172 research outputs found
TASI Lectures on Remnants from the String Landscape
Superstring theories are very promising theoretically, but the enormous
landscape of string vacua and the (likely) very large underlying string scale
imply that they may never be tested directly. Nevertheless, concrete
constructions consistent with the observed world frequently lead to observable
remnants, i.e., new particles or features that are apparently accidental
consequences of the ultraviolet theory and that are typically not motivated by
specific shortcomings of the standard models of particle physics or cosmology.
For example, moduli, axions, large extended gauge sectors, additional
gauge bosons, extended Higgs/Higgsino sectors, and quasi-chiral exotics are
extremely common. They motivate alternative cosmological paradigms and could
lead to observable signatures at the LHC. Similar features can emerge in other
standard model extensions, but in the stringy case they are more likely to
occur in isolation and not as part of a more complete TeV-scale structure.
Conversely, some common aspects of the infinite "landscape" of field theories,
such as large representations, are expected to be very rare in the string
landscape, and observation of features definitively in the swampland could lead
to falsification. In this article, common stringy remnants and their
phenomenology are surveyed, and implications for indirectly supporting or
casting doubt on string theory are discussed.Comment: v2: 57 pages and references. Citations and comments added, and title
modified. Based in part on lectures by J.H. at TASI 201
An Implication of "Gravity as the Weakest Force"
The negative specific heat of a radiating black hole is indicative of a
cataclysmic endpoint to the evaporation process. In this letter, we suggest a
simple mechanism for circumventing such a dramatic outcome. The basis for our
argument is a conjecture that was recently proposed by Arkani-Hamed and
collaborators. To put it another way, we use their notion of ``Gravity as the
Weakest Force'' as a means of inhibiting the process of black hole evaporation.Comment: 7 pages; v2 some discussion clarifie
Snowmass White Paper: String Theory and Particle Physics
We review recent developments and outstanding questions regarding connecting
the top-down UV complete physical framework of string theory with the observed
physics of the Standard Model and beyond the Standard Model physics,
emphasizing the global nonperturbative framework of F-theory and general
lessons from UV physics. This paper, prepared for the TF01 conveners of the
Snowmass 2022 process, provides a brief synopsis of this important area,
focusing on ongoing developments and opportunities.Comment: 34 pages (17 pages text +17 pages references
Introduction to QCD
These lectures were originally given at TASI and are directed at a level
suitable for graduate students in High Energy Physics. They are intended to
give an introduction to the theory and phenomenology of quantum chromodynamics
(QCD), focusing on collider physics applications. The aim is to bring the
reader to a level where informed decisions can be made concerning different
approaches and their uncertainties. The material is divided into five main
areas: 1) fundamentals, 2) fixed-order perturbative QCD, 3) Monte Carlo event
generators and parton showers, 4) Matching at Leading and Next-to-Leading
Order, and 5) Soft QCD physics.Comment: Lecture notes from a course given at TASI 2012. Last update: July
2017. 85 pages, including index at the back. arXiv admin note: text overlap
with arXiv:1104.286
Non-supersymmetric AdS and the Swampland
We propose to sharpen the weak gravity conjecture by the statement that, except for BPS states in a supersymmetric theory, the gravitational force is strictly weaker than any electric force and provide a number of evidences for this statement. Our conjecture implies that any non-supersymmetric anti-de Sitter vacuum supported by fluxes must be unstable, as is the case for all known attempts at such holographic constructions
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