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2009 - 2010 Academic Year Colloquium Series
Thursday, March 19, 2009 - WMAP and Beyond
Dr. David Spergel, Princeton University
When: 4:00 PM
Where: Mendel 102
Refreshments will be served at 3:30 PM
The Wilkinson Microwave Anisotropy Probe (WMAP) has made an accurate full-sky
measurement of the microwave background temperature and polarization
fluctuations. These measurements probe both the physics of the very early
universe and the basic proprties of the universe today. The WMAP measurements
rigorously test our standard cosmological model and provide an accurate
determination of basic cosmological parameters (the curvature of the universe,
its matter density and composition). When combined with other astronomical
measurements, the measurements constrain the properties of the dark energy and
the mass of the neutrino. The observations also directly probe the physics of
inflation: the current data imply that the primordial fluctuatiuons were
primarily adiabatic and nearly scale invariant.
Many key cosmological questions remain unanswered: What happened during the
first moments of the big bang? What is the dark energy? What were the properties
of the first stars? I will discuss the role of on-going and future CMB
observations in these key cosmological questions and describe how the
combination of large-scale structure, supernova and CMB data can be used to
address these questions.
Thursday, March 26,2009 - How quickly do planets form? Studying protoplanetary
disk dispersal to constrain planet formation models
Dr. Eric Jensen, Swarthmore College
When: 4:00 PM
Where: Mendel 102
Refreshments will be served at 3:30 PM
More than 80% of Sun-like stars are surrounded at birth by orbiting disks of gas
and dust like the one that formed the planets in our solar system. Most of these
stars have lost any observable trace of this protoplanetary material by an age
of three million years, much shorter than the commonly-cited theoretical
timescale of tens of millions of years for the formation of giant planets. Have
these stars already formed planets on a much shorter timescale? Or does rapid
disk dispersal mean that planet formation is a rare event? I will discuss my
studies of disk evolution around young stars, and how these data may give us
insight into planet formation mechanisms. In particular, I will focus on DoAr
21, a low- mass star that has already lost its disk at an age of less than 1 Myr,
but which is still illuminating circumstellar gas with intense UV radiation; and
on lithium depletion in low-mass stars which may help us identify young stars of
planet-forming age that are far from known star-forming regions.
2008 - 2009 Academic Year Colloquium Series
December 4, 2008 - Borexino
When: 3:30 PM
Where: Mendel 154
Refreshments at 3:00 PM
Cristiano Galbiati, Department of Physics, Princeton University
The Borexino Solar Neutrino Detector at Gran Sasso Labs (Italy) is a low energy
solar neutrino detector operating since 2007 at Gran Sasso, with 300 tons of
liquid scintillator serving as an active target. The extremely low background
achieved in the target allowed the first real time observation of low energy
solar neutrinos, below the natural radioactivity barrier. I will report on
recent results from Borexino and their implications on neutrino physics and
oscillations.
November 13, 2008 - Particle Physics
Puzzles for the LHC
When: 3:30 PM
Where: Mendel 154
Refreshments at 3:00 PM
Evelyn Thomson, Department of Physics and Astronomy, University of Pennsylvania
I will explain the motivation for the Large Hadron Collider and discuss the
status of the commissioning of both the LHC and the giant ATLAS particle
detector. ATLAS will take digital pictures of the particles from LHC collisions.
I'll explain the interpretation of this information and how it could lead to
discovery of the missing piece of the standard model of particle physics, the
Higgs boson, or to discovery of particles and dimensions beyond the standard
model.
October 30, 2008 - The Rising of a Giant
Collider
When: 3:30 PM
Where: Mendel 154
Refreshments served at 3:00 PM
Chris Tulley, Department of Physics, Princeton University
On Sept 10th of this year the Large Hadron Collider (LHC) succeeded to circulate
proton beams in both directions around its 27 kilometer circumference. The ring
operated with all magnets superconducting at 1.9K and in the following week, the
radio-frequency acceleration system was commissioned. Shortly after, an incident
occurred in the magnet/cryostat systems that disabled sector 34 of the ring,
prompting an early shutdown of the LHC until late Spring of 2009. The successes
and failure of 2008 startup will be described for both the accelerator and the
Compact Muon Solenoid (CMS) experiment. There are many predictions for what new
physics lies ahead at the 14 TeV energy scale. I will present the goals for the
2009 run and the approach being taken to search for unknown new physics.
October 23, 2008 - Revealing the
mysteries of water by first-principles approach
When: 3:30 PM
Where: Mendel 154
Refreshments served at 3:00 PM.
Krzysztof Szalewicz, Department of Physics and Astronomy, University of Delaware
April 11, 2008 - A New Look at the
Proton and Neutron
When: 4:30 PM (Follows Sigma Pi Sigma induction ceremony at 4:00 PM)
Where: Mendel 102
Refreshments will be served.
Gerald A. Miller, Department of Physics, University of Washington
Recent electron scattering measurements have revealed unexpected features of the
proton and neutron wave functions. I discuss recent work revealing that the
proton is unlikely to have a spherical shape. Furthermore, the charge density of
the neutron is negative at its center.
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