The Great Cold Spot in the cosmic microwave background

The Great Cold Spot in the cosmic microwave background: The CMB cold spot is not particularly colder than other cold regions of the CMB, but it is unusual because it is a particularly cold region surrounded by a rather warm region. Simulations of random fluctuations in a CMB estimate that the odds of such a cold spot happening in the universe is about 1 in 100. So it's possible that it is just a random fluctuation. But the 1% odds is small enough that some astronomers have looked for a possible cause, and these ideas have ranged from the mundane to the wild.

Ask Ethan #49: Do the cosmic unknowns cast doubt on the Big Bang? — Starts With A Bang! — Medium

Ask Ethan #49: Do the cosmic unknowns cast doubt on the Big Bang? — Starts With A Bang! — Medium:  ...all isotropic, homogeneous spacetimes (that is, solutions to GR that are roughly the same at all locations in space and in all directions) must either have expanding or contracting space...

All of this — the whole story I outlined above — would be true regardless of what else is actually in your Universe. The only things that change due to dark matter and dark energy are the following...

Embrace the lumpiverse: How mess kills dark energy - physics-math - 25 June 2014 - New Scientist

Embrace the lumpiverse: How mess kills dark energy - physics-math - 25 June 2014 - New Scientist: Wiltshire takes issue with the last of the motions used to make the dipole anisotropy disappear: a movement at a speed of 635 kilometres per second of the entire Local Group towards a "great attractor" somewhere in the distant Hydra-Centaurus supercluster of galaxies...

They claim the galaxies' movements make most sense if the Local Group isn't moving at all. Instead, the greater density of matter towards Hydra-Centaurus is slowing the universe's expansion along our line of sight, giving us the impression of such a movement. A comparative void in the other direction, meanwhile, is producing the opposite effect, causing an area of faster expansion behind us. The effects of the inhomogeneities along this axis are comparatively local, occurring on scales up to about 300 million light years, and only alter the universe's expansion rate by some 0.5 per cent. But they are sufficient to account for nearly all of the dipole anisotropy – and so colour our view of the entire universe...

This suggests that the age of the universe could be as much as 18.6 billion years in places where a low density of matter means the clock has ticked particularly fast. Our own smaller estimate of the universe's age is a natural consequence of sitting in an area of unusually high density: a galaxy.

Big Bang breakthrough team back-pedals on major result - physics-math - 19 June 2014 - New Scientist

Big Bang breakthrough team back-pedals on major result - physics-math - 19 June 2014 - New Scientist: The paper published today is significant because it is the first time the researchers themselves have dialled back on their original claims...

"It seems that real data from Planck is indicating that these dust models are under-estimates," says Pryke. "The prior knowledge of dust at these latitudes in our field of view has gone up and so the confidence in the gravitational wave component has gone down."

Backlash to Big Bang Discovery Gathers Steam - Scientific American

Backlash to Big Bang Discovery Gathers Steam - Scientific American: Spergel also says the BICEP2 team evidently failed to factor in contamination from the cosmic infrared background radiation that comes from distant, dusty galaxies. “When you do that,” Spergel says, “it’s probably enough to account for the entire signal they’re seeing.

Blockbuster Big Bang Result May Fizzle, Rumor Suggests | Science/AAAS | News

Blockbuster Big Bang Result May Fizzle, Rumor Suggests | Science/AAAS | News: To subtract the galactic foreground, BICEP researchers relied on a particular map of it generated by the European Space Agency's spacecraft Planck, which mapped the CMB across the entire sky from 2009 until last year. However, the BICEP team apparently interpreted the map as showing only the galactic emissions. In reality, it may also contain the largely unpolarized hazy glow from other galaxies, which has the effect of making the galactic microwaves coming from any particular point of the sky look less thoroughly polarized than they actually are. So using the map to strip out the galactic foreground may actually leave some of that foreground in the data where it could produce a spurious signal, Falkowski explains.

A Mathematical Proof That The Universe Could Have Formed Spontaneously From Nothing — The Physics arXiv Blog — Medium

A Mathematical Proof That The Universe Could Have Formed Spontaneously From Nothing — The Physics arXiv Blog — Medium: The new proof is based on a special set of solutions to a mathematical entity known as the Wheeler-DeWitt equation...

In each of these cases, they find a solution in which the bubble can expand exponentially and thereby reach a size in which a universe can form—a Big Bang...

Cosmologists cast doubt on inflation evidence

Cosmologists cast doubt on inflation evidence: Inflation may very well be the cause—and Dent and company state right off the bat that "there is little doubt that inflation at the Grand Unified Scale is the best motivated source of such primordial waves" –  but there's also a possibility, however remote, that some other, later cosmic event is responsible for at least some if not all of the BICEP2 measurements.

Cosmologists Say Last Week’s Announcement About Gravitational Waves and Inflation May Be Wrong — The Physics arXiv Blog — Medium

Cosmologists Say Last Week’s Announcement About Gravitational Waves and Inflation May Be Wrong — The Physics arXiv Blog — Medium: Many cosmologists think that the same kind of phases changes occurred in the universe after inflation. Each phase change began in different regions at slightly different times...

This self-ordering process would have been hugely violent, generating its own gravitational waves that rippled through spacetime, albeit after inflation. Could this process be responsible for the polarisation that the BICEP2 team has measured?...

...a small improvement in the data could firmly rule out self-ordering as the origin of the signal.

First glimpse of big bang ripples from universe's birth - physics-math - 17 March 2014 - New Scientist

First glimpse of big bang ripples from universe's birth - physics-math - 17 March 2014 - New Scientist: Inflation should have stretched the very first gravitational waves created during the big bang, taking them from imperceptible wavelengths to a size we can detect in the CMB... Rippling gravitational waves would subtly change the polarisation pattern, twisting the CMB into distinctive swirls called B-modes...

"We see a big excess of power, and it looks exactly like the gravitational wave signal that we had been seeking," says Pryke. "There's a huge zoo of inflationary models, but if we look at the simplest ones, they would predict values in the ballpark that we're seeing..."

"If gravity were not quantised, inflation would not produce gravitational waves," says Guth.

Did a hyper-black hole spawn the Universe? : Nature News & Comment

Did a hyper-black hole spawn the Universe? : Nature News : ...in the bulk universe the event horizon of a 4D black hole would be a 3D object — a shape called a hypersphere. When Afshordi’s team modeled the death of a 4D star, they found that the ejected material would form a 3D brane surrounding that 3D event horizon, and slowly expand.


The authors postulate that the 3D Universe we live in might be just such a brane — and that we detect the brane’s growth as cosmic expansion. “Astronomers measured that expansion and extrapolated back that the Universe must have begun with a Big Bang — but that is just a mirage,” says Afshordi.

The model also naturally explains our Universe’s uniformity...

Hubble bubble may explain different measurements of expansion rate of the universe

Hubble bubble may explain different measurements of expansion rate of the universe:  One way to determine the Hubble constant... is based on measuring the cosmic microwave background radiation... can also be derived from the movement of galaxies near the Milky Way, movement largely due to the expansion of the universe. "When you compare the results from the two methods, there is a deviation of about 9 percent..."

...The bubble describes regions of the universe where the density of matter falls below the cosmic average. "Until now knowledge of our cosmic neighbourhood has been too imprecise to determine whether or not we are in such a bubble", continues Dr. Marra. "But let's just assume for a moment that our Milky Way is located in a Hubble Bubble. Matter outside the bubble would then attract nearby galaxies so strongly that they would move more quickly than average. In this case we would measure a higher Hubble constant that would apply to our cosmic neighbourhood, but not to the universe as a whole."

Ultracold Big Bang experiment successfully simulates evolution of early universe

Ultracold Big Bang experiment successfully simulates evolution of early universe: Physicists have reproduced a pattern resembling the cosmic microwave background radiation in a laboratory simulation of the Big Bang, using ultracold cesium atoms in a vacuum chamber at the University of Chicago...


It turns out that under certain conditions, a cloud of atoms chilled to a billionth of a degree above absolute zero (-459.67 degrees Fahrenheit) in a vacuum chamber displays phenomena similar to those that unfolded following the Big Bang, Hung said.

"At this ultracold temperature, atoms get excited collectively. They act as if they are sound waves in air," he said. The dense package of matter and radiation that existed in the very early universe generated similar sound-wave excitations, as revealed by COBE, WMAP and the other experiments.

The synchronized generation of sound waves correlates with cosmologists' speculations about inflation in the early universe. "Inflation set out the initial conditions for the early universe to create similar sound waves in the cosmic fluid formed by matter and radiation," Hung said.

Ultracold Big Bang experiment successfully simulates evolution of early universe | UChicago News

Ultracold Big Bang experiment successfully simulates evolution of early universe | UChicago News: These excitations are called Sakharov acoustic oscillations, named for Russian physicist Andrei Sakharov, who described the phenomenon in the 1960s. To produce Sakharov oscillations, Chin’s team chilled a flat, smooth cloud of 10,000 or so cesium atoms to a billionth of a degree above absolute zero, creating an exotic state of matter known as a two-dimensional atomic superfluid.

Then they initiated a quenching process that controlled the strength of the interaction between the atoms of the cloud. They found that by suddenly making the interactions weaker or stronger, they could generate Sakharov oscillations.

The universe simulated in Chin’s laboratory measured no more than 70 microns in diameter, approximately the diameter as a human hair.

Swirls in the Afterglow of the Big Bang Could Set Stage for Major Discovery | Science/AAAS | News

Swirls in the Afterglow of the Big Bang Could Set Stage for Major Discovery | Science/AAAS | News . In a patch of sky, the random polarization pattern can be separated into two superimposed components: B-modes, in which the polarization forms right- or left-handed swirls, and E-modes, in which it does not. Whereas the coalescing of matter in the early universe can produce only E-modes, gravity waves rippling along during inflation should produce B-modes. The intensity of those "primordial" B-modes should reveal the energy density of the universe during inflation and help explain how it happened.

Blow for 'dark flow' in Planck's new view of the cosmos

Blow for 'dark flow' in Planck's new view of the cosmos: This flow suggested that the universe had somehow become lopsided, as if space-time itself was behaving like a tilted table and matter was sliding off...
The latest search is based on a new, higher-resolution map of the cosmic microwave background from Planck. The Planck team says their multi-pronged analysis also found no evidence of galaxy clusters gushing along in a coherent stream.

Planck shows almost perfect cosmos – plus axis of evil

Planck shows almost perfect cosmos – plus axis of evil: "The overall conclusion is that standard cosmology is an extremely good match to Planck data," said Efstathiou. "If I were an inflationary theorist I would be extremely happy."

...Planck reveals that one half of the universe has bigger variations than the other. Planck's detectors are over 10 times more sensitive and have about 2.5 times the angular resolution of WMAP's, giving cosmologists a much better look at this alignment. "We can be extremely confident that these anomalies are not caused by galactic emissions and not caused by instrumental effects..."

The Measurement That Would Reveal The Universe As A Computer Simulation - Technology Review

The Measurement That Would Reveal The Universe As A Computer Simulation - Technology Review: The question that Beane and co ask is whether the lattice spacing imposes any kind of limitation on the physical processes we see in the universe...

They say that the lattice spacing imposes a fundamental limit on the energy that particles can have. That's because nothing can exist that is smaller than the lattice itself.

So if our cosmos is merely a simulation, there ought to be a cut off in the spectrum of high energy particles...


"The most striking feature...is that the angular distribution of the highest energy components would exhibit cubic symmetry in the rest frame of the lattice, deviating significantly from isotropy," they say.

Giant fractals are out – the universe is a big smoothie - New Scientist - New Scientist

Giant fractals are out - the universe is a big smoothie: They tested for clusters by placing any given galaxy in the centre of an imaginary sphere and counted the number of galaxies within it. If clustering exists, there should be more galaxies within a sphere than if the 220,000 galaxies were distributed randomly throughout the huge cube.

With relatively small spheres – up to about 330 million light years wide – they did find galactic clusters. But in larger spheres the number of galaxies met expectations for randomness.

Galactic 'axis of asymmetry' threatens cosmic order - New Scientist - New Scientist

Galactic 'axis of asymmetry' threatens cosmic order: In most directions, Longo found an even spread of right and left-handed galaxies. But when he looked along a line about 25 degrees off from the direction of the Milky Way's north pole - a cosmic reference point that sits directly above the centre of our galaxy - he found more left-handed spirals than right-handed ones...
Now, Lior Shamir of the Lawrence Technological University at Southfield, Michigan, has automated the process and looked deeper into space. His software classified the handedness of almost 250,000 spiral galaxies up to 3.4 billion light years away, which were surveyed by SDSS and another project called the Galaxy Zoo...

This time, though, the axis of asymmetry pointed about 60 degrees to the other side of the Milky Way's north pole (see diagram). Despite being separated by 85 degrees, both axes have such large uncertainties that they could be aspects of the same axis.
"The observation is so strange that it's difficult to interpret its meaning," says Shamir. "A pattern in the structure of the universe at such a large scale is not something that we expect to see."