Theoretical Astronomy

Inflation and the Landscape of String Theory ( CANCELLED )

One of major advances of string theory in recent years was an understanding that vacuum solutions with potentially viable four-dimensional cosmology come in a plethora of an incredibly large and rich 'landscape' of string theory vacua. The number of possible vacua and, in turn, types of Universes, may exceed 10 to the power 1000.

Mysteries of the oscillations of gas accreting onto black holes, neutron stars, and white dwarfs

Dr. Wagoner will survey the QPOs (quasi-periodic oscillations) seen in the luminosity fluctuation power spectra of compact objects accreting from a binary companion star. There is little understanding of the different frequency relationships in these systems. Dr. Wagoner will focus on the theory and observations of black holes, and compare the predictions of their spin via diskoseismolgy with those from two other methods.

Are we living in a multiverse? Eternal inflation, bubbles, and cosmic collisions

About a decade ago, we completed an epochal transformation in the understanding of our cosmos, unraveling a broad and deep understanding of how the observable universe has evolved from a hot, dense state 13.7 billion years ago.  Yet a second, even bigger transformation may now be taking place, because this understanding points to a crucial early epoch of "inflationary" cosmic expansion, during which it expanded at a stupendous rate to create the vast amount of space we can observe.  But cosmologists are coming to believe that inflation may do much more: in many versions, inflation goes on f

Do We Need String Theory to Quantize Gravity?

The strong, weak, and electromagnetic interactions all have consistent, relativistic and quantum mechanical descriptions in terms of pointlike particles, but Einstein's theory of gravitation has long resisted a similar treatment, because of severe ultraviolet divergences. String theory solves these problems, but it introduces a new length scale, perhaps 16 orders of magnitude below what can be tested experimentally.

Dark Matter: The Other Universe

A startling discovery in science in the past few decades is most mass in the universe is in "dark matter"- some very clever form of matter capable of speeding up the motion of stars and galaxies while eluding direct detection at the same time. Dr. Ma will summarize the evidence for the existence of dark matter, discuss what it can and cannot be, and describe ongoing research on this mysterious component of the universe.

Understanding the Star Formation Rate

Stars are the engines of the Universe: nuclear reactions within them are the only significant source of non-gravitational power in the cosmos, the source of all heavy elements, and the cradles of life. However, the process by which stars form remains poorly understood, and one mystery in particular stands out: what sets the star formation rate? In this talk Dr. Krumholz will review our understanding of the rate at which stars form, both observationally and theoretically. 

Don't Rain on my Planet: The Importance of Clouds and Hazes for Understanding Exoplanets and Brown Dwarfs

Clouds and hazes shape the observed spectra of exoplanets and brown dwarfs. Yet we know from Earth that clouds and hazes are inherently difficult to model and are the leading source of uncertainty in terrestrial GCM forecasts of globals warming. Dr. Marley will review what we know about the chemistry and physics of clouds in substellar atmospheres and discuss some pathways to haze formation in exoplanet atmospheres.

Building a habitable planet: the physics and chemistry of planet formation

 Habitable planets must not only reside in a narrow range of distances from their stars, but they also must contain water and carbon. This is easier said than done. In this talk, IDr. Kress will discuss the chemistry in protoplanetary disks, and the physical processes by which earth-like planets form. In particular, Dr. Kress will focus on how habitable planets obtain carbon and water, the key ingredients for life. 

Observing String Multiverse with Astrophysical Black Holes

One of the most intriguing and controversial recent ideas in cosmology and string theory is that the Universe is highly inhomogeneous on the length scales much longer than its currently observable part, with many of the fundamental "constants" of Nature varying on the ultra-long length scales. Our location in this cosmic landscape is to a large extent determined by requiring that the local particle physics parameters should allow for life to develop. Dr.

Water, Molecular Oxygen and Ice in Star-Forming Molecular Clouds

The Oxygen is the third most abundant element in the universe and its molecules (oxygen, water, carbon dioxide) a basic ingredient of life on Earth. Oxygen chemistry in the interstellar molecular clouds which form stars and planets has long been a mystery. We discuss that mystery and propose its resolution in this talk. Its resolution also suggests a way to synthesize complex carbon molecules in interstellar clouds and in protoplanetary disks.


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