Yashar Akrami

Has DESI detected exponential quintessence? The new Dark Energy Spectroscopic Instrument (DESI) DR2 results have strengthened the possibility that dark energy is dynamical, i.e., it has evolved over the history of the Universe. One simple, but ...

Here is our recent paper, where we have shown that quintessence provides a very good fit to the DESI dark energy data, better than the cosmological constant, and that it prefers a curved universe:
arxiv.org/abs/2504.04226

08.04.2025 18:42 — 👍 2    🔁 1    💬 0    📌 0

To CPL, or not to CPL? What we have not learned about the dark energy equation of state We show that using a Taylor expansion for the dark energy equation-of-state parameter and limiting it to the zeroth and first-order terms, i.e., the so-called Chevallier-Polarski-Linder (CPL) parametr...

To both cosmology and string theory communities: do not use simple phenomenological parametrizations (e.g., truncated Taylor expansions) of dark energy equation of state to conclude whether or not dark energy is dynamical -- see our recent paper:

arxiv.org/abs/2503.22529

02.04.2025 07:40 — 👍 8    🔁 1    💬 0    📌 3

Cosmic topology. Part IIIb. Eigenmodes and correlation matrices of spin-2 perturbations in orientable Euclidean manifolds We study the eigenmodes of the spin-2 Laplacian in orientable Euclidean manifolds and their implications for the tensor-induced part of the cosmic microwave background (CMB) temperature and polarizati...

Here is our new COMPACT collaboration paper, where we demonstrate that cosmic microwave background (CMB) polarization measurements from upcoming experiments can provide new avenues for detecting cosmic topology (i.e., the shape of the Universe):
arxiv.org/abs/2503.08671

16.03.2025 15:03 — 👍 3    🔁 0    💬 0    📌 0

Cosmologists Try a New Way to Measure the Shape of the Universe | Quanta Magazine Is the universe flat and infinite, or something more complex? We can’t say for sure, but a new search strategy is mapping out the subtle signals that would reveal if the universe had a shape.

Acoustic signatures in the cosmic microwave background could help researchers infer the shape of the universe.
www.quantamagazine.org/cosmologists...

27.01.2025 15:51 — 👍 68    🔁 20    💬 2    📌 3

Is the universe a sphere, like the surface of Earth? Or maybe it’s shaped like a doughnut? Cosmologists believe that these possibilities could leave clues in the sky. New methods could help find them. https://buff.ly/3PTCOTo

28.01.2025 21:55 — 👍 44    🔁 13    💬 1    📌 2

Cosmologists Try a New Way to Measure the Shape of the Universe | Quanta Magazine Is the universe flat and infinite, or something more complex? We can’t say for sure, but a new search strategy is mapping out the subtle signals that would reveal if the universe had a shape.

Is the universe infinite, or does it have a hidden shape waiting to be discovered? 🌌

Yashar Akrami (@yasharakrami.bsky.social) from #IFT is leading groundbreaking research on cosmic topology, featured in Quanta Magazine!

Read more:
www.quantamagazine.org/cosmologists...

28.01.2025 13:21 — 👍 5    🔁 1    💬 0    📌 0

Quanta Magazine just published a story about our searches for the topology of the Universe:

27.01.2025 16:38 — 👍 1    🔁 0    💬 0    📌 0

Glad you liked it - thank you for joining!

11.12.2024 15:26 — 👍 0    🔁 0    💬 0    📌 0

Having Persian dinner with IFT's cosmology group. What a wonderful evening it was! @iftuamcsic.bsky.social

11.12.2024 08:00 — 👍 3    🔁 0    💬 0    📌 0

This is great, @mmylova.bsky.social, thanks!

25.11.2024 04:32 — 👍 1    🔁 0    💬 0    📌 0