Tag Archives: Research stars

Dark energy –  UC supernova analysis  reframes debate

The accelerating expansion of the Universe may not be real, but could just be an apparent effect, according to new research published in the journal Monthly Notices of the Royal Astronomical Society.

The new study—by a group at the University of Canterbury in Christchurch, New Zealand—finds the fit of Type Ia supernovae to a model universe with no dark energy to be very slightly better than the fit to the standard dark energy model.

Dark energy is usually assumed to form roughly 70% of the present material content of the Universe. However, this mysterious quantity is essentially a place-holder for unknown physics.

Current models of the Universe require this dark energy term to explain the observed acceleration in the rate at which the Universe is expanding. Scientists base this conclusion on measurements of the distances to supernova explosions in distant galaxies, which appear to be farther away than they should be if the Universe’s expansion were not accelerating.

However, just how statistically significant this signature of cosmic acceleration is has been hotly debated in the past year. The previous debate pitted the standard Lambda Cold Dark Matter (ΛCDM) cosmology against an empty universe whose expansion neither accelerates nor decelerates. Both of these models though assume a simplified 100 year old cosmic expansion law—Friedmann’s equation.

Friedmann’s equation assumes an expansion identical to that of a featureless soup, with no complicating structure. However, the present Universe actually contains a complex cosmic web of galaxy clusters in sheets and filaments that surround and thread vast empty voids.

Professor David Wiltshire, who led the study from the University of Canterbury in Christchurch, said, ”The past debate missed an essential point; if dark energy does not exist then a likely alternative is that the average expansion law does not follow Friedmann’s equation.”

Rather than comparing the standard ΛCDM cosmological model with an empty universe, the new study compares the fit of supernova data in ΛCDM to a different model, called the ’timescape cosmology’. This has no dark energy. Instead, clocks carried by observers in galaxies differ from the clock that best describes average expansion once the lumpiness of structure in the Universe becomes significant. Whether or not one infers accelerating expansion then depends crucially on the clock used.

The timescape cosmology was found to give a slightly better fit to the largest supernova data catalogue than the ΛCDM cosmology. Unfortunately the statistical evidence is not yet strong enough to rule definitively in favour of one model or the other, but future missions such as the European Space Agency’s Euclid satellite will have the power to distinguish between the standard cosmology and other models, and help scientists to decide whether dark energy is real or not.

Deciding that not only requires more data, but also better understanding  properties of supernovae which currently limit the precision with which they can be used to measure distances. On that score, the new study shows significant unexpected effects which are missed if only one expansion law is applied. Consequently, even as a toy model the timescape cosmology provides a powerful tool to test our current understanding, and casts new light on our most profound cosmic questions.

Fighting hospital acquired infections

Check out the role of UC researchers in this video ‘Saving Lives with Active Black’

Nosocomial infections (hospital acquired infections) are one of the leading causes of patient mortality in healthcare environments. Numerous ideas and products are being developed to reduce the transmission of pathogens that are incidentally spread on touch surfaces by hospital staff and visitors between surface cleanings. The research group had an idea to use a hard ceramic coating that is also “self-cleaning”. This very interesting material – Titanium Dioxide is a well-known “self-cleaning” material because it absorbs UV-light, produces oxygen radicals and burns off dirt. Read more and consider voting>

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Call for Research Report stories – UC’s best and brightest

The Research Report is an excellent opportunity to profile some of UC’s best and brightest.

Copies are sent to key contacts in business, industry, education and the political sphere. Around 30 stories are published each year. One of the goals of the report is to demonstrate, through feature articles and across all disciplines, the real world impact of research at UC.

2017 theme: The focus of the 2017 Research Report will be on UC’s doctoral research and will consider the role of the student, the research and the supervisory team.

If you have an idea for a feature that supports the 2017 theme, please take a little time to fill in the following questions and return it marked Subject: Research Report,  to: communications@canterbury.ac.nz  by end of day Friday 22 September.

If you have any queries regarding the Research Report, please contact Grant Barrie in Research and Innovation: ext 95667 or  grant.barrie@canterbury.ac.nz

Read the Research Report 2016 here and find archives of the report here.

  1. Story angle/relevance : Describe your story idea, how it relates to the theme, and why it presents an opportunity for UC.
  1. What is the ‘need to know?’ What, where, who, why, when. Bullet points on this are welcome.
  1. Why would this research matter to someone who is not a staff member or student at UC? What is the real-world impact? How will it improve society?
  1. Timeliness for Research Report 2017 – what dates are driving this research? Acknowledging that postgraduate research takes place over a number of years, why is the research relevant / continue to be relevant in 2017? Is something in particular happening, or anticipated?
  1. Who is involved? Please list the student, research team and supervisory team. Please ensure both the supervisor and student are happy to put the story idea forward.
  1. Photo/video opportunities? Is there something unique? What opportunities are there for a powerful, dramatic photograph that adds value to the story, or even makes the cover? Is there a dynamic highly visual opportunity that would look great on video?

Note: Research Report stories are frequently repurposed across all UC communication channels, e.g. as blogs, media releases or via social media.

We very much look forward to receiving your ideas for features by end of day Friday 22 September to communications@canterbury.ac.nz

Grant Barrie
Research & Innovation