This combination is the 'state of the art' in terms of sensitivity.
Hi Bruce,
Thanks for contributing to this thread.
Given your statement above, are you prepared to speculate a little on the odds that something will be found in S5 data? In a way I guess it's probably just as important if nothing is found because I imagine that would instigate a fairly dramatic rethink about the whole deal.
Will the plans for future experiments change in any particular way depending on a positive or negative outcome for S5?
This combination is the 'state of the art' in terms of sensitivity.
Hi Bruce,
Thanks for contributing to this thread.
Given your statement above, are you prepared to speculate a little on the odds that something will be found in S5 data? In a way I guess it's probably just as important if nothing is found because I imagine that would instigate a fairly dramatic rethink about the whole deal.
Will the plans for future experiments change in any particular way depending on a positive or negative outcome for S5?
My two cents on this (actually I'm not a physicist):
If nothing is found by the Einstein@home analysis runs S5R1-S5R3 this would mean that something isn't as we expected or hoped. We would try to find out what it is and change the search depending on it, maybe just finding that what we thought wasn't the problem. Assumptions and thus reasons for not finding something include:
- the program is reasonably free of serious programming errors
- algorithm: e.g. the application of the Hough transform to "demodulated" ("F-statistic") data has never been actually tested or validated before.
- parameters: It might be that e.g. the frequency of continuous gravitational wave sources is a factor off from what we expect, in which case these gravitational waves could lie outside the spectrum where our earth-based detectors are sensitive.
- modeling: The algorithms used in Einstein@home are bound to very specific waveforms. It could even be that no sources that emit such gravitational waves exist at all.
Our current thinking is that the sensitivity of our search is not good enough for the sources we expect to detect (i.e. they exist but are too far away), so what we do is to increase the sensitivity of the detectors (which is currently done by upgrading them to "Advanced LIGO" and "VIRGO+") and data analysis (which we do by using the "hierarchical search" method).
Actually is as impossible to prove the non-existence of gravitational waves by this experiment as it is to prove the absence of bugs in a computer program just by testing it.
BTW, when will the second step in the hierarchical search (looking harder at spots in "parameter space" that seem to be interesting according to first stage results) begin? Theoretically, it could already begin for frequency bands where all workunits were already returned?
This combination is the 'state of the art' in terms of sensitivity.
Hi Bruce,
Thanks for contributing to this thread.
Given your statement above, are you prepared to speculate a little on the odds that something will be found in S5 data? In a way I guess it's probably just as important if nothing is found because I imagine that would instigate a fairly dramatic rethink about the whole deal.
Will the plans for future experiments change in any particular way depending on a positive or negative outcome for S5?
Sometime in the last year a poster prepared for a conference on S5 was linked to on the board. One of the graphs on it showed expected signal strength of known pulsars and achieved sensitivity during s5. All of the pulsars were on the wrong side of the detection threshold. :(
This combination is the 'state of the art' in terms of sensitivity.
Hi Bruce,
Thanks for contributing to this thread.
Given your statement above, are you prepared to speculate a little on the odds that something will be found in S5 data? In a way I guess it's probably just as important if nothing is found because I imagine that would instigate a fairly dramatic rethink about the whole deal.
Will the plans for future experiments change in any particular way depending on a positive or negative outcome for S5?
Sometime in the last year a poster prepared for a conference on S5 was linked to on the board. One of the graphs on it showed expected signal strength of known pulsars and achieved sensitivity during s5. All of the pulsars were on the wrong side of the detection threshold. :(
That's why Einstein@Home is looking for UNKNOWN sources. It's very likely that there are a lot of rapidly spinning neutron stars that might emit gravitational waves but not be visible electromagnetically (as pulsars).
BTW, when will the second step in the hierarchical search (looking harder at spots in "parameter space" that seem to be interesting according to first stage results) begin? Theoretically, it could already begin for frequency bands where all workunits were already returned?
CU
Bikeman
This work is underway. It is being led by Maria Alessandra Papa, one of the inventors of the hierarchical search method.
That's why Einstein@Home is looking for UNKNOWN sources. It's very likely that there are a lot of rapidly spinning neutron stars that might emit gravitational waves but not be visible electromagnetically (as pulsars).
That'd likely be the majority of neutron stars are EM invisible then? Given that we at Earth have to be hit by the beams, and repeatedly so, for a 'pulsar' label to be earned, and those beams generally sweep a lesser fraction of a full sphere's worth of solid angle? Ah, but some binary systems cause wobbles/precessions thus upping the detection chances.
Hmmm ... so if you map known EM sources with GW's, one can thus 'calibrate' their corresponding EM/GW characteristics - there'd be deeper common dependencies like moments of inertia and whatnot - so when we find many more similiar GW's without a visible EM signal we can back track. Perhaps a long bow draw, but I feel a 'standard candle' coming on. Rubbish? :-)
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Ah, but some binary systems cause wobbles/precessions thus upping the detection chances.
OTOH, when taking precession and binary systems into account, the parameter search space gets more complicated, compared to what E@H is now looking for, I guess (target waveform at the source is a fairly simple sinus wave but with a slowly decaying (maybe also increasing) frequency, but is frequency and amplitude modulated at the detectors by the earth's movement around the sun and its rotation around its spin axis). Also the frequency of GW caused by presession and the movement of binary pulsars around their center of gravity are (I guess) not inside the favorable spectrum of ground based detectors (perhaps this is LISA territory).
Ah, but some binary systems cause wobbles/precessions thus upping the detection chances.
OTOH, when taking precession and binary systems into account, the parameter search space gets more complicated, compared to what E@H is now looking for, I guess (target waveform at the source is a fairly simple sinus wave but with a slowly decaying (maybe also increasing) frequency, but is frequency and amplitude modulated at the detectors by the earth's movement around the sun and its rotation around its spin axis). Also the frequency of GW caused by presession and the movement of binary pulsars around their center of gravity are (I guess) not inside the favorable spectrum of ground based detectors (perhaps this is LISA territory).
??
CU
Bikeman
Sorry, I was referring to upping their EM detection chances by flashing at us at least semi-regularly. We don't get "beamed" by GW's in that way. Quite right, as the GW frequency is of the order of twice whatever oscillation/modulation is occurring, and for precession that is likely to be ~ lowest frequency about in a binary system, then yes that's not the LIGO band.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: This combination is the
)
Hi Bruce,
Thanks for contributing to this thread.
Given your statement above, are you prepared to speculate a little on the odds that something will be found in S5 data? In a way I guess it's probably just as important if nothing is found because I imagine that would instigate a fairly dramatic rethink about the whole deal.
Will the plans for future experiments change in any particular way depending on a positive or negative outcome for S5?
Cheers,
Gary.
RE: RE: This combination
)
My two cents on this (actually I'm not a physicist):
If nothing is found by the Einstein@home analysis runs S5R1-S5R3 this would mean that something isn't as we expected or hoped. We would try to find out what it is and change the search depending on it, maybe just finding that what we thought wasn't the problem. Assumptions and thus reasons for not finding something include:
- the program is reasonably free of serious programming errors
- algorithm: e.g. the application of the Hough transform to "demodulated" ("F-statistic") data has never been actually tested or validated before.
- parameters: It might be that e.g. the frequency of continuous gravitational wave sources is a factor off from what we expect, in which case these gravitational waves could lie outside the spectrum where our earth-based detectors are sensitive.
- modeling: The algorithms used in Einstein@home are bound to very specific waveforms. It could even be that no sources that emit such gravitational waves exist at all.
Our current thinking is that the sensitivity of our search is not good enough for the sources we expect to detect (i.e. they exist but are too far away), so what we do is to increase the sensitivity of the detectors (which is currently done by upgrading them to "Advanced LIGO" and "VIRGO+") and data analysis (which we do by using the "hierarchical search" method).
Actually is as impossible to prove the non-existence of gravitational waves by this experiment as it is to prove the absence of bugs in a computer program just by testing it.
BM
BM
BTW, when will the second
)
BTW, when will the second step in the hierarchical search (looking harder at spots in "parameter space" that seem to be interesting according to first stage results) begin? Theoretically, it could already begin for frequency bands where all workunits were already returned?
CU
Bikeman
RE: RE: This combination
)
Sometime in the last year a poster prepared for a conference on S5 was linked to on the board. One of the graphs on it showed expected signal strength of known pulsars and achieved sensitivity during s5. All of the pulsars were on the wrong side of the detection threshold. :(
RE: RE: RE: This
)
That's why Einstein@Home is looking for UNKNOWN sources. It's very likely that there are a lot of rapidly spinning neutron stars that might emit gravitational waves but not be visible electromagnetically (as pulsars).
Bruce
Director, Einstein@Home
RE: BTW, when will the
)
This work is underway. It is being led by Maria Alessandra Papa, one of the inventors of the hierarchical search method.
Cheers,
Bruce
Director, Einstein@Home
RE: That's why
)
That'd likely be the majority of neutron stars are EM invisible then? Given that we at Earth have to be hit by the beams, and repeatedly so, for a 'pulsar' label to be earned, and those beams generally sweep a lesser fraction of a full sphere's worth of solid angle? Ah, but some binary systems cause wobbles/precessions thus upping the detection chances.
Hmmm ... so if you map known EM sources with GW's, one can thus 'calibrate' their corresponding EM/GW characteristics - there'd be deeper common dependencies like moments of inertia and whatnot - so when we find many more similiar GW's without a visible EM signal we can back track. Perhaps a long bow draw, but I feel a 'standard candle' coming on. Rubbish? :-)
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: Ah, but some binary
)
OTOH, when taking precession and binary systems into account, the parameter search space gets more complicated, compared to what E@H is now looking for, I guess (target waveform at the source is a fairly simple sinus wave but with a slowly decaying (maybe also increasing) frequency, but is frequency and amplitude modulated at the detectors by the earth's movement around the sun and its rotation around its spin axis). Also the frequency of GW caused by presession and the movement of binary pulsars around their center of gravity are (I guess) not inside the favorable spectrum of ground based detectors (perhaps this is LISA territory).
??
CU
Bikeman
RE: RE: Ah, but some
)
Sorry, I was referring to upping their EM detection chances by flashing at us at least semi-regularly. We don't get "beamed" by GW's in that way. Quite right, as the GW frequency is of the order of twice whatever oscillation/modulation is occurring, and for precession that is likely to be ~ lowest frequency about in a binary system, then yes that's not the LIGO band.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal