I How Can Gravitational Lensing Help Detect Dark Energy?

[Chronos]

This paper; https://arxiv.org/abs/1701.03418, Direct Probe of Dark Energy through Gravitational Lensing Effect, addresses a potential means to measure dark energy over cosmological distances. Perhaps I am a bit slow, but, I found the basic idea sufficiently simple and obvious that I am surprised it hasn't been suggested before. Perhaps it was, and it merely eluded my attention. I feel flooded with questions I cannot yet even fully articulate. A couple which have surfaced include - 1] How might reverse lensing due to DE impact the apparent angular size of remote structures in the universe? 2] How might this affect the Friedmann equations?

 

[Chalnoth]

This paper; https://arxiv.org/abs/1701.03418, Direct Probe of Dark Energy through Gravitational Lensing Effect, addresses a potential means to measure dark energy over cosmological distances. Perhaps I am a bit slow, but, I found the basic idea sufficiently simple and obvious that I am surprised it hasn't been suggested before. Perhaps it was, and it merely eluded my attention. I feel flooded with questions I cannot yet even fully articulate. A couple which have surfaced include - 1] How might reverse lensing due to DE impact the apparent angular size of remote structures in the universe? 2] How might this affect the Friedmann equations?

I could be wrong, but at first blush it sounds to me like they're making a very basic error. The thing that ultimately curves light paths in the universe is the geometry of space-time. Since Dark Energy doesn't cluster (it can't to have the properties it has), its impact is going to be just the impact of curvature that appears in the Friedmann equations, where the only effect that looks like lensing stems from the spatial curvature parameter.

Maybe I'm wrong. I'm sure other cosmologists will weigh in on the paper within the next few weeks. But it really does not seem right to me.

 

[Mordred]

I agree they are not factoring out other contributors to the curvature. This paper is under the assumption of removal of matter/radiation fields.

I don't see any thing new here Everything on the would be true in a Lamba only toy universe. Unless I too am mistaken. So thanks for sharing Chronos

Though for scalar field modelling its got a good collection of relevant formulas P.

edit I have to double check but quintessence seems off as well. I need to dig out the correct textbooks I have on it. Yeah there is something off with what they have for quintessence. The tracker field w_q is time varying according to both wiki and Matt Roose. However to be completely honest I'm not really sure. So I dug up a review on it just in case anyone is interested.

https://arxiv.org/abs/1304.1961

Probably not important enough to go through a lot of effort lol

 

[Chronos]

That dark energy is evenly distributed across the cosmos appears to explain why the lensing effect is only detectable across cosmological distances.