Early Universe and BBN ASTR/PHYS 4080: Intro to Cosmology Week 9 - - PowerPoint PPT Presentation

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early universe and bbn

Early Universe and BBN ASTR/PHYS 4080: Intro to Cosmology Week 9 - - PowerPoint PPT Presentation

Nov 12, 2022 337 likes •553 views

Early Universe and BBN ASTR/PHYS 4080: Intro to Cosmology Week 9 ASTR/PHYS 4080: Introduction to Cosmology Spring 2018: Week 09 1 Early Universe Timescales ASTR/PHYS 4080: Introduction to Cosmology Spring 2018: Week 09 2 Early Universe

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Early Universe and BBN

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ASTR/PHYS 4080: Intro to Cosmology Week 9

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Early Universe Timescales

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Early Universe Timescales

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Early Universe Timescales

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Nuclear Binding Energy

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release energy expect nucleosynthesis to result in all atoms becoming iron does not happen - why not?

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

neutron-proton ratio

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

ASIDE: Reionization Signature

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hydrogen hyperfine transition (electron spin flips) emits photon at 21cm (1.4 GHz) can observe at high (z~10) redshifts and see the first stars ionizing the neutral gas formed at recombination https://youtu.be/kifF3RYcfn0

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

ASIDE: Reionization Signature

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

ASIDE: Reionization Signature

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Deuterium Synthesis

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Making He

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release energy after 200s, all non-decayed neutrons could end up in a D nucleus, BUT D reactions can also occur: more likely

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Making He

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release energy Tritium and He-3 quickly interact with

ther particles to form He-4:

Strong force reactions: large cross- sections and fast rates End up with mostly He-4, since it’s so tightly bound

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Making He

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release energy Can’t add p or n to He-4 to make a new atom, so have to use later products to form Li/Be nuclei Stable He-4 is made quickly, but harder to form higher A elements so their creation is slower no stable nuclei

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

BBN

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BBN

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Abundances from Nucleosynthesis

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Creation process depends on relative abundances at any given time, so have to calculate computationally Nucleosynthesis doesn’t run to completion like in stars — rapidly dropping temperature cuts it off and “freezes” abundance pattern Exact yields depend most on baryon- to-photon ratio: (determines temperature of nucleosynthesis)

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Measuring BBN

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quasar absorption lines CMB

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Lithium Problem

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Solution?

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Spring 2018: Week 09 ASTR/PHYS 4080: Introduction to Cosmology

Baryon-Antibaryon Asymmetry

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no leftover antimatter from the early universe: Standard Model predicts existence of antimatter equally likely should be 1 quark-antiquark pair for every 2 photons in the early universe when temperature drops, quarks annihilate but are no longer produced —> universe should be entirely photons! must be a small asymmetry!