Re: Neutron Stars Without Gravity
- From: glhansen@xxxxxxxxxxxxxxxxxxxxx (Gregory L. Hansen)
- Date: Thu, 19 May 2005 20:45:15 +0000 (UTC)
In article <1116430203.a07de49f85ec1aa9dc7fc19b98ced0cf@teranews>,
Jan Panteltje <pNaonStpealmtje@xxxxxxxxx> wrote:
>On a sunny day (Wed, 18 May 2005 14:39:51 +0000 (UTC)) it happened
>glhansen@xxxxxxxxxxxxxxxxxxxxx (Gregory L. Hansen) wrote in
><d6fk3n$mt5$1@xxxxxxxxxxxxxxxxxxxxxxxx>:
>
>>
>>There's a talk here today by Ignatovich, "Neutron Stars Without Gravity".
>>The abstract posted on the wall reads:
>>
>>"The optical potential used routinely for the description of neutron
>>interactions with condensed matter, in particular, in reflectometry, is a
>>long range interaction created by short range strong interaction. This
>>optical potential depends on density N and scattering amplitude b. For
>>negative b it is attractive and for large N becomes high. Neutrons stars
>>can be considered as neutrons trapped by their own optical potential,
>>which can be even greater than the gravitational one. Some interesting
>>features of this approach are discussed and comparison with a common
>>approach is made."
>>
>>I'm heading out for it.
>PLZ let us know what it says!
Dr. Ignatovich talked about just what the abstract suggested. His
PowerPoint had lots of formulas and few words, he didn't speak very
loudly, my attention wandered, and I got there a few minutes late because
I was fiddling with the plate reader in the basement. But anyway, he
argued that below a critical radius of around 20 km the neutron optical
potential becomes stronger than the gravitational potential, so you would
still have a neutron star even if gravity was turned off. And he said it
would continue to contract, and calculated a pressure which I presume gave
an eventual limiting case although I wan't rightly conscious through it.
And there's a point where the optical potential would overcome an outward
pressure, and the start would contract and explode. His thesis was that
the optical potential is an important aspect of stellar evolution, even in
normal stars, but it hasn't been considered.
That begged a question of what the lower limit would be. In his scenario,
gravity compressed the material until the optical potential alone could
hold it. But clearly there's a lower limit since there is no bound
neutron-neutron state, and atoms with too many neutrons tend to decay or
fission. Somewhere in between I'd think there's an Earth mass or a
baseball or something that represents a limiting case that would form a
stable neutron glob if it was somehow compressed enough. But he didn't
seem to understand the question, and I didn't really get an answer.
His thesis was received with some skepticism, and particularly loud
skepticism by the other Russian present. The optical potential is a
smoothing out, an approximation, of the nuclear potential and, well,
there is no bound neutron-neutron state. I was a little taken aback
myself at one point when Ignatovich derived a condition where the optical
potential was stronger than the nuclear potential. Hmm... I didn't
follow the theoretical development well enough to say what, if anything,
he did wrong, but I can't really enthusiastically endorse his thesis at
this point.
--
"The preferred method of entering a building is to use a tank main gun
round, direct fire artillery round, or TOW, Dragon, or Hellfire missile to
clear the first room." -- THE RANGER HANDBOOK U.S. Army, 1992
.
- References:
- Neutron Stars Without Gravity
- From: Gregory L. Hansen
- Re: Neutron Stars Without Gravity
- From: Jan Panteltje
- Neutron Stars Without Gravity
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