"Gravitinos" --Will They Unlock the Mystery of Dark Matter in the Universe?
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January 23, 2013

"Gravitinos" --Will They Unlock the Mystery of Dark Matter in the Universe?

 

 

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Astrophysicists have known for the last 80 years that most of the universe consists of an unknown, dark matter. The solution to the mystery may now be just around the corner. "We are looking for a new member of our particle zoo in order to explain dark matter. We know that it is a very exotic beast. And we have found a plausible explanation," reports Are Raklev, an associate professor in particle physics in the University of Oslo's Department of Physics --the university's leading theorist in astroparticle physics. Raklev has launched a model that explains what dark matter may consist of and how one can discover the invisible particles experimentally.

Even though dark matter is invisible, astrophysicists know it exists. Without this dark matter it is impossible to explain how the visible things in the universe hang together. An 80 year fight The world famous, Swiss physicist Fritz Zwicky was speculating on what dark matter might be as early as the 1930s. Astrophysicists have calculated that 80 per cent of all the mass in the universe is dark, invisible matter. Thanks to gravity this dark matter clumps together as ordinary matter. Dark matter can explain why stars move like they do. Dark matter may also explain the rotation speed of galaxies.

"Even though we can calculate how much dark matter there is in the universe, we still know little about what dark matter is. The particles in dark matter must either have a lot of mass, or there must be very many of them. Neutrinos meet all the requirements of dark matter. But there is one big difficulty. They have far too little mass." Raklev is now trying to prove that dark matter consists of gravitinos. This is a particle that has been unfairly treated for years. Gravitinos are the supersymmetric partner of gravitons.

Or, to be even more precise: "The gravitino is the hypothetical, supersymmetric partner of the hypothetical particle graviton, so it is also impossible to predict a more hypothetical particle than this," laughs Raklev (below), who writes on his web pages that he is looking for dark material both under his sofa and other places.

 

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In order to dig deeper into why Raklev believes dark matter consists of gravitinos, and have any chance at all of understanding the theory behind gravitinos, Apollon has to take a couple of steps back: Step 1: Supersymmetry Physicists want to find out whether or not nature is supersymmetric. Supersymmetry means that there is a symmetry between matter and forces. For each type of electron and quark there is a corresponding heavy, supersymmetric partner. The supersymmetric particles were created in the instant after the Big Bang. If some of them have survived to today, they may be what dark matter is made of.

The supersymmetric partner of the gravitino is, as Apollon said, the graviton.  "A graviton is the particle we believe mediates gravitational force, just like a photon, the light particle, mediates electromagnetic force. While gravitons do not weigh anything at all, gravitinos may weigh a great deal. If nature is supersymmetric and gravitons exist, then gravitinos also exist. And vice versa. This is pure mathematics." But there is a small but. Physicists cannot demonstrate the relationship between gravitons and gravitinos before they have managed to unify all the forces of nature.

Step 2: The forces of nature One of the biggest things physicists long to do is to unify all the forces of nature in a single theory. In the middle of the last century physicists discovered that electricity and magnetism were part of the same force of nature. This force has since been called electromagnetism. Two of the other forces of nature are the strong nuclear force and the weak nuclear force. The weak nuclear force can be seen in, among things, radioactivity. The strong nuclear force is ten billion times as strong and binds together neutrons and protons.

In the 1970s, electromagnetism was unified with the strong and weak nuclear forces in what physicists call the standard model. The fourth force of nature is gravity. Even though it is unbelievably painful to fall down stairs, gravity is the weakest of the four forces of nature. The problem is that physicists have not yet been able to unify gravity with the three other forces of nature.

The day physicists gain a unified understanding of all four forces of nature, they will gain a unique understanding of the world. This will make it possible to describe all imaginable interactions between all possible particles in nature. Physicists call this the ToE Theory (Theory of Everything). In order to unify gravitational force with the other three forces of nature we have to understand gravity as quantum theory. This means we need a theory in which the particle graviton is included in the atomic nucleus.

Researchers are now looking for signs of both supersymmetry and the ToE Theory. Discovering the graviton would be an enormous step in this direction. Reveals dark matter As the reader may have understood, it is very difficult to research dark matter. This is because dark matter has no electromagnetic relationships to terrestrial particles at all.

One example of dark matter is the aforementioned neutrino. Unfortunately, neutrinos make up only an imperceptibly tiny part of dark matter. Even though it has not been possible to observe dark matter, several billion neutrinos race through your body every second. However, their speed is somewhat limited. The particles move just as slowly as the speed the solar system moves around the galaxy.

In other words, a mere 400 kilometres a second. "When there are no electromagnetic relationships with visible particles, the particles can pass right through us without any measuring instruments detecting them. This is where supersymmetry comes in. If supersymmetry is right, physicists can explain why there is dark matter in the universe. That is what is fun about my job," laughs Raklev. He is now asserting that dark matter mostly consists of gravitinos.

"Supersymmetry simplifies everything. If the ToE Theory exists, in other words if it is possible to unify the four forces of nature, gravitinos must exist." The gravitinos were formed right after the Big Bang. "A short time after the Big Bang we had a soup of particles that collided. Gluons, which are the force bearing particles in the strong nuclear force, collided with other gluons and emitted gravitinos. Many gravitinos were formed after the Big Bang, while the universe was still plasma. So we have an explanation of why gravitinos exist."

Physicists have up to now viewed gravitinos as a problem. They have believed that the theory of supersymmetry does not work because there are too many gravitinos. "Physicists have therefore strived to eliminate gravitinos from their models. We, on the other hand, have found a new explanation that unifies the supersymmetry model with dark matter that consists of gravitinos. If dark matter is not stable, but just very long lived, it is possible to explain how dark matter consists of gravitinos."

In the old models dark matter was always everlasting. This meant that gravitinos were a bothersome part of the supersymmetry model. In Raklev's new model, their life span is no longer endless. Nonetheless, the average life span of gravitinos is very long and actually longer than the life span of the universe. However, there is a big difference between an unending life span and a life span of more than 15 billion years. With limited a life span, gravitinos must be converted into other particles. It is precisely this conversion effect that can be measured. And the conversion explains the model.

"We believe that almost all dark matter is gravitinos. The explanation lies in very hard mathematics. We are developing special models that calculate the consequences of these theories and we predict how the particles can be observed in experiments." The measurements are underway Researchers are now trying to test this experimentally and explain why these new particles have not yet been seen in the CERN experiments in Geneva in Switzerland.

"On the other hand, it should theoretically possible to observe them from a space probe." The simplest way of observing gravitinos could be studying what happens if two particles collide out in the universe and are converted into other particles such as photons or antimatter. Even though the collisions occur very rarely, there is still so much dark matter in the universe that a significant number of photons should be able to be produced.

The big problem is that gravitinos do not collide. "At least it happens so rarely that we could never hope to observe it." Nonetheless there is hope. "Luckily for us, gravitinos are not one hundred per cent stable. They are converted into something else at some point. We can predict what the signal looks like after gravitinos have been converted. The conversion will send out a small electromagnetic wave. This is also called a gamma ray."

NASA's Fermi-LAT space probe is currently measuring gamma rays. A number of research groups are now analysing the data. "So far we have only seen noise. But one of the research groups claim they have observed a small, suspicious surplus of gamma rays from the centre of our galaxy. Their observations may fit our models," says Raklev.

The Daily Galaxy via University of Oslo

Comments

So now we are making up a new particle, the gravitino, because we need a partner for another particle we have made up, the graviton. And we need these to explain gravity, which was also made up once upon a time. (See "Gravity Doesn't Exist" or "The Situation of Gravity")

"Without this dark matter it is impossible to explain how the visible things in the universe hang together."
Impossible? Stupidity lvl OVER 9000 detected

I don't even want to read the rest of the article, knowing what a piece of crap it is. Junk science is not real science, it is a fairy tale for grownups.

But theories are just educated guesses, fairy tales if that's what you choose to call them. Science moves forward by proving or disproving theories. Today's junk science may be tomorrow's accepted fact...or not.

The only things we can definately not prove or disprove are the thoughts (theories) we haven't had.

You wrote, "In the middle of the last century physicists discovered that electricity and magnetism were part of the same force of nature. This force has since been called electromagnetism."

Surely you meant to write "in the middle of the 19th century..."

I'm curious about something. This very website, among many, has posted about the discovery of dense amounts of material surrounding galaxies, that was undetectable 80 years ago by the technology the time, and one article even stated that this material now visible to modern technology, accounts for the gravitational discrepancies that gave rise to the theory of dark matter.

So - why is dark matter still 'on the table'?

2Hal9000.
Dark matter is unfalsifiable, therefore does not belong to science, it belongs to philosophy. Why "rapid expansions of space" occurs at the scale of clusters and superclusters, where we can never study and test it? Oh, how convenient...

"Gravitinos" --Will They Unlock the Mystery of Dark Matter in the Universe?

Of course not - they don´t exist.

Shouldn't the superpartner of graviton be the graviton again? That is to say, shouldn't the graviton be identical with its superpartner in similar way, like the photon is identical with antiphoton?

This sentence, "Thanks to gravity this dark matter clumps together as ordinary matter." doesn't make sense. Not only is the syntax awkward but, if you mean to say dark matter clumps together, that is untrue. There are no dark matter stars or planets. This is explained by dark matter not interacting with itself electromagnetically. Therefore it does not clump.

The Universe is not driven by the weakest force in Nature known as "gravity" - some ten to the power of 39 times weaker than proton-proton or electron-electron repulsion, or electron-proton attraction - but by electromagnetism and plasma physics. It's an Electric Universe, maybe infinite and eternal. Gravity is probably electrical - you don't think the most massive dinosaurs could have been able to stand up, let alone walk and run or fly, in the Earth's present-day gravity and atmosphere, do you?

If the universe were driven by attraction-only gravity, it would have collapsed long ago. It most surely stands to reason that for the very big jobs, Nature would use the strongest attractive and repulsive forces at its disposal - the electric forces and fields. The Big Bang [Once upon a time that did not yet exist, there was nothing - which exploded], Black Holes, neutron stars, dark matter, dark energy, warped spacetime and other fancy gobbledygook are impossible, laughable absurdities. Without Einstein, but with a Maxwell-Lorentz ether, a gravity-driven universe would never have got off the ground.

“Cloud & rain model,” the model of Universe structure expects:
-Dark matter is particles of compressed atom structure matter. That is when in atoms, electrons and protons/neutrons get compressed together to become extremely small. Dark matter will convert into standard matter, when it get pressure drop, temperature drop and speed drop.
-Dark matters (fleeting at extremely high speed) fill the cosmos as cosmic atmosphere that are responsible to cause low redshift sky objects (z around1.4) sky objects all over the sky, because of belated light effect (source coming earlier than light) of objects travelling faster enough than light. Regardless their directions, objects travelling faster enough than light will never blueshift.
- High redshift sky objects (z>5) have tendency to correlate with the area around Ursa Major & Leo. “Car model” expect this area is the post of Universe nucleus hiding.
-High redshift sky objects (z around>1.4) fleet back toward Universe nucleus due to gravity of dying galaxies becoming stronger than dragging force of dark matter wall (cosmic atmosphere).

“Cloud & rain model,” the model of Universe structure expects:
-Space isn’t expanding. Sky objects really travels in relation with their redshift/blueshift. Universe has nucleus, and galaxies (while persistently leaving Universe nucleus) grow. By ageing, the galaxies will be condensed getting more compact. Then when they get too dense, the dying galaxies will fleet back to Universe nucleus. We watch high redshift (z around>1.4) sky objects all over the sky, because of belated light effect (source coming earlier than light) of objects travelling faster enough than light. Regardless their directions, objects travelling faster enough than light will never blueshift.

Balderdash!

And poorly written balderdash at that!

Sorry but The big Bang is just a fancy name given to something that nobody really knows how everything has come or was originated from !!

Friends do or say whatever u want but just don't believe in an electromagnetically driven, colorful, ever-radiant plasma universe..plasma cosmology is good only for writing sci fi stories.


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