Low mass, low range particles called axions have never been seen, but might explain why some strange mirror reversals in quantum physics don't quite look as they should. Since they'd break down into things we can see, we just might be able to spot them … if they exist. So far, experiments looking out for them have come up empty handed. Rather than being made of a new kind of material, dark matter could simply be ordinary objects that act in extraordinary ways.
Massive astrophysical compact halo objects MACHOS are one candidate - heavy, star-like bodies that just don't glow enough. Therefore, its density perturbations can grow first. The resulting gravitational potential acts as an attractive potential well for ordinary matter collapsing later, speeding up the structure formation process.
If dark matter does not exist, then the next most likely explanation must be general relativity — the prevailing theory of gravity — is incorrect and should be modified. The Bullet Cluster, the result of a recent collision of two galaxy clusters, provides a challenge for modified gravity theories because its apparent center of mass is far displaced from the baryonic center of mass.
Type Ia supernovae can be used as standard candles to measure extragalactic distances, which can in turn be used to measure how fast the universe has expanded in the past. Baryon acoustic oscillations BAO are fluctuations in the density of the visible baryonic matter normal matter of the universe on large scales.
These are predicted to arise in the Lambda-CDM model due to acoustic oscillations in the photon—baryon fluid of the early universe, and can be observed in the cosmic microwave background angular power spectrum. BAOs set up a preferred length scale for baryons. This feature was predicted theoretically in the s and then discovered in , in two large galaxy redshift surveys, the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey.
Large galaxy redshift surveys may be used to make a three-dimensional map of the galaxy distribution. These maps are slightly distorted because distances are estimated from observed redshifts ; the redshift contains a contribution from the galaxy's so-called peculiar velocity in addition to the dominant Hubble expansion term.
On average, superclusters are expanding more slowly than the cosmic mean due to their gravity, while voids are expanding faster than average. In a redshift map, galaxies in front of a supercluster have excess radial velocities towards it and have redshifts slightly higher than their distance would imply, while galaxies behind the supercluster have redshifts slightly low for their distance. This effect causes superclusters to appear squashed in the radial direction, and likewise voids are stretched.
Their angular positions are unaffected. This effect is not detectable for any one structure since the true shape is not known, but can be measured by averaging over many structures. It was predicted quantitatively by Nick Kaiser in , and first decisively measured in by the 2dF Galaxy Redshift Survey.
In astronomical spectroscopy , the Lyman-alpha forest is the sum of the absorption lines arising from the Lyman-alpha transition of neutral hydrogen in the spectra of distant galaxies and quasars. Lyman-alpha forest observations can also constrain cosmological models. There are various hypotheses about what dark matter could consist of, as set out in the table below.
Dark matter can refer to any substance which interacts predominantly via gravity with visible matter e. Hence in principle it need not be composed of a new type of fundamental particle but could, at least in part, be made up of standard baryonic matter, such as protons or neutrons. Baryons protons and neutrons make up ordinary stars and planets. However, baryonic matter also encompasses less common non-primordial black holes , neutron stars , faint old white dwarfs and brown dwarfs , collectively known as massive compact halo objects MACHOs , which can be hard to detect.
Candidates for non-baryonic dark matter are hypothetical particles such as axions , sterile neutrinos , weakly interacting massive particles WIMPs , gravitationally-interacting massive particles GIMPs , supersymmetric particles, or primordial black holes. Unlike baryonic matter, nonbaryonic matter did not contribute to the formation of the elements in the early universe Big Bang nucleosynthesis  and so its presence is revealed only via its gravitational effects, or weak lensing.
In addition, if the particles of which it is composed are supersymmetric, they can undergo annihilation interactions with themselves, possibly resulting in observable by-products such as gamma rays and neutrinos indirect detection. If dark matter is composed of weakly-interacting particles, an obvious question is whether it can form objects equivalent to planets , stars , or black holes.
Historically, the answer has been it cannot,   because of two factors:. In — the idea dense dark matter was composed of primordial black holes , made a comeback  following results of gravitational wave measurements which detected the merger of intermediate mass black holes. It was proposed the intermediate mass black holes causing the detected merger formed in the hot dense early phase of the universe due to denser regions collapsing. A later survey of about a thousand supernovae detected no gravitational lensing events, when about eight would be expected if intermediate mass primordial black holes above a certain mass range accounted for the majority of dark matter.
Tiny black holes are theorized to emit Hawking radiation. However the detected fluxes were too low and did not have the expected energy spectrum suggesting tiny primordial black holes are not widespread enough to account for dark matter. In , the lack of microlensing effects in the observation of Andromeda suggests tiny black holes do not exist.
However, there still exists a largely unconstrained mass range smaller than that can be limited by optical microlensing observations, where primordial black holes may account for all dark matter.
Dark matter can be divided into cold , warm , and hot categories. Primordial density fluctuations smaller than this length get washed out as particles spread from overdense to underdense regions, while larger fluctuations are unaffected; therefore this length sets a minimum scale for later structure formation. The categories are set with respect to the size of a protogalaxy an object that later evolves into a dwarf galaxy : Dark matter particles are classified as cold, warm, or hot according to their FSL; much smaller cold , similar to warm , or much larger hot than a protogalaxy.
Cold dark matter leads to a bottom-up formation of structure with galaxies forming first and galaxy clusters at a latter stage, while hot dark matter would result in a top-down formation scenario with large matter aggregations forming early, later fragmenting into separate galaxies; [ clarification needed ] the latter is excluded by high-redshift galaxy observations.
These categories also correspond to fluctuation spectrum effects and the interval following the Big Bang at which each type became non-relativistic. Davis et al. Candidate particles can be grouped into three categories on the basis of their effect on the fluctuation spectrum Bond et al. If the dark matter is composed of abundant light particles which remain relativistic until shortly before recombination, then it may be termed "hot". The best candidate for hot dark matter is a neutrino Such particles are termed "warm dark matter", because they have lower thermal velocities than massive neutrinos Any particles which became nonrelativistic very early, and so were able to diffuse a negligible distance, are termed "cold" dark matter CDM.
There are many candidates for CDM including supersymmetric particles. The 2. Conversely, much lighter particles, such as neutrinos with masses of only a few eV, have FSLs much larger than a protogalaxy, thus qualifying them as hot. Cold dark matter offers the simplest explanation for most cosmological observations. It is dark matter composed of constituents with an FSL much smaller than a protogalaxy.
This is the focus for dark matter research, as hot dark matter does not seem capable of supporting galaxy or galaxy cluster formation, and most particle candidates slowed early. The constituents of cold dark matter are unknown. Studies of Big Bang nucleosynthesis and gravitational lensing convinced most cosmologists       that MACHOs   cannot make up more than a small fraction of dark matter. Peter: " Warm dark matter comprises particles with an FSL comparable to the size of a protogalaxy.
Predictions based on warm dark matter are similar to those for cold dark matter on large scales, but with less small-scale density perturbations. This reduces the predicted abundance of dwarf galaxies and may lead to lower density of dark matter in the central parts of large galaxies. Some researchers consider this a better fit to observations. No known particles can be categorized as warm dark matter. A postulated candidate is the sterile neutrino : A heavier, slower form of neutrino that does not interact through the weak force , unlike other neutrinos.
Some modified gravity theories, such as scalar—tensor—vector gravity , require "warm" dark matter to make their equations work. Hot dark matter consists of particles whose FSL is much larger than the size of a protogalaxy.
The neutrino qualifies as such particle. They were discovered independently, long before the hunt for dark matter: they were postulated in , and detected in Neutrinos interact with normal matter only via gravity and the weak force , making them difficult to detect the weak force only works over a small distance, thus a neutrino triggers a weak force event only if it hits a nucleus head-on.
The three known flavours of neutrinos are the electron , muon , and tau. Their masses are slightly different. Neutrinos oscillate among the flavours as they move.
It is hard to determine an exact upper bound on the collective average mass of the three neutrinos or for any of the three individually. CMB data and other methods indicate that their average mass probably does not exceed 0. Thus, observed neutrinos cannot explain dark matter. Because galaxy-size density fluctuations get washed out by free-streaming, hot dark matter implies the first objects that can form are huge supercluster -size pancakes, which then fragment into galaxies.
Deep-field observations show instead that galaxies formed first, followed by clusters and superclusters as galaxies clump together. If dark matter is made up of sub-atomic particles, then millions, possibly billions, of such particles must pass through every square centimeter of the Earth each second.
Another candidate is heavy hidden sector particles which only interact with ordinary matter via gravity. These experiments can be divided into two classes: direct detection experiments, which search for the scattering of dark matter particles off atomic nuclei within a detector; and indirect detection, which look for the products of dark matter particle annihilations or decays.
Direct detection experiments aim to observe low-energy recoils typically a few keVs of nuclei induced by interactions with particles of dark matter, which in theory are passing through the Earth. After such a recoil the nucleus will emit energy in the form of scintillation light or phonons , as they pass through sensitive detection apparatus.
To do this effectively, it is crucial to maintain a low background, and so such experiments operate deep underground to reduce the interference from cosmic rays. These experiments mostly use either cryogenic or noble liquid detector technologies.
Noble liquid detectors detect scintillation produced by a particle collision in liquid xenon or argon. Both of these techniques focus strongly on their ability to distinguish background particles which predominantly scatter off electrons from dark matter particles that scatter off nuclei.
Currently there has been no well-established claim of dark matter detection from a direct detection experiment, leading instead to strong upper limits on the mass and interaction cross section with nucleons of such dark matter particles. This results from the expectation that as the Earth orbits the Sun, the velocity of the detector relative to the dark matter halo will vary by a small amount.
A special case of direct detection experiments covers those with directional sensitivity. This is a search strategy based on the motion of the Solar System around the Galactic Center. WIMPs coming from the direction in which the Sun travels approximately towards Cygnus may then be separated from background, which should be isotropic.
Indirect detection experiments search for the products of the self-annihilation or decay of dark matter particles in outer space. For example, in regions of high dark matter density e. These processes could be detected indirectly through an excess of gamma rays, antiprotons or positrons emanating from high density regions in our galaxy or others.
A few of the dark matter particles passing through the Sun or Earth may scatter off atoms and lose energy. This could produce a distinctive signal in the form of high-energy neutrinos. Many experimental searches have been undertaken to look for such emission from dark matter annihilation or decay, examples of which follow. The Energetic Gamma Ray Experiment Telescope observed more gamma rays in than expected from the Milky Way , but scientists concluded this was most likely due to incorrect estimation of the telescope's sensitivity.
The Fermi Gamma-ray Space Telescope is searching for similar gamma rays. At higher energies, ground-based gamma-ray telescopes have set limits on the annihilation of dark matter in dwarf spheroidal galaxies  and in clusters of galaxies. They could be from dark matter annihilation or from pulsars. No excess antiprotons were observed. She then feels uneasy and tells Accelerator that he has to dirty his hands to give the dead a clean end.
She references what Kakine said again, and says that only the living can act based on their feelings for the dead, and rejecting that and running way is neither being honest or pacifistic, but plain cowardice.
And with that, Accelerator is released from his stupor and tells her that he will destroy, that he will be the remnant to prove that those people he killed really existed. Kakine finally reacts after listening to them, and asks if they will stop thinking how the dead feel and stop thinking about it.
Mugino tells him that he will never understand, for he is someone who puts words in the dead's mouth for his own benefit and runs away from his feelings regarding the dead himself.
She tells him that he is pathetic even though he is powerful, and would've been better if had remained dead for he would've been merely the esper that defeated her. Then, she tells him the reason she was in there with them. On how someone who pretended to be Frenda attacked her last night, and suspects him for it for he was the biggest factor from the dark side of Academy City active at that time and the interest in playing with the dead was the same.
She tells him that she doesn't know what his purpose was with what he did, and tells him that she will make him pay for disturbing her grave. And with that, their battle begins. Mugino used her beam on Accelerator for his use, redirecting it to all the false clones Kakine created at once, destroying them. Accelerator directs his attention towards Kakine, and uses his vector powers to destroy all the Dark Matter spears he created.
As he twitched, Mugino fired at him, obliterating the top half of his body and most of his legs. However, Kakine appears upon a wall, saying that he can recreate himself. Mugino asks if he moved his flesh and blood organs into the floor before her attack. Kakine redirects the question, and hints many possibilities now that he can replace and create practically anything with his power.
Accelerator does not care however, ripping apart the countless spears and redirected the signals in the center point in the puddle, but to no avail, as Kakine states the network of his Dark Matter expands and information sent faster without direct wiring than he can destroy it.
Despite this, Accelerator continues to try and destroy his Dark Matter, as Mugino continued to assist him, Kakine then asks how much battery time Accelerator has left, and is curious about the wings that no theory can explain.
Kakine just brags on how time is running out, and that he has no problem taking down Mugino. They continued attacking destroying his head, but it is of no avail, as he tells them that he simply has an infinite supply of Dark Matter, and his inspiration is boundless, telling them that to reach him, they need to climb over the wall of infinity that continues on eternally.
He then shoots out countless Dark Matter spears towards them. Kakine continues his assault, but time is running out, and Kakine simply taunts them as his Dark Matter attacks continue to shoot out. But then, something happened; he stopped. Mugino becomes curious, threatening to kill him. But Kakine does not answer, as he too is confused.
He then asks what Accelerator did, believing him to be the culprit. Then, Accelerator realizes something. He tells Kakine that this was the effect of him being "infinite," and tells Kakine that it wasn't him. He did not know, but Beetle 05, the rogue beetle that Kakine ignored, was beginning to take over. As the system begins to transfer authority to Beetle 05, Kakine begins to crack, who cries on how it is not possible for a power that he brought betray him.
Accelerator then tells Kakine that it is no longer matters who was the first Kakine, as he obtained in infinite. Mugino too began to understand. She laughs at his problem of being too powerful, saying that when a network made up of flexibly replaceable equipment has a portion become isolated from the rest, the isolated portion becomes a small network of its own.
Accelerator concludes that the one who stopped Kakine Teitoku was now the Kakine Teitoku. Accelerator is impressed on Dark Matter's capabilities, and mocks him for being unable to wield it. Mugino however notes that he might not be the core Kakine as he had scattered his mind over the system, and the one before them was closest to the surface, though it says of nothing that what showed itself in the surface was the true nature of Kakine Teitoku.
Mugino then asks if they were just battling the outer layer of his mind, and tells that it wasn't easy doing it. Here, she is impressed by Kakine Teitoku, being not a normal person, but not the one before her right now. Slowly, despair overtakes Kakine and slowly more cracks form. Accelerator comments on how there will probably nothing left to prove that he was here, and even if a massive amount of data is left concerning Kakine Teitoku, it will not refer to him.
In his darkest hour, Kakine recalls Takitsubo Rikou being part of the group when he attacked them for the first time. A person he deemed to have been capable of becoming the eighth Level 5. There, Kakine realized that she might be the one, consciously or subconsciously, that have incited the change in Beetle Kakine is enraged greatly.
He shouts his fury in that underground passageway with only Accelerator and Mugino as his audience. Accelerator however, had enough, and pierced his center of the thing before them, completely shattering it, and the Dark Matter dissolved into the air, leaving nothing behind. Mugino Shizuri is actually right in her assessment, as Kakine Teitoku's true flesh and blood organs have been kept in secret, and has somehow come into the possession of Ollerus.
Kakine Teitoku's original personality is revived by Gremlin at Tokyo Bay, who wishes to use his Dark Matter to create the magic spear Gungnir.
When Kakine has regained consciousness, he tries to mock the members of Gremlin about how foolish it was to revive and use him for their own purposes. This results in Kakine immediately trying to kill the members of Gremlin. However Kakine is stopped by Othinus, who lifts Kakine and holds him painfully by the neck. After Kakine realizes that he is disabled by Othinus, he declares his submission to the Magic God.
Afterwards his dark matter body is turned into a ball-like shape by Othinus, which is given to the members of Gremlin to use for the completion of Gungnir. He refuses, but the agent insists, earning a lashing from Kakine.
The agent then suggests that Kakine's power, more specifically, his white wings, would have appeal among kids. The Boy with goggles and Girl in the dress are amused, but are quickly silenced by Kakine's furious glare. Kihara Yuiitsu , who has studied Accelerator and Kakine, compares the two with the duality of Destruction and Production.
It should be noted that the term "Dark Matter" is not to be confused with the true "Dark Matter" which is among the components of the universe. In addition, 'unknown matter' here does not mean matter that has not been discovered by humans but matter that did not exist until it was created by Kakine. The material he creates defies the Laws of Physics, allowing him to produce 25, different types of energy.
The most obvious of this is the six angelic wings, which grants him the power to fly, blow powerful gusts of wind that is affected by Dark Matter, and have sunlight pass diffract upon it to form harmful rays of light.
His ability also appears to grant him a form of super strength, though he is still not strong enough to overpower Accelerator with sheer brute force. During Kakine's brief conflict with the DA and Kihara Souji , he displayed much more varied abilities and capabilities of his Dark Matter, as seen when he managed to twist a DA's agents arm into mince meat and disintegrate his other arm into smoke simultaneously.
Before being torn apart by Accelerator, an "unprecedented power" expanded within Kakine, apparently mastering his Dark Matter and believed that he could easily defeat Accelerator with it. The Western fandom term Awakening is taken from a personification of Kakine's wings during this scene, describing it as "awakened". After his revival, it was revealed that he can now seemingly infinitely create a variety of objects using Dark Matter, even organs.
Kakine reveals himself to be able to create a body made out of pure Dark Matter, making him white in the process. In this seemingly infinite supply of Dark Matter, Kakine can apparently survive so long as there is Dark Matter.
He can create autonomous beings such as a copy of his own body, bodies of other people, and cyborg-like beings like the White Beetles and dragonfly. There is a sort of "network" to his creations, where he has some form of control over them and allowing them regenerate their Dark Matter when they are injured. One of the queer powers that Kakine has learned is the ability to run his Dark Matter in an area's surface, to obtain information of past events, like a powerful form of Psychometry.
Moreover, through the use of Dark Matter, he can give them shape. It is like a CD where individual tracks refer to each unique information gathered. With this simile, it would be like he can allow the shape to "play" the track that was gathered by him. Originally, his brain, that he somehow left behind and did not carry with him, produced Dark Matter through his Personal Reality.
However due to the fact that he has essentially made himself immortal and infinite through the use of Dark Matter, allowing other parts to be referred to as Kakine Teitoku, there was no longer an issue for whomever the brain referred to.
This would normally not be a problem, since Kakine seems to still have no ability to create things with Personal Reality, a being with will of their own, and to forcibly let them refer to themself as Kakine.
However, when Beetle 05, came into contact with Rikou and her AIM Stalker , an esper power that is predicted to manipulate Personal Realities, Beetle 05 became isolated from Kakine's network.
When a network made up of flexibly replaceable equipment, like Kakine's "network", has a portion become isolated from the rest, the isolated portion becomes a small network of its own. As such, it also becomes referred to as a "Kakine Teitoku," and if so chooses, can take over the entire network, and be referred to as the Kakine Teitoku.
Haimura Kiyotaka designed Kakine around the idea of a backup yakuza member and a host in a host club, giving him a look like someone approachable but would immediately turn to someone that would threaten you, opposite to Accelerator, who has an aura of danger around him.
His design for his return form is the same as his original design apart from his body being made of black and white colors.
Sign In Don't have an account? Start a Wiki. Series Three Overhaul Project This article will be undergoing extensive revision as part of wiki overhaul sub-plan Operation Interim This article deals with the original Kakine Teitoku. Contents [ show ]. The wings produced from Dark Matter Wings allowing flight A powerful gust of wind Deflecting and aiming the sunlight into a concentrated deadly ray Manipulate air pressure in specific area Turning cells into sand.
Character design, head detail, and Kakine with his Dark Matter wings, along with the Tweezers, as designed for the 15th Toaru Majutsu no Index light novel, by Haimura Kiyotaka. The reality of this missing mass remained in question for decades, until the s when American astronomers Vera Rubin and W. In general, the speed with which stars orbit the centre of their galaxy is independent of their separation from the centre; indeed, orbital velocity is either constant or increases slightly with distance rather than dropping off as expected.
The presence of this missing matter in the centres of galaxies and clusters of galaxies has also been inferred from the motion and heat of gas that gives rise to observed X-rays. For example, the Chandra X-ray Observatory has observed in the Bullet cluster , which consists of two merging galaxy clusters, that the hot gas ordinary visible matter is slowed by the drag effect of one cluster passing through the other.
The mass of the clusters, however, is not affected, indicating that most of the mass consists of dark matter.
Matter is Only 0. The rest is dark matter. Two varieties of dark matter have been found to exist. The first variety is about 4. Most of this baryonic dark matter is expected to exist in the form of gas in and between the galaxies.
This baryonic, or ordinary, component of dark matter has been determined by measuring the abundance of elements heavier than hydrogen that were created in the first few minutes after the big bang occurredJun 17, · Speaker: Tracy Slatyer (MIT) Summer School on Particle Physics | (smr ) _06__smrmp4.