Black hole spins?

Jim1348
Jim1348
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Topic 218703

Could black hole spins (or the accretion disk thereof) be detected by Einstein?

Mike Hewson
Mike Hewson
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Short answer : No. Longer

Short answer : No.

Longer answer : E@H is all setup to catch persistent GWs from non-axisymmetric mass arrangements. A black hole may be non-axisymmetric, but not for long. It will quickly radiate away until symmetric. So no persistent signal. Accretion disks behave likewise, and wouldn't be dense enough anyway. You want neutron star density or better.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Jim1348
Jim1348
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Very well.  I just hope that

Very well.  I just hope that if they do not pick up any neutron stars, they can use their advanced signal processing capability for something else. 

It would be nice to get a status update too.  I am not sure where we are with the runs.  It seems that we should be seeing some results from the last one, whatever that is.

Thanks.

Mike Hewson
Mike Hewson
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Overall the project has

Overall the project has discovered some 50 odd new pulsars from electromagnetic data ( radio/gamma ).

If you can tease out the detail within the server status page, it is useful to glance at.

{ For instance under the heading "GPU productivity ( last 7 days )" you'll discover that : despite NVIDIA hosts outnumbering ATI/AMD at about 2 to 1, the NVIDIA hosts still don't quite exceed the ATI/AMD on daily credit earned .... :-))) }

If you are referring to science results/conclusions/publications then there are notices ( with links ) from time to time on the news page eg. https://arxiv.org/abs/1903.09119 most recently.

Cheers, Mike.

( edit ) Oh, a work generator daemon "not running" may still mean work is being done, it's just that generally the project can create work units quicker than the hosts can return results to validate. So that daemon will only operate part of the time.

( edit ) You may be thinking that we haven't yet achieved anything GW-wise as no continuous wave signal is yet discovered. But we have ! We have found out how 'quiet' these waves must be if they exist. In turn that tells theorists something about neutron stars, especially it's material properties or 'equation of state' ( roughly meaning how does the pressure of some volume of star material varies with density ). Maybe gravitational attraction ( density dependent ) overwhelms pressure such that non-axisymmetric neutron stars don't persist as such ie. 'mountains' on neutron stars get flattened or won't form. It is known that pulsars have timing glitches which may be evidence for re-arrangement of mass, sort of a star quake. In any event our published results have placed bounds on what the equation of state must be, in turn that can inform upon, say, the maximum possible mass of a neutron star before it forms an event horizon and becomes a black hole. Put another way, how much repulsion can quarks provide before gravity wins .....

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

rbpeake
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Jim1348
Jim1348
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Thanks for both responses. 

Thanks for both responses.  Negative results can be as important as positive results.  But it appears that pulsars can provide similar information.  And any reference to the BOINC contribution is remarkably subtle. 

This places it in context.

 

PS - I was reminded by a friend that it is ANZAC day. 

Gary Roberts
Gary Roberts
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Jim1348 wrote:It would be

Jim1348 wrote:
It would be nice to get a status update too.  I am not sure where we are with the runs.  It seems that we should be seeing some results from the last one, whatever that is.

Have you had a look under the "Science" tab?  There are a further 8 sub-menu items, some of which contain quite a lot of information as to progress and results.  For example, there is a large list of links to papers and reports under the "Publications" item, going right back to 2005 - the first year of this project existing.  Volunteers even then were interested in progress and Bruce was kind enough to provide a progress report in the latter half of that first year.

The 'golden' period of pulsar discoveries was between 2010 and 2015.  There are some 8 papers covering those - initially radio pulsars and then gamma-ray pulsars when the Fermi satellite data became available.  The Fermi data keeps on improving and we are likely to keep finding new objects as a result.

During all that time LIGO has been upgraded and made a lot more sensitive so the chance of finding the 'continuous' type of GW emissions is getting better all the time.  It surely is only a matter of time before a continuous emission is finally detected..

If you saw Bernd's brief mention of an injection run recently, you could easily speculate about what that might mean.  To me, it means they probably intend to inject simulated emissions into the data, perhaps to improve the algorithms with a view to being able to detect progressively weaker signals.  In other words, to quantify the current level of detectability and perhaps lower it.  To me, that seems to suggest they think they are getting very close to making a detection.

It's an exciting time to be involved in this project.

 

Cheers,
Gary.

Jim1348
Jim1348
Joined: 19 Jan 06
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Credit: 177,070,724
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Gary Roberts wrote:During all

Gary Roberts wrote:
During all that time LIGO has been upgraded and made a lot more sensitive so the chance of finding the 'continuous' type of GW emissions is getting better all the time.  It surely is only a matter of time before a continuous emission is finally detected..

Yes, that is the type of thing I am looking for.  I will keep track of it in the Science tab.  Thanks.

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