....Alternatives to Inflation in Primordial Power Spectrum

In summary, the study discusses the use of massive fields in the primordial universe as standard clocks to identify different scenarios of the primordial universe. This new mechanism shows that these fields can leave scale-dependent oscillatory signals in the power spectrum, providing a model-independent way to understand the early universe. However, current observations and data analysis methods have not been able to detect these signals, leading to the possibility of alternative theories of cosmogenesis. Further studies and analysis are needed to determine the detectability of these signals and their implications for the leading theory of cosmic inflation.
  • #1
Spinnor
Gold Member
2,216
430
Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum

"Massive fields in the primordial universe function as standard clocks and imprint clock signals in the density perturbations that directly records the scale factor of the primordial universe as a function of time, a(t). A measurement of such signals would identify the specific scenario of the primordial universe in a model-independent fashion. In this Letter, we introduce a new mechanism through which quantum fluctuations of massive fields function as standard clocks. The clock signals appear as scale-dependent oscillatory signals in the power spectrum of alternative scenarios to inflation."

From, https://arxiv.org/abs/1809.02603

From, https://www.quantamagazine.org/a-new-test-for-the-leading-big-bang-theory-20180911/

"The leading hypothesis about the universe’s birth — that a quantum speck of space became energized and inflated in a split second, creating a baby cosmos — solves many puzzles and fits all observations to date. Yet this “cosmic inflation” hypothesis lacks definitive proof. Telltale ripples that should have formed in the inflating spatial fabric, known as primordial gravitational waves, haven’t been detected in the geometry of the universe by the world’s most sensitive telescopes. Their absence has fueled underdog theories of cosmogenesis in recent years. And yet cosmic inflation is wriggly. In many variants of the idea, the sought-after ripples would simply be too weak to observe."
Universe_lede1300.jpg


An all-sky map of the local universe derived from the 2MASS Extended Source Catalog of more than 1.5 million galaxies. The Milky Way is shown at the center, and other galaxies are color-coded by their distances, obtained from several different galaxy surveys.

See also, https://dailygalaxy.com/2018/09/the...xes-the-big-bang-todays-top-science-headline/
 

Attachments

  • Universe_lede1300.jpg
    Universe_lede1300.jpg
    95 KB · Views: 712
Space news on Phys.org
  • #2
Potentially interesting, but for now it's just a data analysis methods paper. I'll be curious to see it applies to actual data, to see if the signal is actually detectable given reasonable models.
 

1. What is inflation in the context of the primordial power spectrum?

Inflation refers to a period of extremely rapid expansion in the early universe, which is thought to have occurred within the first fractions of a second after the Big Bang. During this period, the universe underwent exponential growth and stretched out any tiny quantum fluctuations into large-scale structures that we see today, including the primordial power spectrum.

2. What are the main alternatives to inflation in explaining the primordial power spectrum?

The main alternatives to inflation include the cyclic model, the ekpyrotic/cosmic bounce scenario, and the pre-Big Bang models. These theories propose alternative mechanisms for the origin of the primordial power spectrum, such as a series of cycles of expansion and contraction, a collision between our universe and another, or a phase of contraction before the Big Bang.

3. How do these alternatives differ from inflation in terms of predictions for the primordial power spectrum?

While inflation predicts a nearly scale-invariant and Gaussian primordial power spectrum, the alternatives have different predictions. For example, the cyclic model predicts an oscillating spectrum, the ekpyrotic scenario predicts a blue spectrum, and the pre-Big Bang models predict a red spectrum. These differences can be tested through observations of the cosmic microwave background radiation.

4. What evidence supports or challenges the inflationary model of the primordial power spectrum?

The main evidence supporting inflation comes from the observation of the cosmic microwave background radiation, which shows a nearly scale-invariant and Gaussian primordial power spectrum. This is consistent with the predictions of inflation. However, there are also some challenges to the inflationary model, such as the horizon problem and the graceful exit problem. These have led to the development of alternative theories.

5. How do these alternatives impact our understanding of the early universe and the formation of structures?

The different alternatives to inflation have different implications for our understanding of the early universe and the formation of structures. For example, the cyclic model suggests that the universe could have existed infinitely in the past, while the ekpyrotic scenario proposes a different mechanism for the creation of structures. Further research and observations are needed to better understand the implications of these alternatives and their impact on our understanding of the early universe.

Similar threads

Replies
1
Views
914
Replies
13
Views
2K
Replies
7
Views
2K
  • Beyond the Standard Models
Replies
8
Views
3K
Replies
1
Views
1K
Replies
5
Views
3K
  • Beyond the Standard Models
Replies
28
Views
4K
  • Beyond the Standard Models
Replies
9
Views
4K
Replies
2
Views
3K
Replies
17
Views
6K
Back
Top