All posts by Jesse Rogerson

The 2007 Golden lion tamarin conference Abstracts

28 March 2009conference2007 conference, abstractsJesse Rogerson

Abstracts:

Alireza Rafiee
Quasar lifetime and Black Hole Spin Quasars seem to have a limited lifetime

They continuously accrete matter and gain angular momentum but the increase on radiative efficiency of that system remains limited to a physical upper bound. Using that physical barrier, we have estimated an upper limit for quasar lifetime.

Steve Beale
Measuring Bs mixing at the Fermilab Tevatron

Neutral Bs mesons (b-bar s) will spontaneously transform into their anti-particle (and visa versa) by a weak process known as mixing. Measurement of the mixing frequency provides an important constraint on the electroweak coupling of s and d quarks with the top quark. Presently, the only place where this measurement can be made is at the Fermilab Tevatron, a proton-antiproton collider with a center of mass energy of 1.96 TeV. The D0 detector is one of two collider detectors at Fermilab currently working to make this measurement. After a short overview of the Tevatron, the D0 Detector, and general mixing phenomenology, I will present the latest mixing measurement from D0.

Tzahi Yavin
Modelling Markets

In the last quarter of a century or so, the sophistication of the mathematical modeling of financial markets has witnessed a tremendous increase. In this talk I will briefly discuss one of the corner stones in this field, the Black-Scholes model, and how it is used to price options for stocks trading on the stock exchange.

Yan Sun
Density functional study of 13-atom transition-metal clusters and bimetallic A_4B_12 clusters

Min zhang
Global optimization of 13-atom 5d transition metals

We did structural global optimization for six 5d transition metals(Ta-Pt). Two optimization algorithms, Tabu Search in Descriptor Space(TSDS) and Simulated annealing (SA), were used and their performances were compared. Energy evaluation was done with PBE exchange-correlation functional implemented by VASP. Due to complexity of the multiplicities of transition metals, we did calculations with full relaxation of multiplicity. Amazingly, we found none of them had an icosahedral ground state structure. We compared thoroughly our results with previously reported structures. Calculations show that our results are the best. To rule out the difference could be introduced by choice of functional, we did local optimization for our results and structures reported by other researchers with LDA and PW91. The LDA and PW91 functionals give similar results to PBE and confirm that we found the best structures to date for these clusters.

Brynle Barrett
Interferometric Measurement of the Fine Structure Constant using Cold Rubidium

Atoms in an Atomic Fountain One of the most challenging questions in astrophysics today is to establish when and how the universe became (re)ionized. Although it is accepted that the overall process is well understood, and in spite of the observational and theoretical progress that have been made in the last few years, there are still many details that remain controversial and unsolved. At a redshift z ~ 6 we are approaching to the end of Epoch of Reionization, but the number of known quasars and galaxies close to this redshift is still very low, thus the uncertainties are large. To improve our knowledge of that fundamental epoch we need to find more high redshift sources. Here, I will briefly summarize some of the basic ideas on this topic and present the description of the data we are working on and the procedure we have followed.

Edward Ackad
Supercritical Collisions with no intial electrons Colliding two fully ionized

Uranium atoms can lead to pair creation, but solving for a collision with no initial electrons is not commonly done. I will show how it is possible to solve for this system and show results of current work were we can show the enhancement of the positron production due to the decay of supercritical resonance state for collisions with some nuclear sticking.

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The 2007 Golden lion tamarin conference

28 March 2009conference2007 conference, announcementJesse Rogerson

When: August 30th, 2007
Where: Ross S137 (Number 30 in York map)

To present a talk in the conference, please send an email to the president of the PAGE.
Attendance is free. We strongly encourage graduate students to participate this event.

Organizing Committee:

Alireza Rafiee arafiee@yorku.ca
Brynle Barrett bbarrett@yorku.ca
Carson Mok cmok@yorku.ca
Edward Ackad eackad@yorku.ca (Chair of the Organizing Committee)

Conference Schedule:

Time Speaker
9:45 Reception
10:00 Opening
10:15 Alireza Rafiee
10:30 Tzahi Yavin
10:45 Min Zhang
11:00 Coffee break
11:15 Victoria Martynenko
11:30 Yan Sun
Lunch Provided by PAGE
1:00 Steve Beale
1:30 Brynle Barrett
1:45 Edward Ackad
2:00 Closing

About the Lion Tamarins:

Lion tamarins have a mane derived from long hairs on the top of the head, cheeks and throat. The golden lion tamarin’s color is predominantly golden with occasional orange, brown or black coloration on the tail and forepaws. It weighs about 0.5 kg (1.1 lb) and averages about 25 cm (10″) in head/body length, not counting the tail. The golden lion tamarin prefers primary lowland tropical forest from sea level to 1000 m (3300′). Golden lion tamarins are omnivorous, feeding on fruits, gum, nectar, insects, and small vertebrates. The golden lion tamarin is diurnal and predominantly arboreal. It is usually found at heights of 3 – 10 m (10 – 30′) above the forest floor. It sleeps there at night in tangled vegetation or, more often, in a hole in a tree, such as an abandoned woodpecker nest. Most golden lion tamarins live in reproductive groups that occupy stable territories. The average number of individuals/group in one study was 5.4. In the wild, groups usually consist of one breeding adult of each sex and younger animals. Golden lion tamarins are cooperative breeders: all adult members of a group help to carry and feed the offspring of the group, with the adult male commonly doing the largest share. The mother only takes the babies to nurse them. In the 19th century, the golden lion tamarin occurred in Brazil in the coastal forests of the states of Rio de Janeiro and Espirito Santo. By the early 1980’s it was known only from remnant forests in the state of Rio de Janeiro in an area of occupied habitat probably totaling considerably less than 900 sq km (350 sq mi). The wild population is currently fragmented into 17 different subpopulations in isolated forest patches throughout its small range. More than 90% of the original Atlantic coastal forest, which contains the golden lion tamarin’s habitat, has been lost or fragmented to obtain lumber and charcoal and to clear out areas for plantations, cattle pasture, and development. Capture for zoos and private collections also contributed to its decline in the past. The golden lion tamarin is still under severe threat from continued deforestation, much of which is undertaken to create weekend beach properties. Less than 2% of the forest remains in the region where the golden lion tamarin lives.

Source: animalinfo

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The 2008 Woolly spider monkey conference Abstracts

28 March 2008conference2008 conference, abstractsJesse Rogerson

Abstracts:

Banafsheh Hashemi Pour
A new finite element formulation for 2D nonlinear problem

This paper presents a new 2D FE formulation to treat geometrically nonlinear problems. The new formulation will use nodal coordinates as basic variables to address the limitation suffered by the existing FE methods in dealing with large displacement and rotation, where they solve for nodal displacements. Thus, the errors caused by approximation in kinematic relationship and the accumulated numerical errors arising from the incremental solution procedure of existing methods can be eliminated. 2D formulation is in progress while results in 1D are available.

Xiaoyi Dong (sunne)
SHAPELETS: a new method for the galaxy imaging analysis

Galaxies are most common objects in our universe. Studying galaxies relies on spectroscopic or photometric (imaging) methods. Photometry is much less time-consuming comparing with spectroscopy method, it is ideal to study galaxies classification and variety of galaxies properties at least in statistic sense. Many multi-filter imaging surveys have been done or are being carried on (such as Sloan Digital Sky Survey and CFHT Legacy Survey). Benefits of using multi-filter imaging data are many, for example, galaxies can be classified based on colour-colour diagram. But different filters usually have different PSFs (point spread functions), which causes different imaging have different physical scales. A general method to solve the different PSFs problem is to convolve image of smaller PSFs to match the image of the widest PSF, with the sacrifice of the spatial resolution. SHAPELETS is a new imaging analysis method which is known for studying weak lensing image. We borrow this method to study nearby galaxies. The basic ideal of SHAPELETS is to decompose the image into a series basic functions, which are Gaussian function weighted Hermite polynomial and are orthonormal. The image can be reconstructed using SHAPELETS coefficients with or without a PSF. After a careful test of SHAPELETS, I conclude that SHAPELETS can reconstruct a fair good model to represent the original image, and overall meets the requirement of our work.

Steve Beale
Charge Parity Violation in Bottom Physics

The predominance of matter over antimatter in the universe is know as the baryon asymmetry. Weak processes which violate the charge-parity (CP) symmetry may help explain this phenomenon. These processes are included in the current Standard Model (SM) of particle physics, however they are not predicted to be sufficient to account for the observed asymmetry. Many new models beyond the SM include additional sources of CP violation which may account for this difference. This makes measurement of CP violating parameters an important test for physics beyond the SM.In this talk I will explain the CP symmetry, how it is broken, and how it can be measured using b-meson decays.

Jesse Rogerson
Chandra X-ray Observations of Two Unusual BAL Quasars

Reporting on the results of X-ray observations which do not detect two unusual, luminous FeLoBAL quasars. To block the X-ray emission from these quasars requires high and tightly constrained column densities. To account for the observed characteristics of the quasars requires constrained ionization parameters and density. Based on models using CLOUDY photoionization simulations, the constraints match the observations.

Vyacheslav Galymov
T2K – the next generation long baseline neutrino oscillation experiment

I will provide an overview of the phenomenon of neutrino oscillations, show recent results, and talk about future experiments (mostly T2K).

Invited Speaker: Dr. Randy Lewis
Two-bottomed baryons and exotic light mesons

In nature, all quarks are confined within composite objects. Many such objects have been observed, but some theoretical expectations remain unconfirmed by experiment. What is the status of our understanding in those cases? The vital role of computational theory (i.e. “lattice QCD”) will be discussed through two examples: one involving a pair of heavy quarks and the other with only light quarks.

Joe Borbely
Microwave Measurement of the n=2 Triplet P Fine-Structure of Helium using Ramsey Separated Oscillatory Fields

The Ramsey method of separated oscillatory fields is used to make a very precise microwave measurement of the n=2 triplet P J=1-to-J=2 interval in helium. The excellent signal-to-noise obtained in these measurements allows for extensive studies of systematic effects. The separated-oscillatory-field method allows for subnatural linewidths and provides the ability to vary the lineshape to further study systematic effects. We are in the final stages of completing themeasurement of the 2.29-GHz interval at a precision of less than 500 Hz. Comparison between precise measurements of the n=2 triplet P fine structure and theoretical predictions will allow for a precise determination of the fine-structure constant when the current large discrepancy between experiment and theory is resolved.

Alireza Rafiee
Radiation Screening Effect and Noise factor on Black Hole mass estimates

We study the sensitivity of Super-Massive Black Hole mass estimates to background noise and the quasar’s Eddington ratio. Using a sample of high signal-to-noise ratio quasar spectra from the SDSS DR3, we examine the effect of added background noise on our ability to accurately reconstruct the quasar spectra using Principal Component Analysis, PCA. We study the dispersion in the resulting BH mass estimate as the noise is increased. We also take into account the effect of the radiation screening force on the BH Virial mass estimate. We modify the previously generated scaling relationship which estimates black hole mass.

Yan Sun
Trends in structure and stability of atomic clusters

The properties of atomic cluster vary based on the element and the number of atoms it is made of. By doing a series of unbiased global search with the high-performance technology provided by SHARCNET, we study the structural trends for different groups of atomic clusters and come up with factors that govern cluster structure and stability.

Carson Mok
Measuring gravity with a single state atom interferometer

We describe a method of measuring gravity using a single state atom interferometer. Two standing wave pulses separated by T are applied to a sample of laser cooled rubidium atoms. The atoms evolve into a superposition of momentum states separated by 2hbar k, producing a density grating in the sample that dephases due to the velocity distribution of the sample. The grating that rephases at t= 2T due to the second pulse has a period of lambda/2. This grating is detected by backscattering a readout pulse into a balanced heterodyne detector. The phase of the light is measured against an optical local oscillator. The accumulation of phase as a function of T can be used to find a value for gravity. We have measured g to a precision of 10ppm on a time scale of 20ms by acquiring data over 10 minutes. We discuss improvements to the experiment via increasing time scale, vibration isolating and shielding and correction the RF phase to compensate for mirror vibrations.

Brynle Barrett
Wave Function Simulations of a Matter Wave Interferometer

We present simulations to understand a single-state atom interferometer used to measure the atomic recoil frequency with laser cooled atoms. In the experiment, a standing wave laser is pulsed on at t = 0 which creates a superposition of momentum states. At t = T, a second standing wave pulse diffracts the momentum states again so that a density grating is formed in the vicinity of t = 2T. This grating is associated with the interference of momentum states separated by 2 ħ k. A traveling wave read-out pulse is applied to the sample at this time and the backscattered light from the grating is detected as the echo signal. The amplitude of the echo signal is periodic at the atomic recoil frequency and the duration of the echo envelope is related to the velocity distribution in the sample. Our goal is to model several aspects of the echosignal, both in the short pulse (Raman-Nath) and long pulse (Bragg) regimes, such as the dependence of the echo amplitude on the Rabi frequency, pulse length and spontaneous emission.

Invited Speaker: Dr. Tzahi Yavin
How Strong is the Strong Nuclear Force? In this presentation

I will discuss the strong nuclear force that binds quarks into nucleons and hadrons as described by the theory of quantum chromodynamics (QCD), and how its strength can be determined quite accurately from the decays of the tau lepton into hadrons.

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Physics and Astronomy Graduate Executive

York University

All posts by Jesse Rogerson

The 2007 Golden lion tamarin conference Abstracts

The 2007 Golden lion tamarin conference

The 2008 Woolly spider monkey conference Abstracts