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Colloquia

2015

Nnaturalness

Nima Arkani-Hamed (Institute for Advanced Study, Princeton)

About the speaker:Nima Arkani-Hamed is one of the top world-leaders in high energy theoretical physics. His research spans a wide range of subjects, fromparticle phenomenology to the geometry of scattering amplitudes. After finishing his PhD at Berkeley in 1997 and a 2-year postdoc at SLAC, Arkani-Hamed became faculty at Berkeley before joining Harvard as a professor. In 2008 Arkani-Hamed became a permanent member of the Institute for Advanced Study in Princeton. His awards are numerous and include the Sloan Fellowship, Packard Fellowship, American Academy of Arts and Sciences member, the 2003 Gribov Medal from the European Physical Society, the 2008 Raymond and Beverly Sackler Prize in Physics, and the 2012 Fundamental Physics Prize.

In this MCTP colloquium, Arkani-Hamed will discuss recent ideas to solve the Naturalness Problem in particle physics.

 

2014

"The Groundbreaking Discovery of Gravitational Waves from Inflation in the BICEP2 Cosmic Microwave Detector"

Katherine Freese (University of Michigan) and Jeff McMahon (University of Michigan)

Monday, April 21st, 2014, 340 WH, 5:10-6:10pm

ABSTRACT: Cosmology has just had a major discovery: gravity waves from the early Universe. The Cosmic Microwave Background polarization experiment BICEP2 has announced detection of B-modes, which can be explained as the gravitational wave signature of inflation.  We will discuss how these were found and their significance for cosmology.  This discovery, if confirmed in future data sets, is a “smoking gun” for inflation. Further, when combined with data from the Planck satellite, thousands of inflation models have now been ruled out. Remaining simple models are few, and include natural inflation and quadratic potentials. Natural inflation uses “axions” as the inflaton, where the term “axion” is used loosely for a field with a flat potential as a result of a shift symmetry.  That inflation could be so dramatically confirmed so quickly as a theory of the earliest Universe comes as a great surprise.

2013

"The Contribution of Planck to Cosmology"
Graca Rocha (Jet Propulsion Laboratory at Caltech)
340 West Hall on Thursday, April 18 from 3-4 pm 

On 21st of March of 2013, the ESA, NASA and the Planck collaboration announced the first cosmological results together with the data delivery and twenty eight scientific papers. This talk will give an overview of the main cosmological results from Planck presented in these twenty eight papers. The Planck satellite unveiled the most detailed and accurate map of the cosmic microwave background (CMB) --- the relic radiation from the Big Bang. Planck data confirms that the Universe is well described by a simple model in that it is fully defined by six key cosmological parameters. The Universe is older than expected, is expanding more slowly, has more dark matter and less dark energy than previously thought. Furthermore Planck puts stringent constraints on several models of Inflation (a period of exponential expansion of the Universe). With Planck data there is no evidence so far for a dynamical dark energy; no evidence for new types of ultralight particles such as neutrinos; no evidence for time-variation of fundamental constants such as 'fine-structure constant'; it also sets upper limits in the tensor-to-scalar ratio and finds that the fluctuations in the temperature of the CMB are very random (Gaussian). Some peculiar features 'anomalies' are observed in Planck maps, including the 'cold spot' (a spot extending over a patch of sky that is larger than expected) and the hemispherical asymmetry (i.e the two halves of the sky look different). These feature are unexpected in the context of the standard model.

2008

 

Saul Teukolsky (Cornell) “Black Holes and Gravitational Waves”

Thursday, April 3rd, 2008

1:00 – 2:00 PM, 340 West Hall 


Gravitational wave detectors like LIGO are poised to begin detecting signals. One of the prime scientific goals is to detect waves from the coalescence and merger of black holes in binary systems. Confronting such signals with the predictions of Einstein's General Theory of Relativity will be the first real strong-field test of the theory. Until very recently, theorists were unable to calculate what the theory actually predicts. I will describe recent breakthroughs that have occurred and that have set things up for an epic confrontation of theory and experiment.

 

 

Jonathan I Lunine (Prof. of Planetary Science and Physics) U. of Arizona

The Methane Hydrological Cycle on Titan

Thursday, March 27th 2008

340 West Hall @ 4:00 PM

 

2007

"Enceladus: An Active Ice World"

Professor John Spencer (Southwest Research Institute)

340 WH on Thursday September 27th from 4-5pm


The Saturn-orbiting Cassini spacecraft has discovered ongoing geological activity on Saturn's small (500 km diameter) moon Enceladus, making it the only known active icy body in the solar system. Tidally-generated heat powers a series of jets of ice particles, water vapor, and other gases issue from warm fractures close to Enceladus' south pole. Much of the gas and dust is ejected at speeds exceeding Enceladus' escape velocity, producing a dust and gas cloud that dominates Saturn's middle magnetosphere. Many questions remain about the nature of the tidal heat engine, the mechanism that produces the jets, and in particular about the possibility of liquid water, and other requirements for life, in the interior of Enceladus. A series of eight more flybys of Enceladus by the richly-instrumented Cassini spacecraft may provide answers to some of these questions.

2006

Inflation After WMAP 

Professor Paul Steinhardt (Princeton University)

May 18, 2006

Roughly twenty-five years after they were first established, five of the six milestone tests of inflationary cosmology have been passed. This talk will explain how the tests emerge from the inflationary model; why the most recent test, the detection of a tilt reported by the WMAP team a few months ago, is perhaps the most important to date; and why the sixth milestone test that lies ahead is now especially critical. Having pointed to the successes, the talk will then turn to disturbing developments in inflationary theory in the intervening twenty-five years that suggest the need for a major revision or perhaps a radical alternative.

What Does Quantum Field Theory Have In Common With Quantitative Marketing of Automobiles? 

Dr. Suzhou Huang (Ford Research and Advanced Engineering) 

March 30, 2006

The speaker will use his personal experience of transitioning from a theoretical physicist to a marketing scientist to answer the question posed in the title. Similarities and differences in these seemingly very distinct professions will be contrasted from perspectives ranging from the general ability to translate a specific problem into mathematical equations to the techniques adopted to derive appropriate solutions. In addition, the audience will get a glimpse of what are involved in quantitative marketing in the auto industry: financial risk management, revenue management, used-car auction, etc.Co-sponsored by the Center for the Study of Complex Systems (CSCS) and Life After Graduate School seminar series

"Enceladus: An Active Ice World"

Professor John Spencer (Southwest Research Institute)

340 WH on Thursday September 27th from 4-5pm

The Saturn-orbiting Cassini spacecraft has discovered ongoing geological activity on Saturn's small (500 km diameter) moon Enceladus, making it the only known active icy body in the solar system. Tidally-generated heat powers a series of jets of ice particles, water vapor, and other gases issue from warm fractures close to Enceladus' south pole. Much of the gas and dust is ejected at speeds exceeding Enceladus' escape velocity, producing a dust and gas cloud that dominates Saturn's middle magnetosphere. Many questions remain about the nature of the tidal heat engine, the mechanism that produces the jets, and in particular about the possibility of liquid water, and other requirements for life, in the interior of Enceladus. A series of eight more flybys of Enceladus by the richly-instrumented Cassini spacecraft may provide answers to some of these questions.

2005

Comments on Time Variation of Fundamental Constants

Michael Duff (University of Michigan)

April 20, 2005


The possible time variation of dimensionless fundamental constants of nature, such as the fine-structure constant, is a legitimate subject of physical enquiry. However, contrary to recent claims in Physical Review Letters, Physical Review, Nature, Physics World, Scientific American, New Scientist, New York Times, CNN etc, the time variation of dimensional constants such as the speed of light, Planck's constant or Newton's constant, has no operational meaning, depending as it does on a subjective choice of units


The Principles of Disorder and Their Applicability to Condensed Matter Physics, Neurophysiology and Cosmology

Stan Ovshinsky (Energy Conversion Devices, Michigan)

January 11, 2005


Periodicity and crystal structure have been the basis of condensed matter. The tyranny of the lattice has not only produced a revolution in the invention of the transistor but has also been a serious constraint to new physics. I will describe how amorphous and disordered materials provide many degrees of freedom to synthesize new materials so that multi-elemental atomic and orbital engineering can generate new basic physical, chemical, and electronic mechanisms.For the first time, one can emulate biological neurosynaptic activity with a non-biological analog that provides cognitive functions. The nanostructure device which accomplishes this is based upon unique reversible phase change mechanisms. The universe has evolved based upon symmetry breaking and phase changes, hence the cosmological relationship. Such phase changes and their related devices have initiated a fundamental change in the computer, optical and electronic industries. The principles that we use in designing amorphous and disordered materials have permitted us to demonstrate that our Ovonic cognitive computer can also perform functions at room temperature similar to that of the proposed quantum computer. Our work shows that there are new unifying principles that we utilize in amorphous and disordered materials that span scientific disciplines and help break down the barriers between theoretical and applied physics. For example, their use in the energy field has enabled hybrid vehicles and initiated the hydrogen economy just as they have changed optical and electrical memories in the field of information.

2004

What is the Cosmological Significance of a Discovery of Dark Matter Particles?

Jacob Bourjaily (University of Michigan)

November 23, 2004


There are many reasons to suspect that our universe contains a large amount of cold dark matter. The most popular particle candidates for dark matter are weakly interacting massive particles (wimps). These particles are being searched for directly and indirectly by dozens of experimental groups throughout the world. Let us suppose that wimps are unambiguously detected in one or more of these experiments. Such a discovery would be an undeniable triumph of particle cosmology. Would it imply that we have solved the dark matter problem? Unfortunately, there is no reason to expect that dark matter is composed of a single type of particle. Furthermore, it is easy to provide examples of dark matter models (e.g. in supersymmetry) where nearly identical detector signals correspond to extremely different relic densities. Therefore, the density of wimps must be determined before their cosmological relevance is established.I will present ways to differentiate between many of the candidate dark matter particles. I will offer a general method to estimate (or determine) the density of the Lightest Supersymmetric Particle (LSP) within the most general minimally supersymmetric standard model.


The Gravitational Wave Universe

Bernard Schutz (Max Planck Institute for Gravitational Physics)

November 9, 2004


The LIGO gravitational wave project and its international partners will soon enter a phase of full-time observing. In a few years an upgrade will improve LIGO detectors' sensitivity by a factor of 10. Soon afterwards, the joint ESA-NASA space detector LISA will embark on a 10-year search for giant black holes, becoming the first detector to be limited by source confusion rather than detector noise. Already something like a thousand scientists spend some or all of their time developing these projects. What have they accomplished so far? What is left to do? What can we expect to learn with these instruments? What potential do they have to reveal aspects of the Universe that we know nothing about at present? I will address these and related questions using the most recently published detector data and theoretical studies of gravitational wave sources.


Unveiling the Universe 

Joseph Silk (Oxford)

May 25, 2004


I will review the current situation with regard to dark matter, both baryonic and non-baryonic. I will discuss the implications for galaxy formation and the possibilities for detection of dark matter.


Event Horizons and the Generalized Second Law of Thermodynamics

Paul Davies

April 20, 2004


The association of entropy with black hole event horizons by Bekenstein and Hawking hinted at deep linkages between quantum field theory, gravitation and information. Attempts have been made to sharpen this linkage through concepts such as gravitational entropy and the holographic paradigm. In this lecture I will present some new results that seek to clarify the relationship between black hole and cosmological horizon entropy, and extend the boundaries of the generalized second law of thermodynamics.


CORE: Frustrated Magnets, Charge Fractionalization and QCD

Marvin Weinstein (SLAC)

March 16, 2004


I will briefly explain the COntractor REnormalization group method (CORE) and show how it can be used to study various condensed matter systems. I then show how the same method can be used to map systems of massless free bosons, massless free and fermions interacting through gauge fields, into a class of generalized, highly frustrated anti-ferromagnets. I finally discuss the relation of these results to the lattice Schwinger model and QCD.


Exploring Young Brown Dwarfs

Ray Jayawardhana (University of Michigan Astronomy Department)

February 3, 2004


Brown dwarfs, which straddle the mass range between stars and planets, appear to be common both in the field and in star-forming regions. Their ubiquity makes the question of their origin an important one, both for our understanding of brown dwarfs themselves as well as for theories on the formation of stars and planets. I will present new results from a multi-faceted observational program that provide valuable clues to the formation and early evolution of sub-stellar objects. In particular, based on measurements of disk frequency in the infrared and accretion signatures in the optical, I will discuss whether young brown dwarfs undergo a T Tauri-like phase and if so how long that phase lasts. I will also show that surface gravities and effective temperatures of very low mass objects can be well determined from a multi-feature analysis of high-resolution spectra in comparison with the latest synthetic spectra. Combined with photometry and distance information, this allows us to derive the first mass and radius estimates for young substellar objects that are independent of theoretical evolutionary tracks. Our results are in good agreement with the track predictions, except for the coolest, lowest-mass objects, which appear both larger and less massive than the tracks predict. I will discuss the implications of these results.


Puzzle of Charge and Mass

Stuart Raby (Ohio State University)

January 19, 2004


Beginning with the seminal work of Rutherford, Geiger and Marsden in 1911, physicists have investigated the atom using particle beams (alpha particles, and protons) as probes. They developed new detection methods; the geiger counter, scintillators, cloud and then bubble chambers. This new paradigm for probing matter and new detectors lead to many discoveries. It is these principles and their logical extension which I will attempt to describe in this talk. It is these principles and their logical extension which I will attempt to describe in this talk

2003

Black Holes for the Curious Physicist (and Mathematician)

Malcolm Perry (University of Cambridge)

September 30, 2003


I will describe the basic properties of black holes, the uniqueness theorems, and the laws of black hole mechanics. This allows to progress to a description of the Hawking effect and black hole evaporation. then, I will briefly review the information paradox. Finally, I will comment about some of the string theory results that shed some light on the problems of semiclassical black hole theory.


Quantum Gravity With a Positive Cosmological Constant

Lee Smolin (Perimeter Institute)

May 20, 2003


Recent results of loop quantum gravity which concern the case of positive cosmological constant will be presented. These include the existence of an exact quantum state which is both an exact solution to the quantum field theory constructed from quantizing general relativity and has a good low energy limit which recovers quantum field theory on de Sitter spacetime. Related results to be discussed include the extension of the thermal properties of quantum fields in deSitter spacetime to full quantum gravity with a positive cosmological constant and the recovery of the horizon entropy and N bound. Predictions can also be derived for new and potentially observable phenemona coming from planck scale corrections to dispersion relations and quantum gravity corrections to inflaton potentials. Final, issues of quantum theory in cosmological spacetimes and in the presence of horizons are discussed and new proposals to resolve them based on relational approaches to quantum cosmology are described. The work to be described was done by and in collaboration with Chopin Soo, Hideo Kodama, Fotini Markopoulou, Laurent Freidel, Carlo Rovelli and Stephon Alexander.


The Birth of Flight Control: Flight Testing with the Wright Brothers

Gareth D. Padfield (The University of Liverpool, UK) 

James Bibby Professor of Aerospace Engineering 

May 2, 2003


The Wright Brothers achieved their goal through their innovations in flight control and the title of this lecture reflects the notion that their breakthrough was to invent flight control in a style that would shape all future aircraft, and enable them to progress to the first powered flight in 1903. The Wright Brothers were the first aeronautical engineers and first test pilots and 1902 was perhaps the most critical year in their work and the development of the aeroplane. The story of their invention in this centenary year is told through a description and assessment of the technical challenges faced by the Wrights, their unique approach to innovation and their dedication to their goals. The story is enhanced through the understanding gained from the development and testing of high-fidelity simulations of the Wright aircraft on the Liverpool Flight Simulator. Activities from this project will feature in the lecture, including wind tunnel tests, multi-body dynamic modelling, closed-loop control analysis and test flying.


Laws of Nature in Physics and Philosophy

Jessica M Wilson (Univeristy of Michigan)

April 22, 2003


I argue that certain hypotheses of contemporary fundamental physics support one philosophical account of laws of nature over another.

2001

Ann Arbor and Copenhagen: Goudsmit, Heisenberg and Bohr

Rudi Paul Lindner (History Department, University of Michigan)

November 27, 2001


During the Ann Arbor summer school of 1939 Samuel Goudsmit and others attempted to convince Werner Heisenberg to leave Germany. Heisenberg not only refused, but during World War II he played an active role in the German nuclear project. The drama Copenhagen, due to open in Detroit, reminds us of his equivocal position, as does a letter, soon to be released, that Niels Bohr wrote but did not mail after Heisenberg's famous visit to Copenhagen. This talk revisits Heisenberg's wartime role, Bohr's response, and Goudsmit's later reunion with his Ann Arbor guest.


Black Holes in String Theory

Finn Larsen (University of Michigan)

October 30, 2001


Black holes exhibit thermal properties when quantum theory is taken into account. The microscopic structure responsible for this behavior is quite mysterious. Recent advances in string theory has led to dramatic progress on this problem. The colloquium is an account of this development intended for non-experts.


M-Theory and the Brane World

James Liu (University of Michigan)

April 24, 2001


Much recent attention has been paid to the idea that our 3+1 dimensional universe may turn out to be a brane embedded in a higher-dimensional spacetime. In such brane world models, the extra dimensions are often assumed to be large and possibly even infinite in extent. In contrast, string theory, which for a long time has embraced extra dimensions, has traditionally taken them to be extremely small and unobservable. However the two cases are not as far apart as they may appear on the surface, as M-theory provides a basis for realizing large extra dimensions. I will first review some of the background of extra dimensions in M-theory and then explore possible connections between M-theory and the brane world.


Stochastic Ratchets

Charles Doering (University of Michigan, Math Dept.)

March 7, 2001


A ratchet is a device that can rectify nondirectional forces. In this talk we will discuss some elementary models of ratchets capable of rectifying statistically isotropic noise into directional motion. We'll describe some applications of these ideas in mesoscopic condensed matter physics and molecular biology, and discuss some (perhaps) unexpected features of the simplest models.