describe Einstein's unique scientific odyssey, exploring these and other questions.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, February 23, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
On the Measurement of Gravitational Waves from the Merger of two Black Holes
Abstract / Description: 

Over a billion years ago, a binary black hole system enjoyed its last few orbits and collided, releasing three solar masses worth of energy into vibrations of spacetime: gravitational waves.

​Towards the end of the summer of 2015, the ​LIGO team was wrapping up the final touches on the recent upgrades to their interferometers and getting it ready to run. Early in the morning on September 14th, those waves from a billion years ago rippled through the earth and were recorded by the LIGO detectors.

This is the story of those waves and detectors.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, February 16, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 200

Applied Physics/Physics Colloquium

Topic: 
Can We Find 10 TeV Particles Using Sub Millihertz Spectroscopy? Looking for the Electron's Electric Dipole Moment in Trapped Molecular Ions
Abstract / Description: 

Any competent scientific editor will scribble "redundant terminology!" in the margin next to the phrase "10^{-15} femtometers". But that is indeed the current experimental upper limit on the distance between an electron's center-of-mass and its center-of-charge. There are several good reasons to imagine that these two locations might not be at exactly the same place inside this nominally "point particle." At JILA, we hope to improve the experimental limit by a factor of ten. If we see a nonzero value, that will be evidence for new particle physics at an interesting energy scale.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, February 9, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Batteries: Now and Future
Abstract / Description: 

Increased demands of batteries for applications in consumer electronics, electric vehicle and grid present opportunities and challenges for rechargeable batteries. This lecture will analyze the nature of energy storage, the existing technology and present the promising future batteries, which can have significantly higher energy density, lower cost, better safety and longer life. Novel battery chemistries and materials are key for a revolutionary change.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, February 2, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Observations of Cosmic Neutrinos with IceCube
Abstract / Description: 

The IceCube Neutrino Observatory at the US South Pole Station is a cubic-kilometer scale neutrino detector, using a billion tons of ultra-pure Antarctic ice as a Cherenkov radiator. IceCube detects over 100,000 neutrinos per year, at energies ranging from a few GeV to several PeV. Most of these are produced in the Earth's atmosphere, but at the highest energies we have discovered a neutrino flux of cosmic origin. Although their exact sources remain unclear, the level of this flux suggests that hadron accelerators produce a considerable fraction of the energy in the non-thermal universe. We will discuss the IceCube Observatory, the observations of high energy neutrinos, and their significance.


 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Winter 2015/2016, Committee: R. Blandford (Chair), T. Heinz, L. Hollberg, K. Irwin

Date and Time: 
Tuesday, January 26, 2016 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Neutrino Oscillations: Past, Present and Future
Abstract / Description: 
Neutrino oscillations had been one of the most successful stories in the history of particle physics. I will review the discovery of neutrino oscillation and confirmations afterwards. There are quite a number of neutrino experiments under operation now and many under planning. In particular, I will explain a reactor-based neutrino experiment, Daya Bay, for mixing angle theta-13 and its successor, JUNO experiment for the neutrino mass hierarchy.

 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Autumn 2015/2016, Committee: A, Linde (Chair), S. Chu, P. Hayden, M. Schnitzer, L. Senatore

Date and Time: 
Tuesday, November 10, 2015 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

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