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Topic: Correlation function (astronomy)

	The Time Interferometer: Synthesis of the Correlation Function
		In the spectral-analysis case they are the power spectrum and the correlation function; in the interferometry their counterparts are the distribution of brightness and the spatial spectrum.
		Finally, equations which connect the quantities of the two levels are identical (convolution and multiplication) and include the characteristics of observations: the beam and the transfer function and their analogs, i.e., the spectral window and the correlation window.
		In optics or in radio astronomy, when filled apertures are used, the maps are produced directly in the focal plane of a telescope.
	www.cv.nrao.edu /adass/adassVI/vityazevv2.html (1267 words)

	Correlation function - Wikipedia, the free encyclopedia
		Cross correlations are a useful indicator of the dependencies among different random variables as a function of time.
		Correlation functions used in astronomy, financial analysis, quantum field theory and statistical mechanics differ only in the particular stochastic processes they are applied to with the caveat that we are dealing with "quantum distributions" in QFT.
		With these definitions, the study of correlation functions is equivalent to the study of probability distributions.
	en.wikipedia.org /wiki/Correlation_function (650 words)

	Space Astronomy
		The oldest of the three space disciplines, high-energy astronomy requires space observations because of the virtually total atmospheric absorption of high-energy photons and the destruction of high-energy cosmic-ray particles by the atmosphere.
		X-ray astronomy is truly a child of the space age; the first results came from a rocket flight in 1962, and not for several years was it generally apparent the X-ray observations represented an important aspect of astronomy.
		In contrast, ground-based optical astronomy suffers from the "twinkling" and from the scattering of light by the atmosphere.
	members.tripod.com /~worldsite/astronomy/spastro.html (5973 words)

	Cross Correlation (Site not responding. Last check: 2007-10-11)
		Cross correlation is a standard method of estimating the degree to which two series are correlated.
		When the correlation is calculated between a series and a lagged version of itself it is called autocorrelation.
		The Fourier transform of the cross correlation function is the product of the Fourier transform of the first series and the complex conjugate of the Fourier transform of the second series.
	astronomy.swin.edu.au /~pbourke/other/correlate (1162 words)

	Astronomy Information Portal @ Gazed.org (Site not responding. Last check: 2007-10-11)
		Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, "law of the stars") is the science of celestial objects (e.g.
		Modern astronomy is not to be confused with astrology, the belief system that claims human affairs are correlated with the positions of celestial objects.
		Modern astronomy has also discovered many exotic objects such as quasars, pulsars, blazars and radio galaxies, and has used these observations to develop physical theories which describe some of these objects in terms of equally exotic objects such as fl holes and neutron stars.
	www.gazed.org (2448 words)

	Astronomy In Art and Astro Art Information Portal @ AstronomyInArt.com (Site not responding. Last check: 2007-10-11)
		Astronomy is a science involving the observation and explanation of events occurring outside Earth and its atmosphere.
		It includes the study of the origin, evolution, and physical and chemical properties of objects that can be observed in the sky, space, and in the whole universe.
		Astronomy is the science of celestial objects such as stars, planets, comets and galaxies.
	www.astronomyinart.com (1535 words)

	WAPP Signal Processing Page
		The raw data produced by the WAPP are unsigned integers that represent estimates of correlation functions.
		The resulting correlation function has some addtional noise due to quantization that reduces SNR, hower this effect is modest and deemed a worth tradeoff.
		For the 3-level, we correlator SNR of the measured correlation fucntion, as compared to a sampler with inifinite quantizition is 81%, but this value only holds when the power level is ideal.
	www.naic.edu /~wapp/SignalProc/SPMain.htm (552 words)

	The Cosmic Distance Ladder II, Stars as Standard Candles (Site not responding. Last check: 2007-10-11)
		Parallax calibrates several secondary distance indicators, which are typically variable stars, whose role in distance determination is vital to extragalactic astronomy.
		In the early part of this century, Henrietta Leavitt, at Harvard College Observatory noticed a very interesting trend in particular variable stars which were similar in property to Delta Cephei, the fourth brightest star in the constellation Cepheus.
		She noticed that there was a correlation between the period of the brightness variation, and the brightness itself: the brighter the star, the longer its period.
	www.suite101.com /article.cfm/astronomy/13217 (460 words)

	NTIA Special Pub. 98-35: Radio Astronomy Spectrum Planning Options: Cover, Exec. Summary, & Foreword
		Radio astronomy is a relatively new radio service based on the reception of radio waves of cosmic origin through the use of radio telescopes.
		The recognition of radio astronomy as a radio service similar in stature to broadcasting or mobile radio communications was an historic step since it provided a legal basis for radio astronomy to seek protection against any “harmful” interference.
		Those bands for shared allocations are frequency bands of interest to radio astronomy and the bands for increased access are expansion of existing allocations to the minimum one percent bandwidth needed for adequate observations and research and for spectral-line observations.
	www.ntia.doc.gov /osmhome/reports/pub9835/Raspexec.htm (2676 words)

	Cosmos Astronomy
		At the subatomic levels we are all made of stardust.
		What the correlation of name to form suggests is a similar correlation in function.
		The fact that something in the heavens above, a nebula, resembles a horse, like the Horsehead Nebula suggests that there may also be a similar universal function comparable in some manner to the archetypal form of the horse or the evolutionary spiral of the horse...
	www.blessingscornucopia.com /Astronomical_Cosmological_Extraterrestrial.htm (604 words)

	Galaxies
		You can then discover a correlation between luminosity, mass, and temperature for main sequence stars that our physical theories must account for.
		Or you can calibrate the correlation between the width of the 21-cm line (neutral hydrogen emission line) and the spiral galaxy luminosity.
		There are number of beautiful objects that draw people to take up astronomy as a profession or a life-long hobby and the Sombrero Galaxy is one of them.
	www.astronomynotes.com /galaxy/s16.htm (1776 words)

	Basic Considerations (Site not responding. Last check: 2007-10-11)
		and the correlation function of the 1-bit quantized signal r(n) is less trivial and is given by the Van Vleck relationship [31]:
		-sample estimate of the correlation function is increased over what it would be for multibit correlation.
		In a one-bit correlator the number of samples should be increased by a factor of 2.46 to achieve the same accuracy as in the multibit method [28].
	pavel.physics.sunysb.edu /~sasha/docs/sasha/thesis/node16.html (567 words)

	phase correlation in EPR - Advanced Physics Forums (Site not responding. Last check: 2007-10-11)
		The mathematics showing the cause of EPR's correlation, the correlation of the internal phase of both particles, is given in - Found.
		The second is whether the causality of the correlation is a local or non-local effect.
		For example, even though the two photons of an "entangled" pair are physically separate, a polarization measurement (a phase dependent measurement) of the two particles must be correlated because their phase is correlated (within QM itself).
	www.advancedphysics.org /forum/showthread.php?t=5580 (2329 words)

	MAD Scientist: Gamma Camera (Site not responding. Last check: 2007-10-11)
		Considered as a function of the shift, the random pinhole mask has an auto-correlation function which is 0.5 at zero shift, and approximately 0.25 for all others.
		In particular, the random pinhole mask has an autocorrelation function which is only approximately constant (about 0.25) for non-zero shifts, because it depends on the exact number of holes that happen to line up, and that is random.
		Since any bumpiness in the auto-correlation function contributes noise to the image, such masks can be used to make more sensitive coded aperture instruments; but the principle for all is very similar.
	spider.ipac.caltech.edu /staff/waw/mad/mad8.html (1078 words)

	Essay (Site not responding. Last check: 2007-10-11)
		In extragalactic astronomy, the basic unit is a galaxy with a characteristic length of 20 kpc that typically moves within a group or clusters with diameter 50 kpc to 5 Mpc which in turn is located in a supercluster with diameter 50 Mpc or larger.
		In extragalactic astronomy, the three-dimensional region that constitutes a void is transparent and empty or nearly empty of galaxies.
		Estimates of the correlation function of galaxies indicate that
	www.astro.bas.bg /galaxies/galaxies_files/largescale.html (4423 words)

	[No title]
		The correlation function of clusters of galaxies and the amplitude of mass fluctuations in the Universe
		Correlation function as a measure of the structure.
		A 140 Mpc Oscillation of the Abell Cluster Correlation Function
	www.columbia.edu /~fms5/w381.html (1576 words)

	Evidence for the Big Bang
		Another way to think of temperature is as a measure of the speed that matter is travelling, albeit in an unordered, random manner (think of the air molecules in a balloon; they move around rapidly inside the balloon, but the balloon itself remains motionless).
		Another approach is Wald's "Hamiltonian" or "Hamilton function" for GR as derived in his GR text.
		Using data from the Sloan Digital Sky Survey, the positions of 200,000 quasars were correlated with the positions of 13 million galaxies.
	www.talkorigins.org /faqs/astronomy/bigbang.html (19835 words)

	Research
		Astronomy and Physics Research is a year-long course which will guide students through a series of authentic research projects involving physics and astronomy.
		The research projects will either be part of a larger organized project sponsored by a University or science center, or they will be independent projects which address topics determined by the student, teacher and a mentor.
		Tri Nguyen, Jerry Lancaster, and Robert Sullenger, 2003-2004's Astronomy and Physics Research class, took this picture of the central portion of the Orion Nebula in their first attempt at taking astrophotos using the school's telescope.
	homepage.mac.com /astronomyteacher/dvhs/research.html (1094 words)

	Arp and Two Point Angular Correlation Function - Bad Astronomy and Universe Today Forum
		The whole key to this, the whole key, is to compare the number of quasars near galaxies (for some definition of "near") to those in the field; far from galaxies.
		The function is a statistical measure of clumping of a distribution of objects.
		I distinctly remember reading a work by someone who applied this function and showed that the the function expected by Arp's distribution (which should show clumping on small angular scales), did not match the observed distribution of sources at the time.
	www.bautforum.com /showthread.php?t=6717 (4131 words)

	THE QURAN ON ASTRONOMY
		He disproved this and replied that what we are talking about is a branch of Astronomy called the "Integrated Cosmos" which we scientists have only come to know recently.
		For example, if you have a body in outer space which travels a certain distance in any direction and then travel the same distance in a different direction, you will find that the mass weight is the same in all directions.
		A correction must however be made to the absolutely circular form of its orbit, since modern astronomy ascribes a certain eccentricity to this, so that the distance between the Earth and the Moon (240,000 miles) is only the average distance.
	www.angelfire.com /in/islam/QURANASTRONOMY.html (8922 words)

	Pulse Arrival Time Algorithms
		The cross correlation function will measure the relative shift to within one phase bin of precision, but it is possible to extrapolate across the gaps in the discrete CCF using a simple mathematical function which can then be used to estimate the true shift.
		The apex of this parabola is taken to be the new point of maximum correlation.
		The error associated with this fit is somewhat difficult to determine analytically as it involves a component due to the intrinsic width of the parabola and also to the goodness of fit.
	astronomy.swin.edu.au /pulsar/algorithms (1065 words)

	Radio Astronomy Lecture Number 8
		Once we know the delay centers (delays needed to correlate a source directly overhead), then it is easy to calculate the correct delays for any other location in the sky, i.e.
		This is the function of an XF, or lag correlator, which first does many correlations (the X part) and then does a FT (the F part).
		The idea is that the incoming signal is divided up into different frequencies using a filterbank, and each of these signals is then correlated with all of the signals at the same frequency among all of the other antennas.
	web.njit.edu /~dgary/728/Lecture8.html (1910 words)

	University of Pittsburgh - Physics & Astronomy Department (Site not responding. Last check: 2007-10-11)
		This involves determining how the physical properties of galaxies change as a function of the age of the Universe as well as how galaxies cluster on the sky.
		With the new generation of large, multi-frequency imaging surveys now coming on line (such as the Sloan Digital Sky Survey www.sdss.org in which I am involved) we will soon have the first panchromatic view of the night sky.
		Prior to coming to the University of Pittsburgh I was a research scientist in the department of physics and astronomy at Johns Hopkins University (1993-1999).
	www.phyast.pitt.edu /People/Faculty/A_Connolly.htm (305 words)

	Re: Deja Vu Theory - Astronomy.com Forums
		There is a probable positive correlation between my drug usage and feelings of deja vu.
		I wonder with this age correlation is there also a correlation between the parents of the person in question (the one getting deja vue).
		So we have a paradox: on the one hand, the experiment shows that free will is illusory: it cannot be causing the brain events because the events kick in a second earlier.
	www.astronomy.com /ASY/CS/forums/3/297022/ShowPost.aspx (4332 words)

	Introduction to the Spectral Correlation Function
		In Radio Astronomy, we are now blessed with what some people might call "too much data." The Spectral Correlation Function (SCF) Project should give us a better understanding of what these data mean.
		In a nutshell, the SCF compares observations of the distribution of velocities of gas particles in space, and it can be used to compare the observed distributions with theoretically prediced ones.
		Thus, even though the inherently four-dimensional (position-position-intensity-velocity) set of observations has now been reduced to three dimensions, the new third dimension, S_0, includes information about both of the dimensions (intensity and velocity) it replaces, so all dimensions are essentially preserved.
	cfa-www.harvard.edu /~agoodman/scf/intro/intro_scf.html (661 words)

	Coherence
		Because of the randomness of the parameters which describe the arriving light, the correlation between light arriving at the pinhole at any instant, and light arriving just a bit later cannot be expected to be large.
		Each photon contributes a brief sinusoidal pulse of energy, modulated in a gaussian manner, the duration of which depends on the atomic transition or collision mechanism which produced it.
		For a disc-like source like a star, the coherence, or correlation function, is a first order Bessel function.
	mysite.verizon.net /chrisrbrown/id4.html (717 words)

	Observable physical properties of galaxies (Site not responding. Last check: 2007-10-11)
		There is an obvious correlation for B/D, but note there is large range of B/D within any given morphological class.
		Galaxy luminosity functions: let's further consider the range of luminosities found in galaxies, both overall and as a function of morphological type.
		In addition, the luminosity function of galaxies is an important cosmological probe for evolution of the galaxy population, as we'll discuss more later.
	astronomy.nmsu.edu /holtz/a616/ay616/node3.html (1054 words)

	ADASS 2003 Conference Proceedings
		We have developed a class of algorithms which dramatically reduce the algorithmic complexity for such problems: it is the extension of the previous single-tree methods to a new class we call multi-tree methods (Gray, 2003).
		The spherical kernel corresponds exactly to the range-counting problem as described earlier, but because the Gaussian function does not have finite extent, our previous notion of pruning must be extended to one of approximation, which will not be described here for lack of space.
		In general we refer to this quantity in place of the full correlation function since it is what we need to concern ourselves with computationally.
	www.adass.org /adass/proceedings/adass03/O3-2 (1234 words)

	Handbook of Chemistry and Physics - Web Edition
		Thermal Conductivity of Alloys as a Function of Temperature
		Thermal Conductivity of Metals and Semiconductors as a Function of Temperature
		Density of Solvents as a Function of Temperature
	www.hbcpnetbase.com /search/searchresult.asp (543 words)

	Real-space analysis of neutron diffuse scattering from α-AgI
		AgI are mainly due to Laue monotonic scattering rather than to interionic correlations.
		Of most importance is the fact that the Patterson function has to be taken into account to evaluate the correct pair correlation function in the fast-ion conductor.
		A gas-like correlation function is obtained for Ag-Ag pairs.
	www.iop.org /EJ/abstract/0022-3719/20/31/005 (280 words)

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