How Does Christine Dantas Explore Quantum Gravity Through Astrophysics?

[marcus]

Christine is interested in astrophysical tests of Quantum Gravity
(like AUGER and GLAST, the first of which has already started)

she is an astrophysicist at the brazil National Institute of Space Research (if I get it right). I think she is a postdoc or beginning faculty

I really like her interests which combine observational astrophysics, with QG and cosmology. this is to be on the ball!

anyway she has just started a QG blog, which is also a good idea I think. It is about time to do it.

http://christinedantas.blogspot.com/2005/11/astrophysical-probes-of-quantum.html

http://christinedantas.blogspot.com

 

[marcus]

some of us were introduced to Christine Dantas last year in John Baez TWF #206 where she has a comment near the end about a Bekenstein paper
http://math.ucr.edu/home/baez/week206.html

it says her institute is INPE
http://www.inpe.br/english/

Institute National of Space Research, I guess.
Instituto Nacional de Pesquisas Espaciais

it is in the city of São José dos Campos, in the state of São Paulo

here are some Dantas papers going back to 1997
http://arxiv.org/find/grp_physics/1/au:+Dantas_C/0/1/0/all/0/1

some of these papers are co-authored with someone whose name rings a bell for some reason, the name is de Carvalho. Here are his papers:
http://arxiv.org/find/astro-ph/1/au:+Carvalho_R/0/1/0/all/0/1
maybe his name rings a bell because he has published a lot in peer-review astrophysics journals. Anyway Reinaldo de Carvalho is ALSO at this institute INPE

so this is a rough idea of coordinates of this blog.

I think it is a really good idea to have blog that has, in its field of vision, the gradually arriving stage of observational QG------and incidentally QC, quantum cosmology!

Bojowald just posted a paper about LQC that discusses some observational possibilities. Roy Maartens at Portsmouth gave the main LQC phenomenology talk at Loops '05.

Both Bojowald and Roy Maartens should be told about Dantas blog. Also Parampreet Singh at Penn State should know about it. He is very much into LQG phenomenology---that means the prospects for TESTING.

GOOD LUCK ON THE BLOG CHRISTINE!

 

[marcus]

Requardt---The Continuum Limit of Discrete Geometries

Christine Dantas has flagged an interesting paper in her blog, one that I didn't know about.

Here is her entry
http://christinedantas.blogspot.com/2005/11/continuum-limit-of-discrete-geometries.html

Here is the paper. It's by someone at Göttingen

http://arxiv.org/abs/math-ph/0507017
The Continuum Limit of Discrete Geometries
Manfred Requardt
29 pages

"In various areas of modern physics and in particular in quantum gravity or foundational space-time physics it is of great importance to be in the possession of a systematic procedure by which a macroscopic or continuum limit can be constructed from a more primordial and basically discrete underlying substratum, which may behave in a quite erratic and irregular way. We develop such a framework within the category of general metric spaces by combining recent work of our own and ingeneous ideas of Gromov et al, developed in pure mathematics. A central role is played by two core concepts. For one, the notion of intrinsic scaling dimension of a (discrete) space or, in mathematical terms, the growth degree of a metric space at infinity, on the other hand, the concept of a metrical distance between general metric spaces and an appropriate scaling limit (called by us a geometric renormalisation group) performed in this metric space of spaces. In doing this we prove a variety of physically interesting results about the nature of this limit process, properties of the limit space as e.g. what preconditions qualify it as a smooth classical space-time and, in particular, its dimension."

Requardt's work connects to Loll CDT because he is studying metric (non-manifold) structures which are rough enough to have no fixed dimensionality------they can have, say, microscopic 2D but higher at larger scale increasing to, say, macroscopic 4D.

Manfred Requardt has a scary haircut.
But however he writes well----he is a physicist but he can also organize his thoughts into theorems with efficient proofs, like a mathematician---which can be a good way to communicate clearly. At least this is my first impression.

I don't know if I think he is on a good track, it is too early for me to have any guesses, but I see that what he is doing could shed some light on the picture of spacetime growing up from work of both Loll and Reuter

I think Christine is neat because she is an ASTROPHYSICIST who knows about observational tests of QUANTUM GRAVITY (she even lists ten or so papers about this) which is a upcoming field that many people do not even know is starting! But she ALSO knows about something entirely different from the QG phenomenology and testing, namely the still-very-tentative new model of spacetime at a fundamental level, that is shaping up

these are two very different research developments and she is perceptive about both