Latex Template of sending poster's abstract for % the Heidelberg Symposium on % ``High Energy Gamma-Ray Astronomy'' % June 26-30, 2000, Heidelberg, Germany % % Send abstracts for the poster session to: % HDGS@mpi-hd.mpg.de % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % This template is available at the web site, % http://www.mpi-hd.mpg.de/voelk/hdgs % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \documentclass[11pt,dvips]{article} \usepackage{epsfig,times} % If you are using LaTeX2.09 please use two lines below instead of % two lines above. % \documentstyle[11pt]{article} % \include{epsfig,times} % % Setting various length parameters (DO NOT ALTER): % \setlength{\textwidth}{150mm} \setlength{\textheight}{260mm} \setlength{\topmargin}{-10mm} \setlength{\oddsidemargin}{5mm} \setlength{\evensidemargin}{5mm} \setlength{\parindent}{0pt} % % It is required that there be no pagination (DO NOT ALTER): % \pagestyle{empty} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % Beginning of Document: % \begin{document} % % Session and Paper Code: % \thispagestyle{myheadings} % % ***INSTRUCTIONS:*** Replace `GS' in the command argument below % with your assigned session: % % GS - Galactic Sources % ES - Extragalactic Sources % PA - Particle Acceleration Models % OC - Observational cosmology with Gamma Rays % BL - Gamma-Ray Blazars % GA - Sensitivity Threshold of Ground-Based Gamma-Ray Astronomy % \markright{GS:PA} % % Title: % \begin{center} % % ***INSTRUCTIONS:*** Replace `Instructions for Preparation of Abstract' % with your abstract's title: % {\LARGE \bf Antigravity Theory } \end{center} % % Author List:E.Valbonesi % \begin{center} % % ***INSTRUCTIONS:*** Replace authors and addresses below with your own: % {\bf }\\ {\it \\ $^ Author ENRICO VALBONESI } \end{center} % Abstract: \begin{center} {\large \bf Abstract\\} The modelling of antigravity dont'is new. \end{center} \vspace{-0.5ex} % % ***INSTRUCTIONS:*** Replace text below with your own abstract: % the target that I am trying to realize and the demonstration that in the introno of the black holes not are caused phenomena of jet from elevations of the temperature but from caused phenomena of resonance from the emission from part of the black hole of a bundle of cancellations that hit with a sinuisoidale frequency the aglomerates one of particles that are along the wings. it agglomerates you of particles in conditions of high density after the borbandamento of cancellations from part of the black hole will give origin to the emissions of the get of high energy. > italian version l'obbiettivo che sto cercando di realizzare e la dimostrazione che nell'introno dei buchi neri non ci sono fenomeni di jet causati da innalzamenti della temperatura . ma da fenomeni di risonanza causati dall'emissione da parte del buco nero di un fascio di radiazioni che colpiscono con una frequenza sinuisoidale l'aglomerato di particelle che sono lungo le ali . gli agglomerati di particelle in condizioni di alta densita' dopo il borbandamento di radiazioni da parte del buco nero daranno origine alle emissioni dei get di alta energia. you will send the article second the detailed lists of American Intitute of Physics vi mandero' l'articolo secondo le specifiche Dell' American Intitute of Physics dott. Enrico Valbonesi e-mail valbones@uniroma3.it % % Leave this line skip in place: \vspace{1ex} \end{document} Per capire questo ti[po di onde isogna capire che sono onde di energia gia' estrinsecate come rumore di fondo A team of researchers that looked at data from more than 140,000 galaxies says the universe is far from heavy and has a density of next to nothing. "It's about 300 billion billion billion times less dense than water," said John Peacock of the University of Edinburgh, "or one ten-thousandth of an ounce in a volume the same size as the Earth." Take a video journey through the galaxies. Peacock and his colleagues got the answer using an instrument on the Anglo-Australian Telescope that can detect the light from 400 galaxies simultaneously over a field of view four times as wide as the full Moon. The research is part of a massive effort to create a three-dimensional map of the universe. The instrument shows the "redshift" of each galaxy (i.e., the extent to which galactic light turns reddish as the galaxy moves away from the observer), thereby suggesting the galaxies' relative distance to Earth. That determination leads to the calculation of each galaxy's density and mass, and also those properties of the universe. The results were published in the March 8, 2001, issue of the journal Nature. Supercluster collapse The analysis also claims to clarify astronomers' understanding of the structure of the universe throughout which galaxies are sprinkled not randomly, but in clusters that glom together in "superclusters." Peacock and his colleagues found that superclusters form, as suspected, from the inward gravitational collapse of galaxies upon one another. To get the density figure, the team looked at "peculiar" velocities created when the superclusters tug and pull on nearby galaxies whizzing by. That led them to calculate that the universe is one third as populated as the calculated density that would halt an expanding universe. Most theorists now agree the universe is expanding as a result of the Big Bang -- the explosive instant thought to have given birth to the universe. "The actual figure is tiny," said Peacock, "about 3 times 10^{-27} kilograms per cubic meter." That's much, much lighter -- a fraction of a three kilograms with 27 zeroes in front of the decimal point -- than a dust speck in a bucket the size of a wide-screen TV for a typical home. Survey finished later this year The results come from an ambitious effort, called the 2dF Galaxy Redshift Survey, to detect light simultaneously from hundreds of galaxies at a time. Eventually, the survey, conducted by British and Australian researchers, will yield an inventory of about 10 percent of the galaxies in Earth's cosmic neighborhood. It will map one-tenth of the galaxies within 2 billion light-years of Earth (a light-year is the distance light travels in a year -- about 6 trillion miles or 9.7 trillion kilometers). Last year, project scientists used earlier data from the survey to show that the universe will continue to expand forever, rather than end in a catastrophic collision like the opposite of the Big Bang. Peacock is optimistic that future analyses of 2dF data will yield the "fluctuation spectrum" -- jargon for how clumpy the distribution of galaxies is in the universe. "This can not only give us another independent way to measure the mass density," he said, "it can also tell us what fraction of this mass is in the form of ordinary matter (particles like electrons and protons -- the same as you are), as opposed to exotic elementary particles left over as relics from the earliest phases of the Big Bang." The survey, which should be done later this year after completing the logging of data on 250,000 galaxies, has involved a vast array of astronomical talent, including instrument designers and engineers, observational astronomers and theorists who have cranked out statistics on the results. (Other sky surveys currently under way include the 2MASS Redshift Survey and the Sloan Digital Sky Survey.) "The end result is something that no individual could have produced unaided," Peacock said. Marc Davis of the University of California, who wrote an accompanying article in Nature on the new study, heralded the analysis as moving cosmology to a new and more sophisticated level of analysis. "Cosmology, long considered a branch of philosophy rather than physics because of the dearth of data, has made dramatic progress in the past few years and is now entering an era of large-scale studies and precision measurements," he said. X-Ray Spectra Help Astronomers Hunt Cosmic Monsters By The European Space Agency posted: 06:27 am ET 08 March 2001 One must admit that spectra, the curves that plot the number of photons and their energy, appear to be rather uninspiring to the layman -- There's nothing worse than a graph! But like one?s body temperature curve, they mean a lot. For astronomers, spectra are like fingerprints from the stars and galaxies. The information they hold may be incomplete, like a tattered newspaper, but it tells a story. While images from a telescope are attractive, spectra can reveal the innermost secrets of certain cosmic monsters. The image of XMM-Newton?s deepest observation of the "blank" X-ray sky in the direction of the Lockman Hole -- where X-ray absorbing extragalactic material is thinnest and one can best peek into the confines of the universe -- has already been acclaimed. The picture identifies about 150 new X-ray sources, most of them among the faintest hard X-ray sources ever observed. Many of the brighter X-ray emissions in the Lockman Hole were previously identified with the ROSAT satellite. For these, XMM-Newton has now provided very detailed spectra, as is shown in a picture montage by Guenther Hasinger from the Astrophysics Institute of Potsdam (AIP). (courtesy Guenther Hasinger/AIP -- click to enlarge) The main image [above] plots the soft X-ray photons, already observed by ROSAT, in red. Green corresponds to intermediate X-ray photons, also detectable by NASA?s Chandra X-ray Observatory. Blue is used to show the hardest X-ray photons, only detectable by XMM-Newton. The individual spectra [right edge of this page] "roll out" this color information into graphs, plotted in red, where the X-ray emission (the number of arriving photons) is plotted against the energy at which it is emitted. The green lines refer to model spectra fitted to these graphs. Many of the sources are associated with black holes, monstrous gravitational wells into which matter is being sucked and in which even light disappears. Stellar-mass black holes arise after the death of a massive star that has used all its fuel. But there exist also supermassive black holes, which are present in the center of almost every galaxy. "The origin of these supermassive ones remains a complete mystery," said Guenther Hasinger. "Forming these from many single black holes would probably take too much time. They might therefore be part of the original collapse of gas into a galaxy, in other words the seed objects of galaxy creation." Next page: detectives of the invisible universe X-Ray Spectra Help Astronomers Hunt Cosmic Monsters (cont.) Detectives of the invisible The spectra of the X-ray emission from the sources can reveal a lot about the properties of the active nucleus. If low-energy X-rays are sparse compared with those at higher energies, it indicates that there is much absorbing gas between us and the nucleus -- or possible black hole. The absorbing material may be in a ring or doughnut shape, surrounding the X-ray source. In some extreme cases, when we are looking at this accretion disk edge-on, the nucleus may be hidden from our view, and only the highest energy X-rays can escape. Alternatively when there is little absorption, and the low-energy X-rays are strong, the spectra display practically straight lines (known as "power-law spectra"). They indicate that we are getting a close-to-face-on view, looking right down into the nucleus and associated black hole. Other sources show bumps or wiggles in their spectra. This can be attributed to the emission of iron atoms very close to the maelstrom of the black hole. From the shape of a bump, one can infer the geometry of the emitting region -- for instance, our distance from the hole and the angle at which we are observing the central accretion disk. Clearly identified emission lines in the spectra are the fingerprints of different elements that are swirling around very close to the event horizon, where matter finally disappears. From the displacement of these lines from their normal position in a spectrum one can measure the velocities, close to the speed of light, at which these atoms are moving. This, in turn, indicates how fast the black hole itself is rotating. An iron line also tells us how close the accretion disk is reaching to the very edge of the black hole. A new black hole? "All but one of these nine sources had already been identified by ROSAT. Whether they are unobscured sources with straight power-law profiles, or objects whose X-rays are partially absorbed, the XMM-Newton spectra confirm the models -- the way we had imagined we would see these sources in greater detail," explained Guenther Hasinger. "But the bright source -- practically in the center of the image -- is one of XMM-Newton?s new discoveries! "We have given it the number 24021. Its nature is still unclear; it has a very different spectrum, practically no X-rays below the 2 keV energy level and a power-law profile above 2 keV. We haven?t determined its redshift (how far away it is), and to know more we will need to observe this source with the new generation of 8- to 10-meter (315- to 395-inch) telescopes." Those who say spectra are dull must be lacking in imagination. The spectral fingerprints like those shown here are revealing how black holes form and grow. If the Lockman Hole observation is an example, XMM-Newton?s spectrometric mission promises to be extremely rewarding. Next page: detectives of the invisible universe X-Ray Spectra Help Astronomers Hunt Cosmic Monsters (cont.) quinataeesenza: Missing Energy Quintessence (Q) Cosmological Constant (L) W? Quintessence* negative pressure (p) or -1 < w = p/r < 0 time-varying p and r spatially inhomogeneous Caldwell, Dave, PJS. (1998)* Why quintessence? logical possibility that is physically distinct from L excellent fit to current data may solve the ?cosmic coincidence problem? Examples scalar field Q rolling down a potential V(Q) pressure = K.E. - P.E. Slow-roll: K.E. << P.E. or p < 0 W = KE - PE KE + PE Quintessence = equation-of-state Weiss (1987), Ratra & Peebles(1988), Wetterich (1995), Frieman et al (1995), Coble et al (1997), Ferreira & Joyce (1997), Caldwell et al. (1998), ... W can be constant, monotonically increasing or decreasing, or oscillatory Examples web of nonabelian cosmic strings network of nonabelian domain walls W = - 1/3 Quintessence Kamionkowski & Toumbas (1996), Spergel & Pen. (1997), Bucher & Spergel (1998), W = - 2/3 Summary of Evidence for an Exotic Energy Component (Quintessence or Cosmological Constant) L or Q Sum rule: 1 = Wm + Wk + W? Quintessence vs. Cosmological Constant from Wang,Caldwell, Ostriker & PJS (1999) See also Workshop Talk by Robert Caldwell and Poster by Limin Wang see also Turner, Perlmutter and White (1999) Observational Differences COBE + low red shift tests COBE: COBE norm of the mass power spectrum ns: spectral tilt s8: cluster abundance peculiar velocities SHAPE shape of mass power spectrum on scales > 10 Mpc H+BBN+BF: Hubble parameter + Big Bang Nucleosynthesis + Baryon Fraction Bulk Flow Age Observational Differences Conclusions: Both cosmological constant and quintessence fit current observations well Best hopes for discrimination: - CMB anisotropy - Supernovae - gravitational lens statistics (esp. arcs) Quintessence vs. Cosmological Constant Theoretical Advantages The Quintessential Solution: Tracker Fields & Tracker Solutions Zlatev, Wang, & PJS (1998); PJS, Wang,Zlatev (1999) See also Poster by Ivaylo Zlatev For a wide class of potentials G = V? V/(V? 2) > 5/6 and nearly constant The Quintessential Solution: there are attractor solutions to the equations of motion which lead to cosmic acceleration today nearly independent of initial conditions ! Tracker potential: V(Q) = M4 f(Q/M) The Quintessential Solution: The values of WQ and Wm are determined by M Trackers: New Prediction Wm - w relation More Exotic Possibilities ? Evidence mounting Curvature disfavored but still uncertain at present Near-future cosmological observations may decide the issue Profound implications for cosmology & fundamental physics New Problems (?coincidence?) and perhaps novel solutions (?trackers?) and new predictions (Wm - w relation) Per capire questo ti[po di onde isogna capire che sono onde di energia gia' estrinsecate come rumore di fondo A team of researchers that looked at data from more than 140,000 galaxies says the universe is far from heavy and has a density of next to nothing. "It's about 300 billion billion billion times less dense than water," said John Peacock of the University of Edinburgh, "or one ten-thousandth of an ounce in a volume the same size as the Earth." Take a video journey through the galaxies. Peacock and his colleagues got the answer using an instrument on the Anglo-Australian Telescope that can detect the light from 400 galaxies simultaneously over a field of view four times as wide as the full Moon. The research is part of a massive effort to create a three-dimensional map of the universe. The instrument shows the "redshift" of each galaxy (i.e., the extent to which galactic light turns reddish as the galaxy moves away from the observer), thereby suggesting the galaxies' relative distance to Earth. That determination leads to the calculation of each galaxy's density and mass, and also those properties of the universe. The results were published in the March 8, 2001, issue of the journal Nature. Supercluster collapse The analysis also claims to clarify astronomers' understanding of the structure of the universe throughout which galaxies are sprinkled not randomly, but in clusters that glom together in "superclusters." Peacock and his colleagues found that superclusters form, as suspected, from the inward gravitational collapse of galaxies upon one another. To get the density figure, the team looked at "peculiar" velocities created when the superclusters tug and pull on nearby galaxies whizzing by. That led them to calculate that the universe is one third as populated as the calculated density that would halt an expanding universe. Most theorists now agree the universe is expanding as a result of the Big Bang -- the explosive instant thought to have given birth to the universe. "The actual figure is tiny," said Peacock, "about 3 times 10^{-27} kilograms per cubic meter." That's much, much lighter -- a fraction of a three kilograms with 27 zeroes in front of the decimal point -- than a dust speck in a bucket the size of a wide-screen TV for a typical home. Survey finished later this year The results come from an ambitious effort, called the 2dF Galaxy Redshift Survey, to detect light simultaneously from hundreds of galaxies at a time. Eventually, the survey, conducted by British and Australian researchers, will yield an inventory of about 10 percent of the galaxies in Earth's cosmic neighborhood. It will map one-tenth of the galaxies within 2 billion light-years of Earth (a light-year is the distance light travels in a year -- about 6 trillion miles or 9.7 trillion kilometers). Last year, project scientists used earlier data from the survey to show that the universe will continue to expand forever, rather than end in a catastrophic collision like the opposite of the Big Bang. Peacock is optimistic that future analyses of 2dF data will yield the "fluctuation spectrum" -- jargon for how clumpy the distribution of galaxies is in the universe. "This can not only give us another independent way to measure the mass density," he said, "it can also tell us what fraction of this mass is in the form of ordinary matter (particles like electrons and protons -- the same as you are), as opposed to exotic elementary particles left over as relics from the earliest phases of the Big Bang." The survey, which should be done later this year after completing the logging of data on 250,000 galaxies, has involved a vast array of astronomical talent, including instrument designers and engineers, observational astronomers and theorists who have cranked out statistics on the results. (Other sky surveys currently under way include the 2MASS Redshift Survey and the Sloan Digital Sky Survey.) "The end result is something that no individual could have produced unaided," Peacock said. Marc Davis of the University of California, who wrote an accompanying article in Nature on the new study, heralded the analysis as moving cosmology to a new and more sophisticated level of analysis. "Cosmology, long considered a branch of philosophy rather than physics because of the dearth of data, has made dramatic progress in the past few years and is now entering an era of large-scale studies and precision measurements," he said. X-Ray Spectra Help Astronomers Hunt Cosmic Monsters By The European Space Agency posted: 06:27 am ET 08 March 2001 One must admit that spectra, the curves that plot the number of photons and their energy, appear to be rather uninspiring to the layman -- There's nothing worse than a graph! But like one?s body temperature curve, they mean a lot. For astronomers, spectra are like fingerprints from the stars and galaxies. The information they hold may be incomplete, like a tattered newspaper, but it tells a story. While images from a telescope are attractive, spectra can reveal the innermost secrets of certain cosmic monsters. The image of XMM-Newton?s deepest observation of the "blank" X-ray sky in the direction of the Lockman Hole -- where X-ray absorbing extragalactic material is thinnest and one can best peek into the confines of the universe -- has already been acclaimed. The picture identifies about 150 new X-ray sources, most of them among the faintest hard X-ray sources ever observed. Many of the brighter X-ray emissions in the Lockman Hole were previously identified with the ROSAT satellite. For these, XMM-Newton has now provided very detailed spectra, as is shown in a picture montage by Guenther Hasinger from the Astrophysics Institute of Potsdam (AIP). (courtesy Guenther Hasinger/AIP -- click to enlarge) The main image [above] plots the soft X-ray photons, already observed by ROSAT, in red. Green corresponds to intermediate X-ray photons, also detectable by NASA?s Chandra X-ray Observatory. Blue is used to show the hardest X-ray photons, only detectable by XMM-Newton. The individual spectra [right edge of this page] "roll out" this color information into graphs, plotted in red, where the X-ray emission (the number of arriving photons) is plotted against the energy at which it is emitted. The green lines refer to model spectra fitted to these graphs. Many of the sources are associated with black holes, monstrous gravitational wells into which matter is being sucked and in which even light disappears. Stellar-mass black holes arise after the death of a massive star that has used all its fuel. But there exist also supermassive black holes, which are present in the center of almost every galaxy. "The origin of these supermassive ones remains a complete mystery," said Guenther Hasinger. "Forming these from many single black holes would probably take too much time. They might therefore be part of the original collapse of gas into a galaxy, in other words the seed objects of galaxy creation." Next page: detectives of the invisible universe X-Ray Spectra Help Astronomers Hunt Cosmic Monsters (cont.) Detectives of the invisible The spectra of the X-ray emission from the sources can reveal a lot about the properties of the active nucleus. If low-energy X-rays are sparse compared with those at higher energies, it indicates that there is much absorbing gas between us and the nucleus -- or possible black hole. The absorbing material may be in a ring or doughnut shape, surrounding the X-ray source. In some extreme cases, when we are looking at this accretion disk edge-on, the nucleus may be hidden from our view, and only the highest energy X-rays can escape. Alternatively when there is little absorption, and the low-energy X-rays are strong, the spectra display practically straight lines (known as "power-law spectra"). They indicate that we are getting a close-to-face-on view, looking right down into the nucleus and associated black hole. Other sources show bumps or wiggles in their spectra. This can be attributed to the emission of iron atoms very close to the maelstrom of the black hole. From the shape of a bump, one can infer the geometry of the emitting region -- for instance, our distance from the hole and the angle at which we are observing the central accretion disk. Clearly identified emission lines in the spectra are the fingerprints of different elements that are swirling around very close to the event horizon, where matter finally disappears. From the displacement of these lines from their normal position in a spectrum one can measure the velocities, close to the speed of light, at which these atoms are moving. This, in turn, indicates how fast the black hole itself is rotating. An iron line also tells us how close the accretion disk is reaching to the very edge of the black hole. A new black hole? "All but one of these nine sources had already been identified by ROSAT. Whether they are unobscured sources with straight power-law profiles, or objects whose X-rays are partially absorbed, the XMM-Newton spectra confirm the models -- the way we had imagined we would see these sources in greater detail," explained Guenther Hasinger. "But the bright source -- practically in the center of the image -- is one of XMM-Newton?s new discoveries! "We have given it the number 24021. Its nature is still unclear; it has a very different spectrum, practically no X-rays below the 2 keV energy level and a power-law profile above 2 keV. We haven?t determined its redshift (how far away it is), and to know more we will need to observe this source with the new generation of 8- to 10-meter (315- to 395-inch) telescopes." Those who say spectra are dull must be lacking in imagination. The spectral fingerprints like those shown here are revealing how black holes form and grow. If the Lockman Hole observation is an example, XMM-Newton?s spectrometric mission promises to be extremely rewarding. Next page: detectives of the invisible universe X-Ray Spectra Help Astronomers Hunt Cosmic Monsters (cont.) quinataeesenza: Missing Energy Quintessence (Q) Cosmological Constant (L) W? Quintessence* negative pressure (p) or -1 < w = p/r < 0 time-varying p and r spatially inhomogeneous Caldwell, Dave, PJS. (1998)* Why quintessence? logical possibility that is physically distinct from L excellent fit to current data may solve the ?cosmic coincidence problem? Examples scalar field Q rolling down a potential V(Q) pressure = K.E. - P.E. Slow-roll: K.E. << P.E. or p < 0 W = KE - PE KE + PE Quintessence = equation-of-state Weiss (1987), Ratra & Peebles(1988), Wetterich (1995), Frieman et al (1995), Coble et al (1997), Ferreira & Joyce (1997), Caldwell et al. (1998), ... W can be constant, monotonically increasing or decreasing, or oscillatory Examples web of nonabelian cosmic strings network of nonabelian domain walls W = - 1/3 Quintessence Kamionkowski & Toumbas (1996), Spergel & Pen. (1997), Bucher & Spergel (1998), W = - 2/3 Summary of Evidence for an Exotic Energy Component (Quintessence or Cosmological Constant) L or Q Sum rule: 1 = Wm + Wk + W? Quintessence vs. Cosmological Constant from Wang,Caldwell, Ostriker & PJS (1999) See also Workshop Talk by Robert Caldwell and Poster by Limin Wang see also Turner, Perlmutter and White (1999) Observational Differences COBE + low red shift tests COBE: COBE norm of the mass power spectrum ns: spectral tilt s8: cluster abundance peculiar velocities SHAPE shape of mass power spectrum on scales > 10 Mpc H+BBN+BF: Hubble parameter + Big Bang Nucleosynthesis + Baryon Fraction Bulk Flow Age Observational Differences Conclusions: Both cosmological constant and quintessence fit current observations well Best hopes for discrimination: - CMB anisotropy - Supernovae - gravitational lens statistics (esp. arcs) Quintessence vs. Cosmological Constant Theoretical Advantages The Quintessential Solution: Tracker Fields & Tracker Solutions Zlatev, Wang, & PJS (1998); PJS, Wang,Zlatev (1999) See also Poster by Ivaylo Zlatev For a wide class of potentials G = V? V/(V? 2) > 5/6 and nearly constant The Quintessential Solution: there are attractor solutions to the equations of motion which lead to cosmic acceleration today nearly independent of initial conditions ! Tracker potential: V(Q) = M4 f(Q/M) The Quintessential Solution: The values of WQ and Wm are determined by M Trackers: New Prediction Wm - w relation More Exotic Possibilities ? Evidence mounting Curvature disfavored but still uncertain at present Near-future cosmological observations may decide the issue Profound implications for cosmology & fundamental physics New Problems (?coincidence?) and perhaps novel solutions (?trackers?) and new predictions (Wm - w relation) web site : http://feynman.princeton.edu/~steinh/pritzker/tsld041.htm Per capire questo ti[po di onde isogna capire che sono onde di energia gia' estrinsecate come rumore di fondo A team of researchers that looked at data from more than 140,000 galaxies says the universe is far from heavy and has a density of next to nothing. "It's about 300 billion billion billion times less dense than water," said John Peacock of the University of Edinburgh, "or one ten-thousandth of an ounce in a volume the same size as the Earth." Take a video journey through the galaxies. Peacock and his colleagues got the answer using an instrument on the Anglo-Australian Telescope that can detect the light from 400 galaxies simultaneously over a field of view four times as wide as the full Moon. The research is part of a massive effort to create a three-dimensional map of the universe. The instrument shows the "redshift" of each galaxy (i.e., the extent to which galactic light turns reddish as the galaxy moves away from the observer), thereby suggesting the galaxies' relative distance to Earth. That determination leads to the calculation of each galaxy's density and mass, and also those properties of the universe. The results were published in the March 8, 2001, issue of the journal Nature. Supercluster collapse The analysis also claims to clarify astronomers' understanding of the structure of the universe throughout which galaxies are sprinkled not randomly, but in clusters that glom together in "superclusters." Peacock and his colleagues found that superclusters form, as suspected, from the inward gravitational collapse of galaxies upon one another. To get the density figure, the team looked at "peculiar" velocities created when the superclusters tug and pull on nearby galaxies whizzing by. That led them to calculate that the universe is one third as populated as the calculated density that would halt an expanding universe. Most theorists now agree the universe is expanding as a result of the Big Bang -- the explosive instant thought to have given birth to the universe. "The actual figure is tiny," said Peacock, "about 3 times 10^{-27} kilograms per cubic meter." That's much, much lighter -- a fraction of a three kilograms with 27 zeroes in front of the decimal point -- than a dust speck in a bucket the size of a wide-screen TV for a typical home. Survey finished later this year The results come from an ambitious effort, called the 2dF Galaxy Redshift Survey, to detect light simultaneously from hundreds of galaxies at a time. Eventually, the survey, conducted by British and Australian researchers, will yield an inventory of about 10 percent of the galaxies in Earth's cosmic neighborhood. It will map one-tenth of the galaxies within 2 billion light-years of Earth (a light-year is the distance light travels in a year -- about 6 trillion miles or 9.7 trillion kilometers). Last year, project scientists used earlier data from the survey to show that the universe will continue to expand forever, rather than end in a catastrophic collision like the opposite of the Big Bang. Peacock is optimistic that future analyses of 2dF data will yield the "fluctuation spectrum" -- jargon for how clumpy the distribution of galaxies is in the universe. "This can not only give us another independent way to measure the mass density," he said, "it can also tell us what fraction of this mass is in the form of ordinary matter (particles like electrons and protons -- the same as you are), as opposed to exotic elementary particles left over as relics from the earliest phases of the Big Bang." The survey, which should be done later this year after completing the logging of data on 250,000 galaxies, has involved a vast array of astronomical talent, including instrument designers and engineers, observational astronomers and theorists who have cranked out statistics on the results. (Other sky surveys currently under way include the 2MASS Redshift Survey and the Sloan Digital Sky Survey.) "The end result is something that no individual could have produced unaided," Peacock said. Marc Davis of the University of California, who wrote an accompanying article in Nature on the new study, heralded the analysis as moving cosmology to a new and more sophisticated level of analysis. "Cosmology, long considered a branch of philosophy rather than physics because of the dearth of data, has made dramatic progress in the past few years and is now entering an era of large-scale studies and precision measurements," he said. X-Ray Spectra Help Astronomers Hunt Cosmic Monsters By The European Space Agency posted: 06:27 am ET 08 March 2001 One must admit that spectra, the curves that plot the number of photons and their energy, appear to be rather uninspiring to the layman -- There's nothing worse than a graph! But like one?s body temperature curve, they mean a lot. For astronomers, spectra are like fingerprints from the stars and galaxies. The information they hold may be incomplete, like a tattered newspaper, but it tells a story. While images from a telescope are attractive, spectra can reveal the innermost secrets of certain cosmic monsters. The image of XMM-Newton?s deepest observation of the "blank" X-ray sky in the direction of the Lockman Hole -- where X-ray absorbing extragalactic material is thinnest and one can best peek into the confines of the universe -- has already been acclaimed. The picture identifies about 150 new X-ray sources, most of them among the faintest hard X-ray sources ever observed. Many of the brighter X-ray emissions in the Lockman Hole were previously identified with the ROSAT satellite. For these, XMM-Newton has now provided very detailed spectra, as is shown in a picture montage by Guenther Hasinger from the Astrophysics Institute of Potsdam (AIP). (courtesy Guenther Hasinger/AIP -- click to enlarge) The main image [above] plots the soft X-ray photons, already observed by ROSAT, in red. Green corresponds to intermediate X-ray photons, also detectable by NASA?s Chandra X-ray Observatory. Blue is used to show the hardest X-ray photons, only detectable by XMM-Newton. The individual spectra [right edge of this page] "roll out" this color information into graphs, plotted in red, where the X-ray emission (the number of arriving photons) is plotted against the energy at which it is emitted. The green lines refer to model spectra fitted to these graphs. Many of the sources are associated with black holes, monstrous gravitational wells into which matter is being sucked and in which even light disappears. Stellar-mass black holes arise after the death of a massive star that has used all its fuel. But there exist also supermassive black holes, which are present in the center of almost every galaxy. "The origin of these supermassive ones remains a complete mystery," said Guenther Hasinger. "Forming these from many single black holes would probably take too much time. They might therefore be part of the original collapse of gas into a galaxy, in other words the seed objects of galaxy creation." Next page: detectives of the invisible universe X-Ray Spectra Help Astronomers Hunt Cosmic Monsters (cont.) Detectives of the invisible The spectra of the X-ray emission from the sources can reveal a lot about the properties of the active nucleus. If low-energy X-rays are sparse compared with those at higher energies, it indicates that there is much absorbing gas between us and the nucleus -- or possible black hole. The absorbing material may be in a ring or doughnut shape, surrounding the X-ray source. In some extreme cases, when we are looking at this accretion disk edge-on, the nucleus may be hidden from our view, and only the highest energy X-rays can escape. Alternatively when there is little absorption, and the low-energy X-rays are strong, the spectra display practically straight lines (known as "power-law spectra"). They indicate that we are getting a close-to-face-on view, looking right down into the nucleus and associated black hole. Other sources show bumps or wiggles in their spectra. This can be attributed to the emission of iron atoms very close to the maelstrom of the black hole. From the shape of a bump, one can infer the geometry of the emitting region -- for instance, our distance from the hole and the angle at which we are observing the central accretion disk. Clearly identified emission lines in the spectra are the fingerprints of different elements that are swirling around very close to the event horizon, where matter finally disappears. From the displacement of these lines from their normal position in a spectrum one can measure the velocities, close to the speed of light, at which these atoms are moving. This, in turn, indicates how fast the black hole itself is rotating. An iron line also tells us how close the accretion disk is reaching to the very edge of the black hole. A new black hole? "All but one of these nine sources had already been identified by ROSAT. Whether they are unobscured sources with straight power-law profiles, or objects whose X-rays are partially absorbed, the XMM-Newton spectra confirm the models -- the way we had imagined we would see these sources in greater detail," explained Guenther Hasinger. "But the bright source -- practically in the center of the image -- is one of XMM-Newton?s new discoveries! "We have given it the number 24021. Its nature is still unclear; it has a very different spectrum, practically no X-rays below the 2 keV energy level and a power-law profile above 2 keV. We haven?t determined its redshift (how far away it is), and to know more we will need to observe this source with the new generation of 8- to 10-meter (315- to 395-inch) telescopes." Those who say spectra are dull must be lacking in imagination. The spectral fingerprints like those shown here are revealing how black holes form and grow. If the Lockman Hole observation is an example, XMM-Newton?s spectrometric mission promises to be extremely rewarding. Next page: detectives of the invisible universe X-Ray Spectra Help Astronomers Hunt Cosmic Monsters (cont.) quinataeesenza: Missing Energy Quintessence (Q) Cosmological Constant (L) W? Quintessence* negative pressure (p) or -1 < w = p/r < 0 time-varying p and r spatially inhomogeneous Caldwell, Dave, PJS. (1998)* Why quintessence? logical possibility that is physically distinct from L excellent fit to current data may solve the ?cosmic coincidence problem? Examples scalar field Q rolling down a potential V(Q) pressure = K.E. - P.E. Slow-roll: K.E. << P.E. or p < 0 W = KE - PE KE + PE Quintessence = equation-of-state Weiss (1987), Ratra & Peebles(1988), Wetterich (1995), Frieman et al (1995), Coble et al (1997), Ferreira & Joyce (1997), Caldwell et al. (1998), ... W can be constant, monotonically increasing or decreasing, or oscillatory Examples web of nonabelian cosmic strings network of nonabelian domain walls W = - 1/3 Quintessence Kamionkowski & Toumbas (1996), Spergel & Pen. (1997), Bucher & Spergel (1998), W = - 2/3 Summary of Evidence for an Exotic Energy Component (Quintessence or Cosmological Constant) L or Q Sum rule: 1 = Wm + Wk + W? Quintessence vs. Cosmological Constant from Wang,Caldwell, Ostriker & PJS (1999) See also Workshop Talk by Robert Caldwell and Poster by Limin Wang see also Turner, Perlmutter and White (1999) Observational Differences COBE + low red shift tests COBE: COBE norm of the mass power spectrum ns: spectral tilt s8: cluster abundance peculiar velocities SHAPE shape of mass power spectrum on scales > 10 Mpc H+BBN+BF: Hubble parameter + Big Bang Nucleosynthesis + Baryon Fraction Bulk Flow Age Observational Differences Conclusions: Both cosmological constant and quintessence fit current observations well Best hopes for discrimination: - CMB anisotropy - Supernovae - gravitational lens statistics (esp. arcs) Quintessence vs. Cosmological Constant Theoretical Advantages The Quintessential Solution: Tracker Fields & Tracker Solutions Zlatev, Wang, & PJS (1998); PJS, Wang,Zlatev (1999) See also Poster by Ivaylo Zlatev For a wide class of potentials G = V? V/(V? 2) > 5/6 and nearly constant The Quintessential Solution: there are attractor solutions to the equations of motion which lead to cosmic acceleration today nearly independent of initial conditions ! Tracker potential: V(Q) = M4 f(Q/M) The Quintessential Solution: The values of WQ and Wm are determined by M Trackers: New Prediction Wm - w relation More Exotic Possibilities ? Evidence mounting Curvature disfavored but still uncertain at present Near-future cosmological observations may decide the issue Profound implications for cosmology & fundamental physics New Problems (?coincidence?) and perhaps novel solutions (?trackers?) and new predictions (Wm - w relation) web site : http://feynman.princeton.edu/~steinh/pritzker/tsld041.htm web site : http://feynman.princeton.edu/~steinh/pritzker/tsld041.htm \newlabel{G e la costante gravitazionale mp la massa del protone c la velocita della luce il denominatore e' la sezione thomson }