New Theory on Dark Matter, Dark Energy

Grav
Fg indicates the force, a indicates the acceleration

A fascinating new paper released today suggest that both dark matter and dark energy can be explained by a single phenomenon – particles of matter with negative mass. I give a link to the paper below, but I will attempt a quick layman’s explanation.

Fundamentally, orthodox positive-mass attracts other positive-mass, and negative-mass would repel other negative-mass. The interesting part is the interaction between positive-mass and negative-mass particles. The positive-mass particle is repelled, but the negative-mass particle is attracted i.e. the positive-mass ‘runs away’ but the negative-mass ‘follows’.

The scientist behind this new theory, has run computer simulations which show that a galaxy would indeed become surrounded by a halo of negative mass particles, and that this halo would exert a kind of pressure on the orthodox matter galaxy, maintaining, for example, its spiral shape in rotation. This is important because it is understood that without some kind of dark matter influence, the spiral arms of a galaxy would not rotate fast enough to maintain their shape, indeed not fast enough to be consistent with observations. This is one of the reasons dark matter is theorised in the first place.

The other aspect of this theory is that because the negative mass particles, outside of the halos, are repelling each other, they exert an outward pressure, like a gas, which can be interpreted as the cause of the expansion of the universe. However this would require continual creation of such particles to keep up the expansive pressure. My gut feeling is that this is the weakest proposal in the theory, particularly since the author points out the beauty of having negative mass particles to balance the orthodox positive mass particles – everything else of course has balance – positive and negative electrical charges, magnetic poles…

Link to scientific article

 

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Dark matter wind blowing past the Sun

When galaxies collide, and several have merged into our own Milky Way, there are imprints that show as streams of stars, which are all moving in the same direction, but not yet equilibrated into the usual spiral arm rotation.

DMFlow
Artists impression: C. O’Hare; NASA/Jon Lomberg

One such stream, the S1 stream, is of particular interest since it crosses the path of our sun. Thinking about the dark matter from the merged galaxy, this would imply that there is a dark matter “wind” blowing past us at about 500km/s. This could potentially help in our efforts to detect the components of dark matter in earth-bound experiments.

However it is possible that the dark matter from a merger would follow a different trajectory from the stars, since we know that the dark matter in a galaxy does not occupy the same geometric shape as the stars in that galaxy. Indeed dark matter may not have the same equivalence of gravitational and inertial mass.

Phys. Rev. D 98, 103006 (2018)

Our Galaxy is atypically positioned in the cosmos

The overall grand structure of the universe is that galaxies are scattered along filaments surrounding voids as illustrated in the simulation below:

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The large-scale structure of the universe.     Credit: Millennium Simulation Project

Two studies, one from 2013 and one from 2017, now confirm that not only is our own galaxy,  the Milky Way, located atypically in a void rather than a filament, but also that it is located in the largest known void – about 7 times larger than an average void.

The original study came to this conclusion on the basis of galaxy catalogues, whereas the new study measures the motions of galaxies by measuring changes to the energy of Cosmic Background Radiation which has passed through those galaxies. The motions of galaxy clusters indicates those regions of higher gravitational attraction. The two studies, by different means, are consistent.

This, statistically, is a very surprising result. It might suggest that there is something wrong with the underlying theory behind astrophysical measurements, it might be a statistical fluke, or there might be an, as yet, unthought-of explanation.

Live Science article

Nano-dumbbell used to test vacuum friction

Rotor
Credit: Tongcang Li/Purdue University

Researchers at Purdue University fabricated a tiny, nanoscale rotor from silica, and then levitated it in a vacuum, blasting it with circularly polarised light from a laser to set it spinning. The size of the dumbbell is 170 x 320 nanometers (you could lay 200 of these dumbbells end to end across a human hair) and the rate of spin achieved is an incredible 60 billion rotations per minute.

Whilst this is all very impressive, what really caught my eye is that the device is being used to research the nature of friction in a vacuum. Of course there are no actual particles in a vacuum to slow the spinner down – the friction effect which the researchers are measuring is exerted by virtual particles which pop into and out of existence in a vacuum!

Research Paper

Live Science article

ANITA anomoly – Unknown particles challenge the Standard Model

Cosmic rays have been detected coming up from the Antarctic ice. The cosmic ray detection experiment, ANITA, is intended to detect rays coming from space, but has detected high-energy particles coming upwards from the ice. This is bizarre because high-energy particles stand an infinitesimally small chance of penetrating right through the earth without interacting with anything. Furthermore, IceCube, the neutrino detection experiment has now also confirmed detection of upward high-energy particles, and a paper on preprint today calculates that whatever particle is doing this, has much less than a 1-in-3.5 million chance of being part of the Standard Model!

There are murmurs of this being the first evidence of Super symmetry, sterile neutrinos, atypical dark matter, stau sleptons (the super symmetrical version of a tau lepton) – indeed there were theoretical papers written years ago predicting that the stau slepton would be detected in neutrino observatories.

Clearly there will now be considerable effort to attain more detection data.

Link to Live Science article

Link to pre-print paper

Ancient retrovirus causes addictive behaviour

Some evolutionary mutations to human genes have been cause by the ability of ancient retroviruses to insert themselves (randomly) into our genes. One such retrovirus is HK2 – It’s activity was relatively recent (250,000 years) and it is only present in 5 – 10% of humans, inserted into the RASGRF2 gene, which is part of the Dopamine release pathway – the reward feedback circuit.

Two studies communicated today, show that

(a) those who contracted HIV through IV drug use are 2.5 times more likely to have the HK2 mutation than those who contracted HIV through sex.

(b) those who contracted Hepatitis C through IV drug use were 3.6 times more likely to have the HK2 mutation to RASGRF2 than those who contracted Hep C in other ways.

Then, to establish whether the clear implication that addictive behaviour is associated with this HK2 on RASGRF2 mutation, researchers then took normal human brain cells in vitro, and precisely duplicated the mutation. Sure enough the effect was to increase Dopamine expression in the cells, confirming that the reward pathway would be affected by that mutation.

FRBs in the news again

Fast Radio Bursts are one of my favourite astronomical phenomena, because their cause or origin is still completely unknown. They are very short bursts of radio-frequency radiation, lasting just a few milliseconds, but of colossal intensity. There have been only about 37 catalogued to date, all one-offs except FRB 121102.

FRB121102 is a “repeater” – a series of bursts were observed coming from the same source in 2012, then again on several days in 2015, and 15 more bursts during 30 minutes in 2017. The origin appears to be a galaxy about 2 billion light years away.

Although spinning black holes and neutron stars are possible candidate for generating the FRBs, there is no regularity of pulse in the transmissions as there is with spinning pulsars. One outside, but not discounted, possibility is that the source of the FRBs is some sort of extraterrestrial intelligent action – an attempt at communication or the utilisation of power for some purpose.

The new news is that researchers have re-analysed the data from August 26, 2017, when 21 bursts were detected, and they have found another 72 pulses by using AI – a convolutional neural network.

Link to Research paper

Link to Space.com article

Update 8th Jan 2019: A new Canadian Observatory called CHIME has reported finding another 13 FRBs including another repeater.

Update 14th February 2019: Observations reported today suggest that Superluminous Supernovae give rise to magnetars that then emit FRBs. More observations to follow.

Scientific American article