Dan Hooper Profile picture
May 6, 2019 5 tweets 2 min read Read on X
(1/5) I'm excited about a new paper that I've written with @GordanKrnjaic and Sam McDermott. It combines some of my favorite things: black holes, dark matter, and the Hubble tension.
arxiv.org/abs/1905.01301
#blackholes #cosmology #darkmatter #Hubble
(2/5) If even a small number of black holes were created around the time of inflation, their relative abundance would grow as the universe expands, making it quite plausible that the energy density of the early universe was once dominated by black holes.
(3/5) If these black holes were small, they would quickly Hawking evaporate. Unlike most other particle production mechanisms, this generates all kinds of particles, no matter how feebly interacting -- a promising way to generate dark matter and dark radiation.
(4/5) If the early universe included a black hole dominated era, we find that Hawking radiation will produce dark radiation at a level ΔN_eff∼0.03−0.2 for each light and decoupled species. This range coulld relax the tension between late and early-time Hubble determinations.
(5/5) The dark matter could also originate as Hawking radiation in a black hole dominated early universe, although such dark matter candidates must be very heavy (>10^11 GeV).

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Dan Hooper

Dan Hooper Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @DanHooperAstro

Oct 2, 2020
(1/4) As requested, here is the (provisional) reading list for my class on "Philosophical Problems in Cosmology".

1) Steven Weinberg, To Explain the World
2) Karl Popper, “Science: Conjectures and Refutations”
3)Thomas Kuhn, “The Logic of Discovery of Psychology of Research?”
(2/4)
4) A.J. Ayer, Language, Truth and Logic
5) Dan Hooper, At the Edge of Time
6) Sean Carroll, Something Deeply Hidden
7) Sean Carroll, “Why is there something rather than nothing?”
8) Sean Carroll, “Beyond Falsifiability: Normal Science in a Multiverse”
(3/4)
9) John Ellis and Joseph Silk, “Defend the integrity of physics”
10) Bas Van Fraassen, “Arguments Concerning Scientific Realism”
11) James Robert Brown, “Explaining the Success of Science”
12) David Albert, “NYT Review of ‘A Universe From Nothing’”
Read 4 tweets
Mar 7, 2019
(1/5) Two papers came out this week arguing that there is a robust excess of ~10-20 antiprotons in the cosmic-ray spectrum. Among other reasons, this is exciting because it could be explained by annihilating dark matter.
(2/5) Furthermore, the dark matter mass and annihilation cross section that are required to produce this antiproton excess are the same as those that are required to produce the long-standing Galactic Center gamma-ray excess.
(3/5) The two papers are:
1) A Robust Excess in the Cosmic-Ray Antiproton Spectrum: Implications for Annihilating Dark Matter, by Ilias Cholis, Tim Linden (@trlinden) and myself.
arxiv.org/abs/1903.02549
Read 5 tweets
Jan 9, 2019
(1/6) My Collaborators (Miguel Escudero, @GordanKrnjaic and Mathias Pierre) and I just posted a new paper that I am excited about, "Cosmology With a Very Light L_mu - L_tau Gauge Boson", arxiv.org/pdf/1901.02010…

Let me take a minute to walk you through the main points.
#cosmology
(2/6) We considered a new light particle, a Z' associated with a broken U(1)_mu-tau symmetry, and solved the full set of Boltmann equations to determine how such a particle would impact the energy density in neutrinos and other radiation in the early universe.
#cosmology
(3/6) We found two regions of parameter space that change the expansion history in a way that would help to reconcile the discrepancy between local and cosmological measurements of the Hubble constant. The first of these is the well known region with m_Z' ~ 10-30 MeV.
Read 6 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us!

:(