TASI Lectures on the Cosmological Constant

Abstract

The energy density of the vacuum, Lambda, is at least 60 orders of magnitude smaller than several known contributions to it. Approaches to this problem are tightly constrained by data ranging from elementary observations to precision experiments. Absent overwhelming evidence to the contrary, dark energy can only be interpreted as vacuum energy, so the venerable assumption that Lambda=0 conflicts with observation. The possibility remains that Lambda is fundamentally variable, though constant over large spacetime regions. This can explain the observed value, but only in a theory satisfying a number of restrictive kinematic and dynamical conditions. String theory offers a concrete realization through its landscape of metastable vacua.

39 pages, 3 figures

References in corpus (37)

• Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
• Measurements of Omega and Lambda from 42 High-Redshift Supernovae
• de Sitter Vacua in String Theory
• Hierarchies from Fluxes in String Compactifications
• The holographic principle
• Cosmological Constraints from the SDSS Luminous Red Galaxies
• The String Landscape, Black Holes and Gravity as the Weakest Force
• Quantization of Four-form Fluxes and Dynamical Neutralization of the Cosmological Constant
• On the Geometry of the String Landscape and the Swampland
• M Theory, Orientifolds and G-Flux
• Flux compactifications in string theory: a comprehensive review
• The statistics of string/M theory vacua
• Distributions of flux vacua
• From the Big Bang Theory to the Theory of a Stationary Universe
• Disturbing Implications of a Cosmological Constant
• Probabilities in the inflationary multiverse
• Sinks in the Landscape, Boltzmann Brains, and the Cosmological Constant Problem
• Holographic probabilities in eternal inflation
• Fluctuations of the Gravitational Constant in the Inflationary Brans-Dicke Cosmology
• Why is the CMB fluctuation level 10^{-5}?
• Why the cosmological constant is small and positive
• One in a Billion: MSSM-like D-Brane Statistics
• Is There A String Theory Landscape
• Predicting the Cosmological Constant from the Causal Entropic Principle
• Eternal Inflation: The Inside Story
• The landscape of intersecting brane models
• A paradox in the global description of the multiverse
• Towards a gauge invariant volume-weighted probability measure for eternal inflation
• Anthropic prediction for Lambda and the Q catastrophe
• Probabilities in the Bousso-Polchinski multiverse
• A prescription for probabilities in eternal inflation
• Density Perturbations and the Cosmological Constant from Inflationary Landscapes
• A Review of Distributions on the String Landscape
• Landscape Predictions from Cosmological Vacuum Selection
• Geodesic measures of the landscape
• Volume Weighted Measures of Eternal Inflation in the Bousso-Polchinski Landscape
• Anthropic prediction in a large toy landscape

Cited by in corpus (109)

• New Horizons for Fundamental Physics with LISA
• The dark matter crisis: falsification of the current standard model of cosmology
• Echo of interactions in the dark sector
• De Sitter Musings
• The Fine-Tuning of the Universe for Intelligent Life
• Mapping the Cosmological Expansion
• Micromanaging de Sitter holography
• Properties of the scale factor measure
• Life at the Interface of Particle Physics and String Theory
• Where in the String Landscape is Quintessence
• How unimodular gravity theories differ from general relativity at quantum level
• Boltzmann babies in the proper time measure
• Heal the world: Avoiding the cosmic doomsday in the holographic dark energy model
• A small weak scale from a small cosmological constant
• Dynamical compactification from de Sitter space
• Constraining $f(R)$ gravity models with disappearing cosmological constant
• Self-Organised Localisation
• Observational constraints on dark matter-dark energy scattering cross section
• The Degree of Fine-Tuning in our Universe -- and Others
• Cosmological evolution and statefinder diagnostic for new holographic dark energy model in non flat universe
• Quantified naturalness from Bayesian statistics
• The Value of the Cosmological Constant
• The Cosmic Microwave Background: The history of its experimental investigation and its significance for cosmology
• Dark energy: investigation and modeling
• New Interaction between Dark Energy and Dark Matter Changes Sign during Cosmological Evolution
• The Born Rule Dies
• Exacerbating the cosmological constant problem with interacting dark energy
• Exploring Parameter Constraints on Quintessential Dark Energy: the Pseudo-Nambu Goldstone Boson Model
• A geometric solution to the coincidence problem, and the size of the landscape as the origin of hierarchy
• On the implementation of the spherical collapse model for dark energy models
• Cosmological Measures without Volume Weighting
• Predictions from Star Formation in the Multiverse
• TASI lectures on complex structures
• New tracker models of dark energy
• Exploring Parameter Constraints on Quintessential Dark Energy: the Inverse Power Law Model
• Evolution of density perturbations in decaying vacuum cosmology: The case of non-zero perturbations in the cosmological term
• Thermodynamic aspects of dark energy fluids
• Geometric origin of coincidences and hierarchies in the landscape
• Holographic Cosmological Constant and Dark Energy
• Phase Transitions in 4D Gauss-Bonnet-de Sitter Black Holes
• Vacuum Structure and the Arrow of Time
• Sourcing Dark Matter and Dark Energy from $\alpha$-attractors
• Fast optimization algorithms and the cosmological constant
• Naturalness of the relaxion mechanism
• Testing f(R) gravity models with quasar X-ray and UV fluxes
• Cosmological dark energy effects from entanglement
• A Nonlocal Approach to the Cosmological Constant Problem
• Gravitational Mechanisms to Self-Tune the Cosmological Constant: Obstructions and Ways Forward
• Self-interacting holographic dark energy
• Cosmological acceleration
• Crunching Away the Cosmological Constant Problem: Dynamical Selection of a Small $\Lambda$
• $\Lambda (t)$CDM Model as a Unified Origin of Holographic and Agegraphic Dark Energy Models
• Effect of the Trace Anomaly on the Cosmological Constant
• The Cosmological Constant Problem and Re-interpretation of Time
• Constraints on $\Lambda (t)$CDM models as holographic and agegraphic dark energy with the observational Hubble parameter data
• Symmetric-Bounce Quantum State of the Universe
• Stable Large-Scale Perturbations in Interacting Dark-Energy Model
• BRST Quantization of Unimodular Gravity
• Axionic Band Structure of the Cosmological Constant
• Higher Forms and Membranes in 4D Supergravities
• Vacuum energy and the cosmological constant problem in $\kappa$-Poincaré invariant field theories
• Searches for other vacua I: bubbles in our universe
• Emulating $\Lambda$CDM-like expansion on the Phantom brane
• de Sitter Harmonies: Cosmological Spacetimes as Resonances
• Gravitational Waves and Degrees of Freedom in Higher Derivative Gravity
• Energy stored on a cosmological horizon and its thermodynamic fluctuations in holographic equipartition law
• Charged scalar bosons in a Bonnor-Melvin-$\Lambda$ universe at conical approximation
• Perturbed dark energy: classical scalar field versus tachyon
• The Cosmological Constant Problem and Quantum Spacetime Reference Frame
• Agnesi Weighting for the Measure Problem of Cosmology
• Inflation and New Agegraphic Dark Energy
• Non-stationary de Sitter cosmological models
• Bayesian naturalness, simplicity, and testability applied to the $B-L$ MSSM GUT
• Chiral Symmetry and the Cosmological Constant
• Ricci Flow Approach to The Cosmological Constant Problem
• Non-vacum conformally flat space-times: dark energy
• Applications of an exact counting formula in the Bousso-Polchinski Landscape
• The Grand Canonical Multiverse and the Small Cosmological Constant
• The unphysical character of dark energy fluids
• A Local Wheeler-DeWitt Measure for the String Landscape
• Prospects of probing dark energy with eLISA: Standard versus null diagnostics
• Exploring a simple sector of the Einstein-Maxwell landscape
• Radiative stability of tiny cosmological constant from the Swampland and quantized compactification
• Dark Energy and Extending the Geodesic Equations of Motion: Its Construction and Experimental Constraints
• Dark Energy from Quantum Uncertainty of Distant Clock
• Black hole and cosmological analysis of BF sequestered gravity
• Trace Anomaly, Perelman's Functionals and the Cosmological Constant
• A geometric-probabilistic method for counting low-lying states in the Bousso-Polchinski Landscape
• Wormholes supported by a combination of normal and quintessential matter in Einstein and Einstein-Maxwell gravity
• Stability of curvature perturbation with new covariant form for energy-momentum transfer in dark sector
• A technical analog of the cosmological constant problem and a solution thereof
• The Ambiguity in the Definition and Behavior of the Gravitational and Cosmological `Coupling Constants' in the Theory of Induced Gravity
• Phantom scalar emission in the Kerr black hole spacetime
• Schwarzschild black hole in dark energy background
• Late-time Cosmology without Dark Sector but with Closed String Massless Sector
• Inconsistences in Interacting Agegraphic Dark Energy Models
• Weak Gravity Conjecture and Holographic Dark Energy Model with Interaction and Spatial Curvature
• Zero Cosmological Constant and Nonzero Dark Energy from Holographic Principle
• Supersymmetric Inflation from the Fifth Dimension
• Cosmological Equation of State and Interacting Energies
• Anthropic Origin of the Neutrino Mass from Cooling Failure
• Tuning the Cosmological Constant, Broken Scale Invariance, Unitarity
• Linking the Baum-Hawking-Coleman Mechanism with Unimodular Gravity and Vilenkin's Probability Flux
• Uniformly expanding vacuum: a possible interpretation of the dark energy
• Cosmological scenario based on the first and second laws of thermodynamics: Thermodynamic constraints on a generalized cosmological model
• Another Two Dark Energy Models Motivated from Karolyhazy Uncertainty Relation
• Some physical consequences of an exact vacua distribution in the Bousso-Polchinski Landscape
• Bound-state solutions for the charged Dirac oscillator in a rotating frame in the Bonnor-Melvin-Lambda spacetime
• Predicting today's cosmological constant via the Zel'dovich-Holographic connection