Showing posts with label dark matter. Show all posts
Showing posts with label dark matter. Show all posts

Tuesday, December 20, 2016

Search for Dark Matter in Gamma Rays

This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun. Credit: NASA/DOE/Fermi LAT Collaboration

The all-sky image released today shows us how the cosmos would look if our eyes could detect radiation 150 million times more energetic than visible light. The view merges LAT observations spanning 87 days, from August 4 to October 30, 2008. See:
Fermi's Best-Ever Look at the Gamma-Ray Sky

Wednesday, December 07, 2016

Dark Matter Not So Rough Around the Edges

Analysis of a giant new galaxy survey, made with ESO’s VLT Survey Telescope in Chile, suggests that dark matter may be less dense and more smoothly distributed throughout space than previously thought. An international team used data from the Kilo Degree Survey (KiDS) to study how the light from about 15 million distant galaxies was affected by the gravitational influence of matter on the largest scales in the Universe. The results appear to be in disagreement with earlier results from the Planck satellite. Credit: Kilo-Degree Survey Collaboration/H. Hildebrandt & B. Giblin/ESO
Hendrik Hildebrandt from the Argelander-Institut für Astronomie in Bonn, Germany and Massimo Viola from the Leiden Observatory in the Netherlands led a team of astronomers [1] from institutions around the world who processed images from the Kilo Degree Survey (KiDS), which was made with ESO’s VLT Survey Telescope (VST) in Chile. For their analysis, they used images from the survey that covered five patches of the sky covering a total area of around 2200 times the size of the full Moon [2], and containing around 15 million galaxies. See:  Dark Matter May be Smoother than Expected


Sunday, November 13, 2016

Dark Matter and Dark Energy Information

The importance of the CMB, while a snapshot of the early universe just after 380000 years after the big bang is a materialist point of view, other things were born, as with the idea about the current state of the universe. What is dominating in terms of dark energy.


Talking About Dark Matter and Dark Energy

So here is one I did this morning, about why cosmologists think dark matter and dark energy are things that really exist
See also:


Emergent Gravity and the Dark Universe by Erik P. Verlinde

Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional `dark' gravitational force describing the `elastic' response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton's constant and the Hubble acceleration scale a_0 =cH_0, and provide evidence for the fact that this additional `dark gravity~force' explains the observed phenomena in galaxies and clusters currently attributed to dark matter.

Friday, February 06, 2015

Dark Matter Research

An overview of how the LHC at CERN can look for dark matter. (Credit: STFC/Ben Gilliland)
(Click on Image for larger viewing)


See Also:

Thursday, October 24, 2013

(HD) Dark Matter & Dark Energy in the Universe - Full Documentary

See:(HD) Dark Matter & Dark Energy in the Universe - Full Documentary

The Xenon Dark Matter Project

Model of the Cryogenic Dark Matter Search which translates actual data into sound and light. We have not yet had a dark matter interaction, but we have lots of particles hitting the detectors and that is what you are watching. A downloadable version is at my webpage More info on our experiment can be found at and

There is current data that deals with this topic that has been transformed in how we look at this issue.  I leave that up to viewers to think about all the other bloggers that have already spoken to this. I wll give one link below for consideration.


Wednesday, April 24, 2013


Pictorial image showing, superimposed to an optical image, the spatial distributions of ordinary matter (pink) and the one assigned to dark matter (blue) estimated studying the merging of two clusters of galaxies (Bullet Cluster)

The DarkSide collaboration is an international affiliation of universities and labs seeking to directly detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). The collaboration is building a series of noble liquid time projection chambers (TPCs) that are designed to be employed at the Gran Sasso National Laboratory in Assergi, Italy. The technique is based on liquid argon depleted in radioactive isotope 39Ar which is common for the atmospheric argon.

Dark-matter seekers get help from the DarkSide


As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototype detector with an active volume containing 10 kg of liquid argon, DarkSide-10, was built and operated underground in the Gran Sasso National Laboratory in Italy. A critically important parameter for such devices is the scintillation light yield, as photon statistics limits the rejection of electron-recoil backgrounds by pulse shape discrimination. We have measured the light yield of DarkSide-10 using the readily-identifiable full-absorption peaks from gamma ray sources combined with single-photoelectron calibrations using low-occupancy laser pulses. For gamma lines of energies in the range 122-1275 keV, we get consistent light yields averaging 8.887\pm0.003(stat)\pm0.444(sys) p.e./keV_ee. With additional purification, the light yield measured at 511 keV increased to 9.142\pm0.006(stat) p.e./keV_ee. See:
Light Yield in DarkSide-10: a Prototype Two-phase Liquid Argon TPC for Dark Matter Searches

Saturday, March 30, 2013

Recent results from the AMS experiment by Prof. Samuel Ting (Massachusetts Inst. of Technology (US))

Wednesday, April 3, 2013 from 17:00 to 18:00 (Europe/Zurich) at CERN ( 500-1-001 - Main Auditorium )

 Cern Webcast

See Also:

Thank you Lubos Motl for the Update.

Sunday, July 15, 2012

Thoughts On Dark Matter Search


A filament of dark matter has been directly detected between the galaxy clusters Abell 222 and Abell 223. The blue shading and yellow contour lines represent the density of matter. Image credit: Jörg Dietrich, U-M Department of Physics

In light of direction LHC is experiencing there is always the questions of Oversight in terms of the direction science needs to take. I have listed one aspect of the question of directions that may be of interest here? I have seen this procedure used over and over again. This is how I know to focus in on the experiments as they are listed and work backwards to gain full insight in these experimental procedures.

 This focus with regard to be "lead by science is part of the mantra" I hold and features part of my respect toward the science process that I have come to build in respect of where we are going and what is happening. In this spirit there has always been help by scientists who want to help the lay public with information to help exceed current levels of understanding with regard to where we are right now in that science.

 The challenge is not to be lost in the confrontations of opposing view points in science but to focus more on what is being offered in terms of advancing that science knowledge. One has to put aside these character attacks in order to focus on the science process itself and information. Character attacks on theoretical definitions.

 Following scientists you get to know who is respecting this foundational approach in order to push forward public knowledge. The vitriolic statements about character are like sandpaper or a screeching board, to respect for individuals in their pursuits

Over the years as a researcher of sorts digging deeply for the directions science projects are initiated are always with the idea that advisory boards put forward proposals for money toward experimental procedures.

 So in order to justified this money I have to believe the best approach to advancing that money is to consider it as a method to falsify on scientific grounds.

 I know people have their own theories but in order to advance falsifiable methods these have to be considered at the time the phenomenology of experimentation is proposed as part of the development of that method to do so.

 So the OP introduction toward a news article is hardly sufficient to think about the advancement of any theory on the grounds that it could encapsulate the entire process of advancing science as nothing more then news fodder. To be able to raise the question for those who believe that it is a opportunity to advance their own theories or to ask the question in the spirit of the OP?

 Liquid Xenon both scintillates and becomes ionized when hit by particles (i.e. photons, neutrons and potentially dark matter). The ratio of scintillation over ionization energy caused by the collision provides a way of identifying the interacting particle. The leading theoretical dark matter candidate, the Weakly Interacting Massive Particle (WIMP), could be identified in this way. LUX Dark Matter


Wednesday, July 11, 2012

Fermi Provides Insights?

 There's more to the cosmos than meets the eye. About 80 percent of the matter in the universe is invisible to telescopes, yet its gravitational influence is manifest in the orbital speeds of stars around galaxies and in the motions of clusters of galaxies. Yet, despite decades of effort, no one knows what this "dark matter" really is. Many scientists think it's likely that the mystery will be solved with the discovery of new kinds of subatomic particles, types necessarily different from those composing atoms of the ordinary matter all around us. The search to detect and identify these particles is underway in experiments both around the globe and above it.
Scientists working with data from NASA's Fermi Gamma-ray Space Telescope have looked for signals from some of these hypothetical particles by zeroing in on 10 small, faint galaxies that orbit our own. Although no signals have been detected, a novel analysis technique applied to two years of data from the observatory's Large Area Telescope (LAT) has essentially eliminated these particle candidates for the first time. See: Fermi Observations of Dwarf Galaxies Provide New Insights on Dark Matter 04.02.12

NGC 147, a dwarf spheroidal galaxy of the Local Group
Dwarf spheroidal galaxy (dSph) is a term in astronomy applied to low luminosity galaxies that are companions to the Milky Way and to the similar systems that are companions to the Andromeda Galaxy M31. While similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust or recent star formation, they are approximately spheroidal in shape, generally lower luminosity, and are only recognized as satellite galaxies in the Local Group.[1]

While there were nine "classical" dSph galaxies discovered up until 2005, the Sloan Digital Sky Survey has resulted in the discovery of 11 more dSph galaxies—this has radically changed the understanding of these galaxies by providing a much larger sample to study.[2]

Recently, as growing evidence has indicated that the vast majority of dwarf ellipticals have properties that are not at all similar to elliptical galaxies, but are closer to irregular and late-type spiral galaxies, this term has been used to refer to all of the galaxies that share the properties of those above. These sorts of galaxies may in fact be the most common type of galaxies in the universe, but are much harder to see than other types of galaxies because they are so faint.

Because of the faintness of the lowest luminosity dwarf spheroidals and the nature of the stars contained within them, some astronomers suggest that dwarf spheroidals and globular clusters may not be clearly separate and distinct types of objects.[3] Other recent studies, however, have found a distinction in that the total amount of mass inferred from the motions of stars in dwarf spheroidals is many times that which can be accounted for by the mass of the stars themselves. In the current predominantly accepted \Lambda Cold Dark Matter cosmology, this is seen as a sure sign of dark matter, and the presence of dark matter is often cited as a reason to classify dwarf spheroidals as a different class of object from globular clusters (which show little to no signs of dark matter). Because of the extremely large amounts of dark matter in these objects, they may deserve the title "most dark matter-dominated galaxies" [4]

See also


External links



  1. ^ Mashchenko, Sergey; Sills, Alison; Couchman, H. M. (March 2006), "Constraining Global Properties of the Draco Dwarf Spheroidal Galaxy", The Astrophysical Journal 640 (1): 252–269, arXiv:astro-ph/0511567, Bibcode 2006ApJ...640..252M, DOI:10.1086/499940
  2. ^ Simon, Josh; Geha, Marla (November 2007), "The Kinematics of the Ultra-faint Milky Way Satellites: Solving the Missing Satellite Problem", The Astrophysical Journal 670 (1): 313–331, Bibcode 2007ApJ...670..313S, DOI:10.1086/521816
  3. ^ van den Bergh, Sidney (November 2007), "Globular Clusters and Dwarf Spheroidal Galaxies", MNRAS (Letters), in press 385 (1): L20, arXiv:0711.4795, Bibcode 2008MNRAS.385L..20V, DOI:10.1111/j.1745-3933.2008.00424.x
  4. ^ Strigari, Louie; Koushiappas, et al; Bullock, James S.; Kaplinghat, Manoj; Simon, Joshua D.; Geha, Marla; Willman, Beth (September 2007), "The Most Dark Matter Dominated Galaxies: Predicted Gamma-ray Signals from the Faintest Milky Way Dwarfs", The Astrophysical Journal 678 (2): 614, arXiv:0709.1510, Bibcode 2008ApJ...678..614S, DOI:10.1086/529488

See Also:

Wednesday, April 25, 2012

Do Gamma rays hint at dark matter?

Using a new statistical technique to analyse publicly available data from NASA's Fermi Space Telescope, an astrophysicist in Germany says he may have spotted a tell-tale sign of exotic particles annihilating within the Milky Way. If proved to be real, this "gamma-ray line" would, he claims, be a "smoking-gun signature" of dark matter.

There is a wide body of indirect observational evidence that an invisible substance accounts for some 80% of the matter in the universe. Although physicists can measure the effects that this dark matter has on the visible universe, they have very little understanding of what this mysterious stuff actually is. As well as looking for direct evidence of dark matter by detecting it – or even producing it – here on Earth, researchers are also scouring the skies for signs of the particles that dark matter might produce when self-annihilating. An excess of high-energy positrons (anti-electrons) observed by the Italian-led PAMELA spacecraft in 2008, and confirmed by Fermi last year, might be such a signature. However, it is possible that these positrons are produced by processes unrelated to dark matter. See:Gamma rays hint at dark matter
Also a Physics World see: Has Fermi glimpsed dark matter?

Wednesday, December 07, 2011

Gordon Kane Post on Reference Frame

Fig.3 Revisionist History and String Theory and the Real World
See: "Learning from theory and data about our string vacuum"


Also for viewing:

NAS Produces Animations of Dark Matter for Planetarium Shows

The newly-installed Alpha Magnetic Spectrometer-2 (AMS)


Excerpt from "Alpha Magnetic Spectrometer - A Physics Experiment on the International Space Station" by Dr. Sam Ting: The Alpha Magnetic Spectrometer (AMS-02) is a state-of-the-art particle physics detector constructed, tested and operated by an international team composed of 60 institutes from 16 countries and organized under United States Department of Energy (DOE) sponsorship. The AMS-02 will use the unique environment of space to advance knowledge of the universe and lead to the understanding of the universe's origin by searching for antimatter, dark matter and measuring cosmic rays.

Experimental evidence indicates that our Galaxy is made of matter; however, there are more than 100 hundred million galaxies in the universe and the Big Bang theory of the origin of the universe requires equal amounts of matter and antimatter. Theories that explain this apparent asymmetry violate other measurements. Whether or not there is significant antimatter is one of the fundamental questions of the origin and nature of the universe. Any observations of an antihelium nucleus would provide evidence for the existence of antimatter. In 1999, AMS-01 established a new upper limit of 10-6 for the antihelium/helium flux ratio in the universe. AMS-02 will search with a sensitivity of 10-9, an improvement of three orders of magnitude, sufficient to reach the edge of the expanding universe and resolve the issue definitively.

The visible matter in the universe (stars) adds up to less than 5 percent of the total mass that is known to exist from many other observations. The other 95 percent is dark, either dark matter (which is estimated at 20 percent of the universe by weight or dark energy, which makes up the balance). The exact nature of both still is unknown. One of the leading candidates for dark matter is the neutralino. If neutralinos exist, they should be colliding with each other and giving off an excess of charged particles that can be detected by AMS-02. Any peaks in the background positron, anti-proton, or gamma flux could signal the presence of neutralinos or other dark matter candidates.

Six types of quark (u, d, s, c, b and t) have been found experimentally, however all matter on Earth is made up of only two types of quarks (u and d). It is a fundamental question whether there is matter made up of three quarks (u, d and s). This matter is known as Strangelets. Strangelets can have extremely large mass and very small charge-to-mass ratios. It would be a totally new form of matter. AMS will provide a definitive answer on the existence of this extraordinary matter. The above three examples indicates that AMS will probe the foundations of modern physics.

Cosmic radiation is a significant obstacle to a manned space flight to Mars. Accurate measurements of the cosmic ray environment are needed to plan appropriate countermeasures. Most cosmic ray studies are done by balloon-borne satellites with flight times that are measured in days; these studies have shown significant variations. AMS-02 will be operative on the ISS for a nominal mission of 3 years, gathering an immense amount of accurate data and allowing measurements of the long term variation of the cosmic ray flux over a wide energy range, for nuclei from protons to iron. After the nominal mission, AMS-02 can continue to provide cosmic ray measurements. In addition to the understanding the radiation protection required for manned interplanetary flight, this data will allow the interstellar propagation and origins of cosmic rays to be pinned down. See:
The newly-installed Alpha Magnetic Spectrometer-2 (AMS)

Apex Experiment

APEX is one of several experiments hunting for the carrier of a new force, a hypothetical boson dubbed A’. This graph shows the range of the parameter space covered by these proposed experiments. The solid red is the slice of parameter space covered by APEX’s test run. The full APEX experiment will search the entire area above the red curve. See: PI Science: Hunting for New Forces
We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling $\alpha'$ to electrons. Such a particle $A'$ can be produced in electron-nucleus fixed-target scattering and then decay to an $e^+e^-$ pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an $A'\to e^+e^-$ reaction, and set an upper limit of $\alpha'/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces. See: Search for a new gauge boson in the $A'$ Experiment (APEX)


Rouven Essig, Search for a New Vector Boson Decaying to e+e- (talk to Hall A Collaboration on APEX Motivation ).

Wednesday, November 09, 2011

A Mysterious Dark Flow?

Dark flow is an astrophysical term describing a peculiar velocity of galaxy clusters. The actual measured velocity is the sum of the velocity predicted by Hubble's Law plus a small and unexplained (or dark) velocity flowing in a common direction.

According to standard cosmological models, the motion of galaxy clusters with respect to the cosmic microwave background should be randomly distributed in all directions. However, analyzing the three-year WMAP data using the kinematic Sunyaev-Zel'dovich effect, the authors of the study found evidence of a "surprisingly coherent" 600–1000 km/s[1] flow of clusters toward a 20-degree patch of sky between the constellations of Centaurus and Vela.

The authors, Alexander Kashlinsky, F. Atrio-Barandela, D. Kocevski and H. Ebeling, suggest that the motion may be a remnant of the influence of no-longer-visible regions of the universe prior to inflation. Telescopes cannot see events earlier than about 380,000 years after the Big Bang, when the universe became transparent (the Cosmic Microwave Background); this corresponds to the particle horizon at a distance of about 46 billion (4.6×1010) light years. Since the matter causing the net motion in this proposal is outside this range, it would in a certain sense be outside our visible universe; however, it would still be in our past light cone.

The results appeared in the October 20, 2008, issue of Astrophysical Journal Letters.[1][2][3] Since then, the authors have extended their analysis to additional clusters and the recently released WMAP five-year data.


This all-sky view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way and has been desaturated to serve as the background for the dark flow plots. The image is derived from the 2MASS Extended Source Catalog, which contains more than 1.5 million galaxies, and the Point Source Catalog, which holds nearly 500 million stars within the Milky Way. The galaxies are color coded for distances obtained by various surveys. The nearest sources are blue (redshifts less than 0.01), moderately distant sources (redshifts between 0.01 and 0.04) are green, and red represents the farthest sources that 2MASS resolves (between redshifts of 0.04 and 0.1).(click image for larger viewing)

Video showing direction of travel of galaxy clusters at four distances from Earth. The colored dots are clusters within one of four distance ranges, with redder colors indicating greater distance. Colored ellipses show the axis of bulk motion for clusters of the corresponding color. Images of representative galaxy clusters in each distance slice are also shown. Credit: NASA/GSFC/A. Kashlinsky et al.

Distant galaxy clusters mysteriously stream at a million miles per hour along a path roughly centered on the southern constellations Centaurus and Hydra. A new study led by Alexander Kashlinsky at NASA's Goddard Space Flight Center in Greenbelt, Md., tracks this collective motion -- dubbed the "dark flow" -- to twice the distance originally reported, out to more than 2.5 billion light-years.

The study used a new technique to determine the motion of X-ray-emitting galaxy clusters. The clusters appear to be moving along a line extending from our solar system toward Centaurus/Hydra, but the direction of this motion is less certain. Evidence indicates that the clusters are headed outward along this path, away from Earth, but the team cannot yet rule out the opposite flow.

The video shows the team's catalog of galaxy clusters separated into four "slices" representing different distance ranges. A colored ellipse shows the flow axis for the clusters within each slice. While the size and exact position of the ellipses vary, the overall trends show remarkable agreement. The video includes images of representative clusters in each distance slice.

The dark flow is controversial because the distribution of matter in the observed universe cannot account for it. Its existence suggests that some structure beyond the visible universe -- outside our "horizon" -- is pulling on matter in our vicinity. See: Dark Flow

See Also: Dark Energy, Dark Flow, and can  we explain it away?

Tuesday, October 18, 2011

The Chicagoland Observatory for Underground Particle Physics (COUPP)

The Chicagoland Observatory for Underground Particle Physics (COUPP) collaboration looks for bubbles in chambers filled with a compound containing carbon, fluorine and iodine. The fluid is superheated beyond the boiling point but has no rough surface to form bubbles. When a specific type of particle interacts in the chamber, it can deposit enough energy to boil the fluid and make a bubble. Electrons do not produce bubbles, while a dark matter particle interacting with a nucleus can – making this the key for dark matter detection. See:Bubble chamber gets more precise in dark matter search

Bold added for emphasis.

See Also: Bubble chamber gets more precise in dark matter search


The accelerating universe is the observation that the universe appears to be expanding at an increasing rate, which in formal terms means that the cosmic scale factor a(t) has a positive second derivative,[1] implying that the velocity at which a given galaxy is receding from us should be continually increasing over time[2] (here the recession velocity is the same one that appears in Hubble's law; defining 'velocity' in cosmology is somewhat subtle, see Comoving distance#Uses of the proper distance for a discussion). In 1998, observations of type Ia supernovae suggested that the expansion of the universe has been accelerating[3][4] since around redshift of z~0.5.[5] The 2006 Shaw Prize in Astronomy and the 2011 Nobel Prize in Physics were both awarded to Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess for the 1998 discovery of the accelerating expansion of the Universe through observations of distant supernovae.[6][7]


In cosmology, baryon acoustic oscillations (BAO) refers to an overdensity or clustering of baryonic matter at certain length scales due to acoustic waves which propagated in the early universe.[1] In the same way that supernova experiments provide a "standard candle" for astronomical observations,[2] BAO matter clustering provides a "standard ruler" for length scale in cosmology.[1] The length of this standard ruler (~150 Mpc in today's universe[3]) can be measured by looking at the large scale structure of matter using astronomical surveys.[3] BAO measurements help cosmologists understand more about the nature of dark energy (the acceleration of the universe) by constraining cosmological parameters.[1]

SDSS III: 2008-2014

In mid-2008, SDSS-III was started. It comprises four separate surveys, each conducted on the same 2.5m telescope: [9][10]

Baryon Oscillation Spectroscopic Survey (BOSS)

The SDSS-III's Baryon Oscillation Spectroscopic Survey (BOSS) will map the spatial distribution of luminous red galaxies (LRGs) and quasars to detect the characteristic scale imprinted by baryon acoustic oscillations in the early universe. Sound waves that propagate in the early universe, like spreading ripples in a pond, imprint a characteristic scale on the positions of galaxies relative to each other [12] .

See Also:

        Thursday, August 12, 2010

        Dark Matter

        (Click on Image)

        Friedman Equation What is pdensity.

        What are the three models of geometry? k=-1, K=0, k+1

        Negative curvature

        Omega=the actual density to the critical density
        If we triangulate Omega, the universe in which we are in, Omegam(mass)+ Omega(a vacuum), what position geometrically, would our universe hold from the coordinates given?  

        See Also:

        I am not sure if it is proper to take such expressions of dark energy and dark matter as they are perceived in the universe and apply them to a "dynamical movement of a kind,"  as an expression of that Universe?

        Part of that "Toposense" you might say?

        IN their figure 2. Hyperbolic space, and their comparative relation to the M.C.Escher's Circle Limit woodcut, Klebanov and Maldacena write, " but we have replaced Escher's interlocking fish with cows to remind readers of the physics joke about the spherical cow as an idealization of a real one. In anti-de Sitter/conformal theory correspondence, theorists have really found a hyperbolic cow."

        Click on image for larger version. See:Solving quantum field theories via curved spacetimes by Igor R. Klebanov and Juan M. Maldacena


        Thursday, July 29, 2010

        Lighting up the dark universe

        Image ...
        The CHASE detector. The end of the magnet (orange) can be seen on the right.

        Exploring our dark universe is often the domain of extreme physics. Traces of dark matter particles are searched for by huge neutrino telescopes located underwater or under Antarctic ice, by scientists at powerful particle colliders, and deep underground.  Clues to mysterious dark energy will be investigated using big telescopes on Earth and experiments that will be launched into space.
        But an experiment doesn’t have to be exotic to explore the unexplained. At the International Conference on High Energy Physics, which ended today in Paris, scientists unveiled the first results from the GammeV-CHASE experiment, which used 30 hours’ worth of data from a 10-meter-long experiment to place the world’s best limits on the existence of dark energy particles.
        CHASE, which stands for Chameleon Afterglow Search, was constructed at Fermilab to search for hypothetical particles called chameleons. Physicists theorize that these particles may be responsible for the dark energy that is causing the accelerating expansion of our universe.

        “One of the reasons I felt strongly about doing this experiment is that it was a good example of a laboratory experiment to test dark energy models,” says CHASE scientist Jason Steffen, who presented the results at ICHEP. “Astronomical surveys are important as well, but they’re not going to tell us everything.” CHASE was a successor to Fermilab’s GammeV experiment, which searched for chameleon particles and another hypothetical particle called the axion.

        See: Lighting up the dark universe by Katie Yurkewicz Posted in ICHEP 2010

        See Also:Backreaction: Detection of Dark Energy on Earth? - Improbable

        Wednesday, May 26, 2010

        There Be Dragons on the Dark Matter Issue?

         I have been intrigued by the comparison of the latest reporting by Bee of Backreaction at a workshop at Perimeter Institute about the Laws of Nature: Their Nature and Knowability.

        Bee writes, "Yesterday, we had a talk by Marcelo Gleiser titled “What can we know of the world?”."

        I look at this from a historical position as it has been outplayed from the beginning as to the understanding that gravity in the universe can have it's counterpart revealed the action of a phenomenology search for the dark matter constituents while describing the state of the uinverse.
        The type of detective work described by Sherlock Holmes has been used by astronomers for a long time to deepen our understanding of the universe. Ever since the phenomenal success of Isaac Newton in explaining the motion of the planets with his theory of gravity and laws of motion in 1687, unseen matter has been invoked to explain puzzling observations of cosmic bodies.

        For example, the anomalous motion of Uranus led astronomers to suggest that an unseen planet existed, and a few years later, in 1846, Neptune was discovered. This procedure is still the primary method used to discover planets orbiting stars.
        A similar line of reasoning led to the detection in 1862, of the faint white dwarf Sirius B in orbit around the bright star Sirius.

        In contrast, the attempt to explain the anomalies in the motion of Mercury as due to the existence of a new planet, called Vulcan, did not succeed. The solution turned out to be Einstein's theory of general of relativity, which modified Newton's theory.
        Today, astronomers are faced with a similar, though much more severe, problem. Unlike the case of Uranus, where the gravity of Neptune adds a fraction of a percent to the gravitational force acting of Uranus, the extra force needed in the cases described below is several hundred percent! It is no exaggeration to say that solving the dark matter problem will require a profound change in our understanding of the universe. See:Field Guide to Dark Matter

        So given the outlay of experiential work to the subject there would be those that counter the proposal to support such research because they believe that such an exercise if fruitless to solving the nature of the cosmos and the way the universe could be expanding according to some speeding up of a gravitational consideration ?


        Impressions from the PI workshop on the Laws of Nature

        See Also:
        There Be Dragons?
        Map of North America from 1566 showing both Terra In Cognita and Mare In Cognito.
        Sounding Off on the Dark Matter Issue
        Dark Matter Discovery Announced by Nasa

        Monday, December 21, 2009

        Sounding off on Economic Constraints in Experimentation

        I mean most understand that the economic spending "is the choice" as to whether an area of research will be continued to be funded or not, according to the direction that research council choose. Limited resources according to the times? This is not a reflection of the absurdity of going in a certain direction, but one of where the money is to allocated from a scientific endeavor and standpoint.

        Finally, tantalisingly, the Cryogenic Dark Matter Search (CDMS) released the results of its latest (and final) effort to search for the Dark Matter that seems to make up most of the matter in the Universe, but doesn’t seem to be the same stuff as the normal atoms that we’re made of. Under some theories, the dark matter would interact weakly with normal matter, and in such a way that it could possibly be distinguished from all the possible sources of background. These experiments are therefore done deep underground — to shield from cosmic rays which stream through us all the time — and with the cleanest and purest possible materials — to avoid contamination with both both naturally-occurring radioactivity and the man-made kind which has plagued us since the late 1940s.See:Doctors, Deep Fields and Dark Matter (Bold added for emphasis by me)



        Observational studies of the rotation of galaxies and groups of galaxies strongly suggest the existence of a dominating amount of matter invisible at any electromagnetic wavelengths. One of the favoured forms of this "missing mass", both theoretically and observationally, is the WIMP (Weakly Interacting Massive Particle). These cold WIMPs are expected to be scattered by the nuclei of typical detector material at a rate of less than one per kg per day, yielding energy depositions in the 1-50 keV energy range.

        ZEPLIN-III is a two-phase (liquid/gas) xenon detector looking for galactic WIMP dark matter at the Boulby Underground Laboratory, North Yorkshire, UK, at a depth of 1100 m. At this depth the cosmic-ray background is reduced by a factor of a million. The WIMP target consists of 12 kg of cold liquid xenon topped by a thin layer of xenon gas. These are viewed by an array of 31 photomultiplier tubes immersed in the liquid.

        The detector operates at higher electric fields than other, similar systems, namely its predecessor ZEPLIN-II, and provides high-precision reconstruction of the interaction point in three dimensions. Together with the low-background construction (mainly high-purity copper), these features will give ZEPLIN-III higher sensitivity in direct WIMP searches.

        The ZEPLIN-III Collaboration includes the University of Edinburgh, Rutherford Appleton Laboratory, Imperial College London, LIP-Coimbra (Portugal) and ITEP-Moscow (Russia).


        Photomultiplier array covered by electrode grid