Science questions

Ben Owen
Ben Owen
Joined: 21 Dec 04
Posts: 117
Credit: 33,818,647
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Topic 189192

Hi folks,

One of the reasons I've been laying low for a little while is to help the APS (American Physical Society) with the APS Einstein@Home web site.

It's not just project participants who are asking questions about general relativity, gravitational waves, pulsars, and related topics. There's a lot of traffic over this "World Year of Physics" in honor of the 100th anniversary of Einstein's best year. So Jennifer Fischer of the APS suggested setting up a regular Q&A as well as some background information. It might be more accessible than just posts that drop towards the bottom of the screen after a while. It's also supposed to be accessible in the sense that the answers are geared toward a broader (less technical) public than just hardcore crunchers.

I'm still reading these boards and answering some questions. But if you ask a science question of broad interest, I might ask you if we can port it over there.

Ask away,
Ben

hoarfrost
hoarfrost
Joined: 9 Feb 05
Posts: 203
Credit: 48,051,828
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Science questions

Can my Einstein@Home client found a gravitational waves from colliding neutron stars or black holes? Or it may detect GW only from "unvisible" pulsars?

Thank you!

gravywavy
gravywavy
Joined: 22 Jan 05
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Can my Einstein@Home client

Message 11721 in response to message 11720


Can my Einstein@Home client found a gravitational waves from colliding neutron stars or black holes?

At present the software is looking for continuous sine waves in the data: these are expected from rotating bodies rather than collisions.

The E@H setup could presumably also look for collisions but would need a different piece of software to be downloaded. I have not heard of any plans to write that software

Or it may detect GW only from "unvisible" pulsars?

if it is visible it will also pulsate at the same frequency as the GW: both effects are tied to the speed of rotation, at least if I understand the scientific postings correctly. I assume this means we can see GW from a massive rotating object whether it is visible or not.

~~gravywavy

Ben Owen
Ben Owen
Joined: 21 Dec 04
Posts: 117
Credit: 33,818,647
RAC: 15,584

Hoarfrost, Can my

Message 11722 in response to message 11720

Hoarfrost,

Can my Einstein@Home client found a gravitational waves from colliding neutron stars or black holes? Or it may detect GW only from "unvisible" pulsars?

The answer to your question overlaps with this one.
Basically, the answers to your questions are "no" and "yes".

Searches for different sources involve playing different mathematical tricks with the data. Most of them (certainly for collisions and pulsars) are based on matched filtering, and Fourier transforms or something similar to them usually pop up as well. Matched filtering is a very targeted method: When you're looking for colliding (we say inspiraling or merging) neutron stars or black holes in binaries, you're not looking for pulsars. And when you're looking for isolated pulsars you're not looking for pulsars in binaries.

As I said in the other answer, the decision to go for unknown or invisible pulsars was based on where the greatest need for computational power was. I didn't mention the collisions or mergers, but basically they're pretty short-lived signals (on the order of a minute) so the search for them does not consume as many CPU cycles and can be done on clusters of computers at universities. Since pulsar signals are always "on" they are much more CPU intensive to look for.

Actually, some of the planned searches for merging neutron stars and/or black holes are starting to shoot up in cost to where it might be worth putting Einstein@Home to work on them. (Basically spins lead to a much greater parameter space to search, and in the future there will be much more data.) But if that happens it's a while down the road. Einstein@Home will be sticking with pulsars for the near future.

Hope this helps,
Ben

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