• "live post" from the Texas Symposium on Relativistic Astrophysics

    From Phillip Helbig (undress to reply)@21:1/5 to All on Mon Dec 16 21:47:31 2019
    A few weeks ago, fellow moderator Jonathan suggested that I "live-post"
    from a conference, so I'll do so this week. He was actually thinking
    about another conference next year (not sure if I shall go), but I might
    as well do so from this year's Texas Symposium on Relativistic
    Astrophysics in Portsmouth, England. It won't actually be live.
    Rather, each evening, if I have time, I can mention some things which I
    found interesting. The internet connection is slow, so I'll keep things simple, though there should be enough to go on if someone wants to
    learn more.

    In his opening welcome, LOC president David Wands mentioned the late,
    great Wolfgang Rindler. Born in 1924, he died earlier this year.
    Fleeing from Nazi Austria as a child, he went to university in England
    and taught there for a bit before moving to Cornell University in the
    USA in the mid-1950s, then in 1963 to what would later become the
    University of Texas at Dallas, where he stayed the rest of his life. He
    was known for many things: the definitive paper on cosmological horizons (coining the term "event horizon"), a famous textbook on relativity,
    Rindler coordinates (not many people have their own coordinates). He
    was at the first Texas Symposium in 1963, and helped organize the 50th-anniversary one in 2013. Although I had seen him at conferences
    before and we had exchanged a few emails, I was happy to finally meet
    him in 2013, where he proved to be a really nice guy as well.

    Chris Reynolds, the current Plumian Professor of Astronomy in Cambridge, mentiond that axions, or axion-like particles, small-mass particles
    often touted as dark-matter candidates, could, due to their small mass
    and hence macroscopic de Broglie wavelength, form gravitational
    analogs of atoms, with black holes as nuclei. This can lead to energy transmission from the black hole, and the fact that spinning black holes
    are observed puts constraints on the number and properties of such

    Enrique Gaztanaga gave an interesting talk based on the idea that
    causality can determine the value of the cosmological constant, though
    based on the assumption that Lambda alone is unphysical. The details
    are a bit complicated, but for an infinite universe he expects a Lambda
    of zero and for a finite one a value similar to that which is observed,
    which might also explain some of the "anomalies" in the CMB. See arXiv:1911.13199.

    Going with the times, the conference has its own app. As at all Texas Symposia, there are plenary sessions in the mornings and about 10
    parallel sessions in the afternoons. A particularly useful feature
    allows one to come up with a custom schedule by choosing talks one wants
    to hear from various sessions. The participant list includes pictures
    if the participants chose to upload them, one can send messages to other participants, request meetings, and so on (useful where there are
    several hundred participants and talks in several different buildings).

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