New research from the Harvard-Smithsonian Center for Astrophysics suggests that oscillating heavy particles generated “clocks” in the primordial universe that could be used to determine what produced the initial conditions that gave rise to the universe.
How did the universe begin? And what came before the Big Bang? Cosmologists have asked these questions ever since discovering that our universe is expanding. The answers aren’t easy to determine. The beginning of the cosmos is cloaked and hidden from the view of our most powerful telescopes. Yet observations we make today can give clues to the universe’s origin. New research suggests a novel way of probing the beginning of space and time to determine which of the competing theories is correct.
The most widely accepted theoretical scenario for the beginning of the universe is inflation, which predicts that the universe expanded at an exponential rate in the first fleeting fraction of a second. However a number of alternative scenarios have been suggested, some predicting a Big Crunch preceding the Big Bang. The trick is to find measurements that can distinguish between these scenarios.
One promising source of information about the universe’s beginning is the cosmic microwave background (CMB) — the remnant glow of the Big Bang that pervades all of space. This glow appears smooth and uniform at first, but upon closer inspection varies by small amounts. Those variations come from quantum fluctuations present at the birth of the universe that have been stretched as the universe expanded.
The conventional approach to distinguish different scenarios searches for possible traces of gravitational waves, generated during the primordial universe, in the CMB. “Here we are proposing a new approach that could allow us to directly reveal the evolutionary history of the primordial universe from astrophysical signals. This history is unique to each scenario,” says coauthor Xingang Chen of the Harvard-Smithsonian Center for Astrophysics (CfA) and the University of Texas at Dallas.
While previous experimental and theoretical studies give clues to spatial variations in the primordial universe, they lack the key element of time. Without a ticking clock to measure the passage of time, the evolutionary history of the primordial universe can’t be determined unambiguously.
“Imagine you took the frames of a movie and stacked them all randomly on top of each other. If those frames aren’t labeled with a time, you can’t put them in order. Did the primordial universe crunch or bang? If you don’t know whether the movie is running forward or in reverse, you can’t tell the difference,” explains Chen.
This new research suggests that such “clocks” exist, and can be used to measure the passage of time at the universe’s birth. These clocks take the form of heavy particles, which are an expected product of the “theory of everything” that will unite quantum mechanics and general relativity. They are named the “primordial standard clocks.”
Subatomic heavy particles will behave like a pendulum, oscillating back and forth in a universal and standard way. They can even do so quantum-mechanically without being pushed initially. Those oscillations or quantum wiggles would act as clock ticks, and add time labels to the stack of movie frames in our analogy.
“Ticks of these primordial standard clocks would create corresponding wiggles in measurements of the cosmic microwave background, whose pattern is unique for each scenario,” says coauthor Yi Wang of The Hong Kong University of Science and Technology. However, current data isn’t accurate enough to spot such small variations.
Ongoing experiments should greatly improve the situation. Projects like CfA’s BICEP3 and Keck Array, and many other related experiments worldwide, will gather exquisitely precise CMB data at the same time as they are searching for gravitational waves. If the wiggles from the primordial standard clocks are strong enough, experiments should find them in the next decade. Supporting evidence could come from other lines of investigation, like maps of the large-scale structure of the universe including galaxies and cosmic hydrogen.
And since the primordial standard clocks would be a component of the “theory of everything,” finding them would also provide evidence for physics beyond the Standard Model at an energy scale inaccessible to colliders on the ground.
This research is detailed in a paper (Quantum Primordial Standard Clocks) by Xingang Chen and Mohammad Hossein Namjoo (CfA/UT Dallas) and Yi Wang (The Hong Kong University of Science and Technology). It has been accepted for publication in the Journal of Cosmology and Astroparticle Physics and is available online.
Reference: “Quantum Primordial Standard Clocks” by Xingang Chen, Mohammad Hossein Namjoo and Yi Wang, 4 February 2016, Journal of Cosmology and Astroparticle Physics.
DOI: 10.1088/1475-7516/2016/02/013
arXiv:1509.03930
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2 Comments
Well! CMB is the primordial standard clock If a used to trace the origin of the Universe. But we want to peep into the period before BIG BANG took place which is out of our scientific range. What is certain is that Big Bang had happened and inflation started with expanding universe and birth of all the fundamental quarks, atoms, Matter, Stars ,Galaxies, Nebulae, anti-matter, fundamental four forces and even Dark Matter. If a crunch and then expansion had happened at the time of birth of the Universe, then what we are foreseeing is an oscillating Universe. If the small variation in the pattern of Cosmic Microwaves can confirm this crunch, then the same argument can be extended to include many many previous oscillating Universe and even Multi Universe model. The fact that light speed and other electromagnetic waves is capped by “c”=3 X 10^10 cms per second makes our observation limited. God has curtailed our range of observation like this and we have to satisfy ourselves only by such hypothesis at the best. Travelling back in time before the origin of the Universe is imaginary only like square root of -1 , which is ‘i’ but the complex number gives many useful results however.Thank You.
“The most widely accepted theoretical scenario for the beginning of the universe is inflation.” I have read that there are several issues to Inflation such as how it stopped everywhere at the same time w/o “quantum fluctuations” and that the initial conditions needed to start Inflation is MUCH less likely than the Universe forming as we see it today w/o Inflation. But I never hear about any of this in articles. Inflation is still always referred to as a given fact. Any comments?