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NSBP and SAIP Members on LHC Lead-Lead Collisions November 16, 2010

Posted by ASTRO Section Chair in : Astronomy and Astrophysics (ASTRO), Cosmology, Gravitation, and Relativity (CGR), Mathematical and Computational Physics (MCP) , 2comments

LHC Achieves Heavy Ion Collisions
On Sunday November 7 at 1 am local time the first heavy ion collisions were observed in the Large Hadron Collider (LHC) near Geneva, Switzerland.  By the following Monday morning the heavy ion beam was stably producing a steady stream of collisions such that the physics analysis could start in earnest.  By the end of the week a sufficient number of events had been observed to reach the first conclusions.

Witnessing this historic event was Dr. Zinhle Buthelezi from South Africa’s iThemba LABS who was on duty in the control room of the ALICE (A Large Ion Collider Experiment) detector at the time of the first collisions.  Other members of the iThemba LABS team, Deon Steyn, Siegie Foertsch, and Zeblon Vilakazi, as well as the team from the University of Cape Town led by Jean Cleymans have also been participating in the ALICE experiment.  More

ALICE, Quark-Gluon Plasmas and the Origin of the Universe
The goal of ALICE is to observe the so-called Quark Gluon Plasma (QGP).  This plasma is partially analogous to the more well-known electronic plasma that results when a gas is so hot that its electrons are liberated from their atomic nuclei.  Like electrons are constituents of atoms, quarks and gluons are constituents of nucleons – protons and neutrons.  They can likewise be “deconfined” from nucleons at high energy densities like those that existed at the very moment of the Big Bang, or can be reproduced in high energy accelerators like the Relativistic Heavy Ion Collider (RHIC) or the LHC.  Thus the results gained from ALICE and RHIC give insights into the state of energy and matter in the first microseconds of the universe, before condensation into neutrons, protons, and subsequently atoms.   More

NSBP Members Clifford Johnson and Stephon Alexander on the ALICE collisions
Experimental Excitement
ALICE – A Cosmologist’s Point of View

Theoretical physicists have studied QGPs using a variety of techniques.  Perhaps the most successful method is due to Dr. Juan Maldacena, a plenary speaker at the 2005 Joint Annual Conference of the National Society of Black Physicists and the National Society of Hispanic Physicists.  The so-called “AdS/CFT correspondence” relates string theory to gauge theories like quantum chromodynamics (QCD) which describes the interactions between quarks and gluons. Professor Jim Gates has commented, “So, the next time someone tells you that string theory is not testable, remind them of the AdS/CFT connection…”  Since then experimental, observational, and theoretical evidence has expanded from particle theory to condensed matter physics.

South African Participation at CERN
In addition to the ALICE experiment, South African physicists are participates in the ATLAS experiment.  Dr. Simon Connell, President-elect of the South African Institute of Physics leads the ATLAS Team at the University of Johannesburg.  “ATLAS is designed to answer some of the most fundamental questions about the nature of the universe, like how and why particles have mass,” he explains.

This past summer South Africa hosted the first biennial African school on fundamental subatomic physics and its applications. More

2010 African Physics School

Courtesy of Brookhaven National Lab

South African participation in particle physics brings many benefits to the country and continent, most notably in information and computing technology (ICT).  SANReN, the grid computing network that allows physicists in South Africa to receive results from the LHC is used by many others in science and business, and this network will by design be extended to everyday consumers and learners.  More

ALICE, Quark-Gluon Plasmas and the Origin of the Universe – A Cosmologist’s Comment November 16, 2010

Posted by ASTRO Section Chair in : Astronomy and Astrophysics (ASTRO), Cosmology, Gravitation, and Relativity (CGR) , 1 comment so far

Currently the best modern framework for understanding the origin of large scale structure in our universe is called cosmic inflation.

While still not completely resolved, inflation predicts the observed features of the universe split seconds after the big bang and three hundred thousand years during another era where the universe was filled with another type of plasma-an ionized gas of baryons and photons.   However when inflation was first ignited (10-36 seconds), the universe was thought to be filled with pure vacuum energy, no particles and radiation.

One of the big mysteries in cosmology and fundamental physics is to understand precisely how inflation ended and dumped its energy into the form of radiation.  A curious hint is that at time 10-12 seconds the universe was filled only with the quark-gluon plasma.

A key mystery of cosmology and fundamental physics is to understand how the universe went from the inflating state to the quark-gluon plasma state.  By understanding this new state of matter, the quark gluon plasma, physicists can help us understand the physics of the early universe right at the LHC.

Likewise, string theorists are developing new tools within the framework of M/String-Theory called the Ads/CFT correspondence which gives new insights into the non-perturbative physics by relating the physics of charged black holes “holographically” to the quark-gluon plasma.  It is amusing to speculate on how this new understanding could impact the experiments at the LHC and any possible relation to the physics of cosmic inflation.

Stephon Alexander

News From The Front, VII: What is Fundamental, Anyway? July 4, 2009

Posted by CGR Section Chair in : Cosmology, Gravitation, and Relativity (CGR), Nuclear and Particle Physics (NPP) , add a comment

Editor’s note: The following excerpt comes to us from theoretical physicist Clifford Johnson, a professor in the University of Southern California Department of Physics and Astronomy. Professor Johnson’s work primarily focuses on (super)string theory, gravity, gauge theory and M-theory. — CPW

One of the words I dislike most in my field – or more accurately, a common usage thereof – is “fundamental”. This is because it is usually used as a weapon, very often by people in my area of physics (largely concerned with particle physics, high energy physics, origins questions and so forth), to dismiss the work of others as somehow uninteresting or irrelevant. I don’t like this. Never have. Not only is it often allied to a great deal of arrogance and misplaced swagger, it is often just plain short-sighted, since you never know where good ideas and techniques will come from. A glance at the history of physics shows just how much cross-pollination there is between fields in terms of ideas and techniques. You never know for sure where valuable insights into certain kinds of problems may come from.

Fundamental physics is a term I used to hear used a lot to refer to particle physics (also called high energy physics a lot more these days). This was especially true some years back when I was an undergraduate in the UK, and it persisted in graduate school too, and is still in use today, although I think it is declining a bit in favour of less loaded terms. Somehow, a lot of particle physics is regarded as being all about the “what is everything made of at the very smallest scales” sort of question, first discussing atoms, and then atoms being made of electrons surrounding a nucleus, and the nucleus being made of protons and neutrons, and those in turn being made of quarks, and so on, in this was arriving at a list of “fundamental” particles. There’s the parallel discussion about the “fundamental” forces (e.g., electromagnetism and the nuclear forces) being described in terms of exchanges of particles like photons, gluons, and W and Z particles and so forth. There’s no real harm in the use of the term fundamental in this context, but this is about where the word gets elevated beyond its usefulness and starts becoming a hurdle to progress, and then a barrier. Somehow, “fundamental”, meaning “building block” gets turned, oddly, into “most important”. The issue of what the smallest building blocks are gets elevated to the most important quest, when it is in reality only a component of the story. It is rather like saying that the most important things about the Taj Mahal are the beautiful stones, tiles, and other components from which it is constructed.

Perspectives have evolved a bit since my salad days, with the rise of wider recognition of the connection between particle physics, and astrophysics and cosmology. I think that things are (these days) more widely seen to be the more rich interconnected and beautiful landscape of phenomena that they are, but I still find, especially among younger people, the “building block” attitude to be prevalent.

I raise this since sometimes I find that people don’t understand that there are fundamental and vital questions in other areas that connect to so many interesting areas of physics. […]

Read the rest of the article on Asymptotia here.