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  • richardmitnick 3:56 pm on September 15, 2014 Permalink | Reply
    Tags: , , TRIUMF   

    From Triumf: “Postdoc Publishes Theory Breakthrough” 


    Triumf Lab

    15 September 2014
    Nick Leach, Outreach Assistant

    The basic interaction between the constituents of an atomic nucleus (‘nucleons‘ means neutrons or protons) has been well understood for decades; however, the interaction’s strength has meant that calculations for all but the very simplest nuclear systems (e.g. the deuteron = 1 proton + 1 neutron) were initially too complex to do from basic principles, necessitating various approximation methods to make reliable predictions. Nonetheless, theoretical groups worldwide have persevered in their attempts at establishing reliable “ab initio” techniques, and much progress has been made in describing ever-larger nuclei starting from the fundamental nucleon forces. TRIUMF theorists have been at the forefront of many of these advances.

    neu
    The quark structure of the neutron. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.

    pro
    The quark structure of the proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.

    Recently, scientists from TRIUMF and the Lawrence Livermore National Laboratory (LLNL) published a paper in the prestigious Physical Review Letters outlining a technique which for the first time enables researchers to analyze systems of three nuclear clusters in relative motion while treating the individual nucleons as fundamental components interacting by accurate nucleon-nucleon interactions. The work by the Theory postdoc Carolina Romero-Redondo and Petr Navratil (Theory Department, TRIUMF) in conjunction with Sofia Quaglioni and Guillaume Hupin (LLNL) has produced the first successful ab initio analysis describing energy states in the He-6 nucleus (2 protons + 4 neutrons).

    chart

    cr
    Carolina Romero-Redondo

    He-6 is an exotic nucleus that can be described as a three-cluster “halo” nucleus – a tightly bound He-4 core orbited by two neutrons. Part of what makes this particular nucleus so fascinating is that though the trio are bound together when all three bodies are present, removing just one renders the whole structure unstable. These are known as “Borromean” nuclei, after the similarly named Borromean rings, which exhibit a similar all-or-nothing structure. The He-6 nucleus is difficult to study experimentally and as such its energy spectrum is not yet firmly established. Excitingly, the results by Romero-Redondo, et al. are consistent with recent experiments, correctly identifying some known energy states (‘resonances’). They also predict new energy states and do not find others (e.g. low-energy “1-“ state) predicted by other formalisms.

    In the future, this new approach will be applied to study systems such as H-5 as a 3H+n+n trio, and Li-11 as a 9Li+n+n configuration.

    Having completed her term at TRIUMF, Carolina will continue her innovative research on three-cluster systems at her new appointment at LLNL.

    Congratulations to Romero-Redondo and her colleagues for this excellent contribution!

    See the full article here.

    World Class Science at Triumf Lab, British Columbia, Canada
    Canada’s national laboratory for particle and nuclear physics
    Member Universities:
    University of Alberta, University of British Columbia, Carleton University, University of Guelph, University of Manitoba, Université de Montréal, Simon Fraser University,
    Queen’s University, University of Toronto, University of Victoria, York University. Not too shabby, eh?

    Associate Members:
    University of Calgary, McMaster University, University of Northern British Columbia, University of Regina, Saint Mary’s University, University of Winnipeg, How bad is that !!
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  • richardmitnick 4:08 pm on January 21, 2012 Permalink | Reply
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    From Quantum Diaries: Byron Jennings “The Interpretation of Quantum Mechanics” 

    Byron Jennings is simply amazing. You can follow his blog here. Looks like one needs to go backwards, through his archive, one post at a time; but it is worth it. I doubt that there are many scientists who can write with the articulate elegance of Bryan Jennings. Here is the introduction to his latest post.

    bj
    Byron Jennings

    January 20th, 2012

    “When I first started dabbling in the dark side and told people I was working on the philosophy of science, the most common response from my colleagues was: Oh the foundations of quantum mechanics? Actually not. For the most part, I find the foundations of quantum mechanics rather boring. Perhaps that is because my view of science has a strong instrumentalist tinge, but the foundations of quantum mechanics have always seemed to me to be trying to fit a quantum reality into a classical framework; the proverbial triangular peg in an hexagonal hole. Take wave-particle duality for example. Wave and particles are classical idealizations. The classical point particle does not exist, even within the context of classical mechanics. It should come as no surprise that when the classical framework breaks down, the concepts from classical mechanics are no longer valid. What quantum mechanics is telling us is only that the classical concepts of waves and particles are no longer valid. Interesting, but nothing to get excited about.”

    And, here is Byron’s concluding of this subject.

    So what is the interpretation of quantum mechanics? An important part seems to be that wave functions are the information the observer has on the quantum system, and is not a property of the quantum system alone. If you do not like that, well there is always instrumentalism, i.e. shut up and calculate.

    See the full post here.

    Participants in Quantum Diaries:

    Fermilab

    Triumf

    US/LHC Blog


    CERN

    Brookhaven Lab

    KEK

     
  • richardmitnick 4:31 pm on December 17, 2011 Permalink | Reply
    Tags: , , , TRIUMF   

    From Byron Jennings, TRIUMF via Quantum Diaries: “Can Science Answer the ‘Why’ Question?” 

    Byron Jennings is one of the finest and most thoughtful writers we have.

    i1
    Byron Jennings

    “The development of science is often portrayed as a conflict between science and religion, between the natural and the supernatural. But it was equally, if not more so, a conflict with Aristotelian concepts: a change from Aristotle’s emphasis on why to a dominant role for how. To become the mainstream, science had to overcome resistance, first and foremost, from the academic establishment and only secondarily from the church. The former, represented by the disciples of Aristotle and the scholastic tradition, was at least as vociferous in condemning Galileo as the latter. Galileo, starting from when he was a student and for most of his career, was in conflict with the natural philosophers. (I decline to call them scientists.) His conflict with the church was mostly towards the end of his career, after he was fifty and more seriously when he was nearing seventy. The church itself even relied on the opinions of the natural philosophers to justify condemning the idea the earth moved. In the end science and Galileo’s successors won out and Aristotle’s natural philosophy was vanquished: the stationary earth, the perfect heavens (circular planetary orbits and perfectly spherical planets), nature abhorring a vacuum, the prime mover and so on. For most of these it is so long and good riddance. So why do philosophers still spend so much time studying Aristotle? I really don’t know.”

    See Byron’s full post here.

    Participants in Quantum Diaries:

    Fermilab

    Triumf

    US/LHC Blog


    CERN

    Brookhaven Lab

    KEK

     
  • richardmitnick 12:47 pm on December 3, 2011 Permalink | Reply
    Tags: , , , , TRIUMF   

    From Byron Jenning of Triumf at Quantum Diaries: “The Trouble with Particle Physics” 

    bj

    “What is the current trouble with particle physics? That’s an easy one: a paucity of new experimental results that challenge the status quo. In contrast, in the past twenty years, cosmology has surged ahead, fueled by the new results from COBE, WMAP, Hubble, and other novel devices. Yet that field may now also be reaching the point of diminishing returns. Without new experimental results any field stagnates. But before addressing this in more detail let’s look at some other suggested problems with particle physics.” Which Byron does quite well.

    See the full post here.

    Participants in Quantum Diaries:

    Fermilab

    Triumf

    US/LHC Blog


    CERN

    Brookhaven Lab

    KEK

     
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