David Weir [he/him/his] - davidjamesweir

HIP and University of Helsinki

Helsinki LISA day, 27.2.2020

Credit: Stephan Paul, arXiv:1205.2451

Credit: Stephan Paul, arXiv:1205.2451

Credit: Stephan Paul, arXiv:1205.2451

- Process by which the Higgs 'switched on'
- In the Standard Model it is a crossover
- Possible in extensions that it would be
*first order*

➥ colliding bubbles then make gravitational waves

Credit:
[FDL] GRAN
via Wikimedia Commons; Morrissey and
Ramsey-Musolf, arXiv:1206.2942

- Study (often on lattice) theories of physics beyond
the Standard Model with nonperturbative methods:
- Do they have first-order phase transitions?
- What regions of parameter space are viable?

- Study (often with simulations) real-time
production of gravitational waves from phase
transitions:
- Can we create ansätze for the power spectrum?
- If we see something at LISA, what can we say about the underlying phyics?

- $T_*$, temperature
- $T_* \sim 100 \, \mathrm{GeV} \longrightarrow \mathrm{mHz}$ today

- $\alpha_{T_*}$, vacuum energy fraction
- $v_\mathrm{w}$, bubble wall speed
- $H_*/\beta$, 'duration'

These link our two areas of interest:

BSM models and GW
production.

- Given $\{T_*, \alpha_{T_*}, v_\mathrm{w}, \beta/H_*\}$, what GW signal do we get?
- Simulate the transition with an effective model, with:
- Scalar field $\phi$ (the Higgs 'turning on')
- Relativistic fluid (everything else - a hot plasma)

⬇︎ ?

[Here: $Z_2$-symmetric xSM points from arXiv:1910.13125]

Source: arXiv:1903.11604

strong transitions

is released as latent heat)

Credit: Daniel Cutting

- Mark Hindmarsh, Kari Rummukainen
**Oli Gould**, Asier Lopez-Eiguren,*Tuomas Tenkanen**Daniel Cutting*, Jani Dahl, Lauri Niemi**Anna Kormu****Satumaaria Sukuvaara**,**Essi Vilhonen**

- Next few years:
**GW Cosmology for LISA**- Cutting-edge simulations of the early universe
- Microscale (Monte Carlo) to macroscale (hydro)
- Dark and visible sectors

- After that:
**The Energy and Gravity Frontiers**- Electroweak phase transition and
beyond:

CEPC (2030-), ILC (2035-) - Finnish role in European GW missions:

Einstein Telescope (2030-), LISA (2034-) - Complementarity between GW and colliders

- Electroweak phase transition and
beyond: