summaryrefslogtreecommitdiffstats
path: root/physics
diff options
context:
space:
mode:
authorbryan newbold <bnewbold@snark.mit.edu>2008-07-13 02:00:24 -0400
committerbryan newbold <bnewbold@snark.mit.edu>2008-07-13 02:00:24 -0400
commit0b1a56db66d4dd7d8c19f1a1dc2aa5cd3f893227 (patch)
tree400cc27d29954620a143d8318bec16456c46f024 /physics
parentb3eca34d2f1c01e979e56ab91f9ef60d7775dd47 (diff)
downloadknowledge-0b1a56db66d4dd7d8c19f1a1dc2aa5cd3f893227.tar.gz
knowledge-0b1a56db66d4dd7d8c19f1a1dc2aa5cd3f893227.zip
spell checked some files; moved and added images; fixed some links; added warnings
Diffstat (limited to 'physics')
-rw-r--r--physics/LIGO48
-rwxr-xr-xphysics/fig/cross-section-diagram.jpgbin0 -> 1871788 bytes
-rw-r--r--physics/general relativity17
-rw-r--r--physics/gravitational waves56
4 files changed, 107 insertions, 14 deletions
diff --git a/physics/LIGO b/physics/LIGO
new file mode 100644
index 0000000..23fba64
--- /dev/null
+++ b/physics/LIGO
@@ -0,0 +1,48 @@
+=======================================================================
+LIGO: Laser Interferometer Gravitational Observatory
+=======================================================================
+
+.. warning:: This is a rough work in progress!! Likely to be factual errors, poor grammer, etc.
+
+.. note:: Most of this content is based on a 2002 Caltech course taught by
+ Kip Thorn [PH237]_
+
+Noise Sources
+~~~~~~~~~~~~~~~~~~~~~~
+
+For initial LIGO, seismic noise dominates below about 60Hz, suspension thermal
+noise between 60 and 180Hz, and radiation pressure shot noise above 180Hz.
+
+Sensitivity
+~~~~~~~~~~~~~~~~~~~~~
+
+Advanced LIGO will use 40kg sapphire test masses with sensitivity of about 10e-19 meters: 1/10000 of an atomic nucleus, 10e-13 of a wavelength, and half of the entire mirror's wave function.
+
+LISA
+~~~~~~~~~~~~~
+
+5e6 km separations between three spacecraft, 1 (astronomical unit, ~1.5e8 from the sun. 1 watt lasers.
+The heterodyne detection is of the beat frequencies at each spacecraft of the
+two incoming beams. Doppler shifts of spacecraft must be taken into account,
+due not only to sun radiation pressure etc, but varying gravitational fields
+from planetary orbits.
+
+The test masses inside LISA should be free falling and have relative
+separations stable to 10e-9 cm (10e-5 wavelength of light).
+
+LISA's sensitivity is in the milihertz regime.
+
+.. note: (insert LISA noise curve?)
+
+Data Analysis
+~~~~~~~~~~~~~~~~~~~~
+
+Using matched filtering (eg, take cross correlation between two waveforms,
+integrating their product), frequency sensitivity will be around the inverse
+of the number of cycles of waveform (for LIGO, around 20,000 cycles, for LISA
+around 200,000 cycles).
+
+This technique requires known, theoretically derived waveforms (within
+phase/amplitude). There are other methods when we don't have good guesses
+about the waveform we are looking for...
+
diff --git a/physics/fig/cross-section-diagram.jpg b/physics/fig/cross-section-diagram.jpg
new file mode 100755
index 0000000..13fdca5
--- /dev/null
+++ b/physics/fig/cross-section-diagram.jpg
Binary files differ
diff --git a/physics/general relativity b/physics/general relativity
new file mode 100644
index 0000000..9c2a90b
--- /dev/null
+++ b/physics/general relativity
@@ -0,0 +1,17 @@
+===========================
+General Relativity
+===========================
+
+.. warning:: This is a rough work in progress!! Likely to be factual errors,
+ poor grammer, etc.
+
+.. note:: Most of this content is based on a 2002 Caltech course taught by
+ Kip Thorn [PH237]_
+
+*See also `math/tensors </k/math/tensors>`_*
+
+
+References
+----------------
+
+.. [PH237] `Gravitational Waves`:title: (aka ph237), a course taught by Kip Thorne at Caltech in 2002. See http://elmer.tapir.caltech.edu/ph237/ for notes and lecture videos.
diff --git a/physics/gravitational waves b/physics/gravitational waves
index db2e667..81080c3 100644
--- a/physics/gravitational waves
+++ b/physics/gravitational waves
@@ -2,14 +2,14 @@
Gravitational Waves
=======================
-:Author: bnewbold@mit.edu
+.. warning:: This is a rough work in progress!! Likely to be factual errors, poor grammer, etc.
.. note:: Most of this content is based on a 2002 Caltech course taught by
Kip Thorn [PH237]_
Raw Info
-----------------
-Rank 4 Riemann tensors, will cover different gages.
+Rank 4 Riemann tensors, will cover different gauge.
Waves are double integrals of curvature tensor...
@@ -20,38 +20,66 @@ Invariance angles: (Spin of quantum particle) = :latex:`$2 pi$` / (invariance an
Graviton has :latex:`$\pi$` invariance angle, so it is spin 2; photons have unique :latex:`$\arrow{E}$` vector, so invariance angle is :latex:`$2\pi$`, spin 1
-Also describes spin by the group of lorentz transformations which effect propogation.
+Also describes spin by the group of Lorentz transformations which effect propagation.
-Two polarizations: cross and plus, corresponding to spin of particles aligning wiht or against propagation? (Ref: eugene vickner? reviews of modern physics)
+Two polarizations: cross and plus, corresponding to spin of particles aligning with or against propagation? (Ref: Eugene Vickner? reviews of modern physics)
-Waves' multipole order $\geq$ spin of quantum = 2 for graviton ((??))
+Waves' multipole order :latex:`$\geq$` spin of quantum = 2 for graviton ((??))
-Waves don't propogate like E, because mass monopoles don't oscillate like charges.
+Waves don't propagate like E, because mass monopoles don't oscillate like charges.
-:latex:`$ h \req \frac{G}{c^2} \frac{M_0}{r} + \frac{G}{c^3} \frac{M'_1}{r} + \frac{G}{c^4} \frac{M''_2}{r} + \frac{G}{c^4} \frac{S'_1}{r} + \frac{G}{c^5} \frac{S''_1}{r}$`
+:latex:`$ h \approx \frac{G}{c^2} \frac{M_0}{r} + \frac{G}{c^3} \frac{M'_1}{r} + \frac{G}{c^4} \frac{M''_2}{r} + \frac{G}{c^4} \frac{S'_1}{r} + \frac{G}{c^5} \frac{S''_1}{r}$`
First term: mass can't oscillate
Second term: momentum can't oscillate
-Third term: mass qudrupole moment dominates
+Third term: mass quadrupole moment dominates
Fourth term: angular momentum can't oscillate
Fifth term: current quadrupole
Energy
----------------
-Quick calculation: for a source with mass M, size L, period P, the quadupole moment $M_2 \req M L^2$, h \req 1/c^2 (newtonian potential energy) ????
+Quick calculation: for a source with mass M, size L, period P, the quadrupole moment $M_2 \approx M L^2$, h \approx 1/c^2 (Newtonian potential energy) ????
h on the order of $10^{-22}$
-Propogation
+Propagation
-----------------
-When wavelength much less than curvature of universe (background), then gravitational waves propagate like light waves: undergo red shifts, gravitational lensing, inflationary redshift, etc.
+When wavelength much less than curvature of universe (background), then gravitational waves propagate like light waves: undergo red shifts, gravitational lensing, inflationary red shift, etc.
+
+Sources
+-------------
+
+Inspirals of bodies into super-massive black holes
+ Eg, white dwarfs, neutron stars, small black holes.
+ Super-massive black holes are expected near the centers of galaxies.
+ Low frequencies (LISA); waveforms could hold data about spacetime curvature
+ local to the black hole.
+ Waveforms could be very difficult to predict.
+
+Binary black hole mergers
+ Broadband signals depending on masses.
+
+Neutron Star/Black hole mergers
+ Stellar mass objects existing in the main bodies of galaxies.
+ Higher frequencies (LIGO and AdvLIGO).
+
+Neutron Star/Neutron Star mergers
+ Have actual examples in our galaxy of these events; but final inspiral rate
+ is so low that we have must listen in other galaxies. Merger waves will
+ probably be lost in higher frequency noise, so can't probe local
+ gravitational curvature.
+ May observe "tails" of waves: scattering off of high curvature around the
+ binary.
+
+Pulsars (spinning neutron stars)
+ Known to exist in our galaxy.
Spectrum
----------------
High Frequency: Above 1 Hz, LIGO (10 Hz to 1kHz), resonant bars
- Small black holes (2 to 1k suns), neutron stars, supernovae
+ Small black holes (2 to 1k suns), neutron stars, supernovas
Low frequency: 1Hz and lower, LISA (10^-4 Hz to 0.1 Hz), Doppler tracking of spacecraft
Massive black holes (300 to 30 million suns), binary stars
@@ -63,12 +91,12 @@ Extreme Low Frequency: 10^-16 Hz, Cosmic Microwave Background anisotropy
Detectors
-----------------
-$\Delta L = h L \lreq 4 \times 10^{-16} \text{cm}$
+:m:`$\Delta L = h L ~ \leq 4 \times 10^{-16} \text{cm}$`
LIGO (10 Hz to 1kHz)
Also GEO, VIRGO, TAMA (?), AIGO
-LISA (10^-4 Hz to 0.1 Hz)
+LISA (10e-4 Hz to 0.1 Hz)
Resonant Bars
~~~~~~~~~~~~~~~