8,146 research outputs found
Cosmology Solved? Quite Possibly!
The discovery of the cosmic microwave background (CMB) in 1964 by Penzias and
Wilson led to the establishment of the hot big-bang cosmological model some ten
years later. Discoveries made in 1998 may ultimately have as profound an effect
on our understanding of the origin and evolution of the Universe. Taken at face
value, they confirm the basic tenets of Inflation + Cold Dark Matter, a bold
and expansive theory that addresses all the fundamental questions left
unanswered by the hot big-bang model and holds that the Universe is flat,
slowly moving elementary particles provide the cosmic infrastructure, and
quantum fluctuations seeded all the structure seen in the Universe today. Just
as it took a decade to establish the hot big-bang model after the discovery of
the CMB, it will likely take another ten years to establish the latest addition
to the standard cosmology and make the answer to ``Cosmology Solved?'',
``YES!'' Whether or not 1998 proves to be a cosmic milestone, the coming
avalanche of high-quality cosmological data promises to make the next twenty
years an extremely exciting period for cosmology.Comment: 19 pages LaTeX including 5 eps figures. Presented at Great Debate:
Cosmology Solved?, October 4, 1998, Baird Auditorium, Smithsonian Natural
History Museum, Washington, DC. To be published in Proc. Astron. Soc.
Pacific, February 199
In the Beginning: American Physics, the Kansas Science Education Standards, and the Attack on Scientific Cosmology
While the battle over teaching evolution in American public schools significantly predates
the infamous 1925 Scopes, or \"Monkey,\" Trial, the battle over teaching physics has
just begun. In August, 1999, the Kansas Board of Education voted to drop not only the theory
of evolution from state science standards, but to remove the Big Bang theory of cosmic
origins as well. It is important to view the Board\'s actions in the context of contemporary
American culture, and its changing attitude toward physics. For much of the twentieth century, theoretical and experimental physics was viewed as good for American progress and
essential to American defense. Now, however, the field is seen by an increasing number of
Americans to be both irrelevant and a drain on the country\'s financial resources. Recognizing
this shift is essential to understanding the new vulnerability of physics to proponents of
creationism. Understanding why the shift is occurring is essential to any defense
Report from the Tri-Agency Cosmological Simulation Task Force
The Tri-Agency Cosmological Simulations (TACS) Task Force was formed when
Program Managers from the Department of Energy (DOE), the National Aeronautics
and Space Administration (NASA), and the National Science Foundation (NSF)
expressed an interest in receiving input into the cosmological simulations
landscape related to the upcoming DOE/NSF Vera Rubin Observatory (Rubin),
NASA/ESA's Euclid, and NASA's Wide Field Infrared Survey Telescope (WFIRST).
The Co-Chairs of TACS, Katrin Heitmann and Alina Kiessling, invited community
scientists from the USA and Europe who are each subject matter experts and are
also members of one or more of the surveys to contribute. The following report
represents the input from TACS that was delivered to the Agencies in December
2018.Comment: 36 pages, 3 figures. Delivered to NASA, NSF, and DOE in Dec 201
ASCR/HEP Exascale Requirements Review Report
This draft report summarizes and details the findings, results, and
recommendations derived from the ASCR/HEP Exascale Requirements Review meeting
held in June, 2015. The main conclusions are as follows. 1) Larger, more
capable computing and data facilities are needed to support HEP science goals
in all three frontiers: Energy, Intensity, and Cosmic. The expected scale of
the demand at the 2025 timescale is at least two orders of magnitude -- and in
some cases greater -- than that available currently. 2) The growth rate of data
produced by simulations is overwhelming the current ability, of both facilities
and researchers, to store and analyze it. Additional resources and new
techniques for data analysis are urgently needed. 3) Data rates and volumes
from HEP experimental facilities are also straining the ability to store and
analyze large and complex data volumes. Appropriately configured
leadership-class facilities can play a transformational role in enabling
scientific discovery from these datasets. 4) A close integration of HPC
simulation and data analysis will aid greatly in interpreting results from HEP
experiments. Such an integration will minimize data movement and facilitate
interdependent workflows. 5) Long-range planning between HEP and ASCR will be
required to meet HEP's research needs. To best use ASCR HPC resources the
experimental HEP program needs a) an established long-term plan for access to
ASCR computational and data resources, b) an ability to map workflows onto HPC
resources, c) the ability for ASCR facilities to accommodate workflows run by
collaborations that can have thousands of individual members, d) to transition
codes to the next-generation HPC platforms that will be available at ASCR
facilities, e) to build up and train a workforce capable of developing and
using simulations and analysis to support HEP scientific research on
next-generation systems.Comment: 77 pages, 13 Figures; draft report, subject to further revisio
Primordial Density Perturbation in Effective Loop Quantum Cosmology
It is widely believed that quantum field fluctuation in an inflating
background creates the primeval seed perturbation which through subsequent
evolution leads to the observed large scale structure of the universe. The
standard inflationary scenario produces scale invariant power spectrum quite
generically but it produces, unless fine tuned, too large amplitude for the
primordial density perturbation than observed. Using similar techniques it is
shown that loop quantum cosmology induced inflationary scenario can produce
scale invariant power spectrum as well as small amplitude for the primordial
density perturbation without fine tuning. Further its power spectrum has a
qualitatively distinct feature which is in principle falsifiable by observation
and can distinguish it from the standard inflationary scenario.Comment: 33 pages, revtex4, few typos and a confusing notation changed;
several clarifications, references added, to appear in CQ
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