Archivi tag: early universe

A new approach to exploring quantum gravity

I fisici Lawrence Krauss e Frank Wilczek, rispettivamente dell’Arizona State University e dell’Australian National University, hanno pubblicato un lavoro in cui essi propongono una nuovo approccio sulla possibilità di quantizzare la forza di gravità misurando la polarizzazione della radiazione cosmica di fondo. Secondo gli scienziati, questo metodo potrebbe portare ad una connessione tra la radiazione cosmica di fondo e le onde gravitazionali causate dall’inflazione cosmica durante le epoche primordiali della storia cosmica.

Physicists, as most are aware, have been stymied in their efforts to discover a way to unify quantum mechanics and gravity, most scientists in the field believe there is likely a gravity particle they call it a graviton, that carries the force known as gravity. No one of course has ever seen one, or been able to prove it exists. This is because, they say, of how weak it is compared to the other forces, such as electromagnetism, to be able to see it, some have suggested, would require a device so massive that it would collapse in on itself into a black hole. For this reason, some researchers have suggested that we will never be able to see it.

In their paper, Krauss and Wilczek suggest that it might not be necessary to see it, because there might be a way to infer its existence by measuring the CMB.

Their idea is that in the early Universe, just after the Big Bang, as inflation was occurring, gravitational waves should have been created which in turn would have caused photons present in the CMB to scatter in a certain pattern. Finding that pattern would mean finding evidence of a particle that was carrying the gravitational force, the graviton. And if evidence for the existence of a graviton could be found, then physicists would finally have their “universal theory”. They add that they believe that dimensional analysis could provide a link between those early gravitational waves and Planck’s constant, which is of course used in quantum mechanics. There are a couple of issues with the new theory, the first is that technology does not yet exist to measure the CMB in a way that would allow scientists to detect those early gravitational waves and another is proving that any polarization found in the CMB can indeed be attributable to gravitational waves and not some other mechanism, force or process.

arXiv: Using Cosmology to Establish the Quantization of Gravity
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Galaxy Evolution Over Five Decades

The last few years have seen a transformation in our understanding of the formation and evolution of galaxies. These advances have been driven by observations that cover a broad range in wavelength. In the years ahead, new facilities like the JWST, CCAT, the LMT, ALMA, the JVLA, LOFAR and the SKA will shed further light on how galaxies form by providing huge increases in sensitivity over five decades in wavelength: from the near-infrared to long radio-wavelengths. This conference will bring together researchers from around the world to discuss the current state of the field and future directions that should be taken as these new telescopes come into operation. The meeting is in honour of Professor Malcolm Longair, who has made invaluable contributions to our knowledge of galaxy evolution and to the Astrophysics Group at the Cavendish Laboratory.

Scientific areas to be covered:

  • AGN and Galaxy Evolution
  • Gas in Galaxies
  • The High-redshift Universe and the First Galaxies
  • Galaxy Assembly and Cosmic Star-formation History
  • Galaxy Clusters and the Role of Environment

Understanding complexity in the early Universe with simpler models

Il comportamento statistico di alcuni sistemi complessi, come ad esempio l’Universo primordiale, può essere analizzato se viene ridotto ad un insieme di sistemi più semplici. Oggi due fisici, Petr Jizba della Czech Technical University a Praga e Fabio Scardigli ora alla Kyoto University in Giappone, hanno pubblicato i risultati di un lavoro di ricerca che riguarda le previsioni teoriche del comportamento dinamico di tali sistemi cosmologici.

Their work focuses on complex dynamical systems whose statistical behaviour can be explained in terms of a superposition of simpler underlying dynamics.

They found that the combination of two cornerstones of contemporary physics, namely Einstein’s special relativity and quantum-mechanical dynamics, is mathematically identical to a complex dynamical system described by two interlocked processes operating at different energy scales.

The combined dynamic obeys Einstein’s special relativity even though neither of the two underlying dynamics does. This implies that Einstein’s special relativity might well be an emergent concept and suggests that it would be worthwhile to further develop Einstein’s insights to take into account the quantum structure of space and time (post). To model the double process in question, the authors consider quantum mechanical dynamics in a background space consisting of a number of small crystal-like domains varying in size and composition, known as polycrystalline space. There, particles exhibit an analogous motion to pollen grains in water, referred to as Brownian motion. The observed relativistic dynamics then comes solely from a particular grain distribution in the polycrystalline space. In the cosmological context such distribution might form during the early Universe’s formation. Finally, the authors’ new interpretation focuses on the interaction of a quantum particle with gravity, that, according to Einstein’s general relativity, can be understood as propagation in curved space-time. The non-existence of the relativistic dynamics on the basic level of the description leads to a natural mechanism for the formation of asymmetry between particles and anti-particles. When coupled with an inflationary cosmology, the authors’ approach predicts that a charge asymmetry should have been produced at ultra-minute fractions of seconds after the Big Bang. This prediction is in agreement with constraints born out of recent cosmological observations.

EPJ: Removing complexity layers from the universe’s creation
EPJ C: Special relativity induced by granular space

New hints on primordial galaxies

Le galassie primordiali avevano un aspetto alquanto differente rispetto a quelle che popolano l’Universo oggi. Grazie ad una serie di osservazioni condotte con il Very Large Telescope (VLT) e il telescopio spaziale Hubble (HST), alcuni ricercatori hanno studiato una galassia molto antica, con una accuratezza senza precedenti, e da cui è stato possibile determinare alcuni parametri astrofisici che la caratterizzano, come la massa, la dimensione, il contenuto chimico e il tasso di formazione stellare.

Galaxies are deeply fascinating objects. The seeds of galaxies are quantum fluctuations in the very early Universe and thus, understanding of galaxies links the largest scales in the Universe with the smallest. It is only within galaxies that gas can become cold and dense enough to form stars and galaxies are therefore the cradles of starsbirths”, explains Johan Fynbo, professor at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen. Early in the Universe, galaxies were formed from large clouds of gas and dark matter. Gas is the Universe’s raw material for the formation of stars. Inside galaxies the gas can cool down from the many thousands of degrees it has outside galaxies. When gas is cooled it becomes very dense. Finally, the gas is so compact that it collapses into a ball of gas where the gravitational compresion heats up the matter, creating a glowing ball of gas, a star is born. In the red-hot interior of massive stars, hydrogen and helium melt together and form the first heavier elements like carbon, nitrogen, oxygen, which go on to form magnesium, silicon and iron. When the entire core has been converted into iron, no more energy can be extracted and the star dies as a supernova explosion. Every time a massive star burns out and dies, it hence flings clouds of gas and newly formed elements out into space, where they form gas clouds that get denser and denser and eventually collapse to form new stars. The early stars contained only a thousandth of the elements found in the Sun today. In this way, each generation of stars becomes richer and richer in heavy elements. In today’s galaxies, we have a lot of stars and less gas. In the early galaxies, there was a lot of gas and fewer stars. “We want to understand this cosmic evolutionary history better by studying very early galaxies. We want to measure how large they are, what they weigh and how quickly stars and heavy elements are formed”, explains Johan Fynbo.

The research team has studied a galaxy located approximately 11 billion years back in time in great detail.

Behind the galaxy is a quasar, which is an active black hole that is brighter than a galaxy. Using the light from the quasar, they found the galaxy using the giant telescopes, VLT in Chile. The large amount of gas in the young galaxy simply absorbed a massive amount of the light from the quasar lying behind it. Here they could ‘see’, via absorption, the outer parts of the galaxy. Furthermore, active star formation causes some of the gas to light up, so it could be observed directly. With the Hubble Space Telescope they could also see the recently formed stars in the galaxy and they could calculate how many stars there were in relation to the total mass, which is comprised of both stars and gas. They could now see that the relative proportion of heavier elements is the same in the centre of the galaxy as in the outer parts and it shows that the stars that are formed earlier in the centre of the galaxy enrich the stars in the outer parts with heavier elements. “By combining the observations from both methods – absorption and emission – we have discovered that the stars have an oxygen content equivalent to approx. 1/3 of the Sun’s oxygen content. This means that earlier generations of stars in the galaxy had already built up elements that made it possible to form planets like Earth 11 billion years ago”, conclude Johan Fynbo.

University of Copenaghen: New knowledge about early galaxies
arXiv: Comprehensive Study of a z = 2:35 DLA Galaxy: Mass, Metallicity, Age, Morphology and SFR from HST and VLT

Cosmic Dawn

The aim of the workshop is to have focused discussions on the latest developments regarding our understanding of the formation and evolution of the first galaxies and structures in the Universe. We intend to centre our discussions on:

  •  Formation, growth and properties of the first galaxies
  •  The formation and growth of seed black holes and the impact of the associated feedback onto proto-galaxies
  •  Feedback from stars: chemical, mechanical and radiative; and how these regulate the growth of the first galaxies
  • The role of reionization during the first billion years of galaxy evolution

The aim is to have broad reviews with topics ranging from observations to theoretical modelling, giving emphasis to the key questions observers and theorists are trying to answer, followed by talks focusing on specific topics in detail. We plan on having ample time for discussions in between the sessions.

222° Meeting of the American Astronomical Society

One of the largest astronomy meetings of the year will open to the public for the first time in its history. More than 500 astronomers, journalists and guests will bring their cosmic know-how to Indianapolis next week for the 222nd meeting of the American Astronomical Society (AAS). The conference begins on Sunday (June 2) and runs through June 6 at the Indiana Convention Center; it is the second of two meetings held annually by the AAS. New findings about alien worlds, mysterious dark matter and the Milky Way will be discussed, and this year anyone can take part in the cosmic action. Several presentations on Monday and Tuesday will be geared toward amateurs that decide to pay the fee and attend. The presentations include information about the Hubble Space Telescope, nearby exoplanets, Pluto, and the formation of galaxies in the early universe. In addition to those talks, the society will also hold two free public events during the convention. Throughout the course of the conference, scientists will take part in town hall-style meetings about NASA, the National Science Foundation and other agencies. The latest findings from the badly damaged planet hunting Kepler Space Telescope will be presented as well. Twitter users can follow the conference using the hashtag #AAS222.