Archive for Holographic Principle

Fake News of the Holographic Universe

Posted in Astrohype, The Universe and Stuff with tags , , , , , , on February 1, 2017 by telescoper

It has been a very busy day today but I thought I’d grab a few minutes to rant about something inspired by a cosmological topic but that I’m afraid is symptomatic of malaise that extends far wider than fundamental science.

The other day I found a news item with the title Study reveals substantial evidence of holographic universe. You can find a fairly detailed discussion of the holographic principle here, but the name is fairly self-explanatory: the familiar hologram is a two-dimensional object that contains enough information to reconstruct a three-dimensional object. The holographic principle extends this to the idea that information pertaining to a higher-dimensional space may reside on a lower-dimensional boundary of that space. It’s an idea which has gained some traction in the context of the black hole information paradox, for example.

There are people far more knowledgeable about the holographic principle than me, but naturally what grabbed my attention was the title of the news item: Study reveals substantial evidence of holographic universe. That got me really excited, as I wasn’t previously aware that there was any observed property of the Universe that showed any unambiguous evidence for the holographic interpretation or indeed that models based on this model could describe the available data better than the standard ΛCDM cosmological model. Naturally I went to the original paper on the arXiv by Niayesh Ashfordi et al. to which the news item relates. Here is the abstract:

We test a class of holographic models for the very early universe against cosmological observations and find that they are competitive to the standard ΛCDM model of cosmology. These models are based on three dimensional perturbative super-renormalizable Quantum Field Theory (QFT), and while they predict a different power spectrum from the standard power-law used in ΛCDM, they still provide an excellent fit to data (within their regime of validity). By comparing the Bayesian evidence for the models, we find that ΛCDM does a better job globally, while the holographic models provide a (marginally) better fit to data without very low multipoles (i.e. l≲30), where the dual QFT becomes non-perturbative. Observations can be used to exclude some QFT models, while we also find models satisfying all phenomenological constraints: the data rules out the dual theory being Yang-Mills theory coupled to fermions only, but allows for Yang-Mills theory coupled to non-minimal scalars with quartic interactions. Lattice simulations of 3d QFT’s can provide non-perturbative predictions for large-angle statistics of the cosmic microwave background, and potentially explain its apparent anomalies.

The third sentence (highlighted) states explicitly that according to the Bayesian evidence (see here for a review of this) the holographic models do not fit the data even as well as the standard model (unless some of the CMB measurements are excluded, and then they’re only slightly better)

I think the holographic principle is a very interesting idea and it may indeed at some point prove to provide a deeper understanding of our universe than our current models. Nevertheless it seems clear to me that the title of this news article is extremely misleading. Current observations do not really provide any evidence in favour of the holographic models, and certainly not “substantial evidence”.

The wider point should be obvious. We scientists rightly bemoan the era of “fake news”. We like to think that we occupy the high ground, by rigorously weighing up the evidence, drawing conclusions as objectively as possible, and reporting our findings with a balanced view of the uncertainties and caveats. That’s what we should be doing. Unless we do that we’re not communicating science but engaged in propaganda, and that’s a very dangerous game to play as it endangers the already fragile trust the public place in science.

The authors of the paper are not entirely to blame as they did not write the piece that kicked off this rant, which seems to have been produced by the press office at the University of Southampton, but they should not have consented to it being released with such a misleading title.

Crater 308

Posted in Art, The Universe and Stuff with tags , , , , , on August 1, 2010 by telescoper

I haven’t got time to post much today – WordPress was down earlier when I had a bit of time and now I’m going to watch the highlights of England’s Test victory against Pakistan in the cricket today, which they achieved by bowling out their opponents for only 80 runs in the second innings.

Nevertheless, as a quick filler, I thought it would be nice to show this wonderful image of the crater Daedalus, formerly known as Crater 308, which is located on the far side of the Moon. Not the dark side, by the way, the far side of the Moon gets just as much sunlight as the near side!
This is one of the images I’ve been working on as part of the project Beyond Entropy for a forthcoming exhibit at the Venice Biennale of Architecture which opens at the end of this month. I won’t say too much about the exhibit I’m involved with, except that it explores the way higher-dimensional information can be recorded in surfaces of lower dimension, like a kind of architectural holographic principle. I was particularly struck by the way the pattern of cratering on the Moon yields information about its formation history, which is why I went looking for dramatic examples. This – taken during the Apollo 11 mission- is my favourite image of all those I’ve looked at. I love the complexy topography, its textural contrasts and the way the shadows play across it.

Daedalus is an impact crater that formed about 3.75 to 3.2 bn years ago. It’s about 93km across. The crater looks relatively fresh; showing sharp-ish-looking rims all around with sequences of wonderfully-preserved terraces down onto a pock-marked, flat floor consisting of numerous craterlets and a central peak divided up into two to three well-defined hills. You can also see the effect of more recent impacts in and around it.

Talking of impact, I wonder if I can get this project into our REF submission?