scholarly journals EMERGENT SPACETIME AND THE COSMOLOGICAL CONSTANT

2008 ◽  
Vol 23 (14n15) ◽  
pp. 2181-2183 ◽  
Author(s):  
HYUN SEOK YANG
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Einstein Gravity ◽  
Cosmological Constant Problem ◽  
Emergent Gravity ◽  
Flat Spacetime ◽  
Emergent Spacetime ◽  
Dynamical Origin

We address issues on the origin of gravity and the dark energy (or the cosmological constant) from the perspectives of emergent gravity. We discuss how the emergent gravity reveals a noble, radically different picture about the origin of spacetime, which is crucial for a tenable solution of the cosmological constant problem. In particular, the emergent gravity naturally explains the dynamical origin of flat spacetime, which is absent in Einstein gravity.

scholarly journals DARK ENERGY AND EMERGENT SPACETIME

2011 ◽  
Vol 01 ◽  
pp. 266-271
Author(s):  
HYUN SEOK YANG
Keyword(s):  
Dark Energy ◽  
Symplectic Geometry ◽  
Cosmological Constant Problem ◽  
Geometric Framework ◽  
Emergent Gravity ◽  
Flat Spacetime ◽  
Darboux Theorem ◽  
Noncommutative Spacetime ◽  
Emergent Spacetime ◽  
Planck Energy

A natural geometric framework of noncommutative spacetime is symplectic geometry rather than Riemannian geometry. The Darboux theorem in symplectic geometry then admits a novel form of the equivalence principle such that the electromagnetism in noncommutative spacetime can be regarded as a theory of gravity. Remarkably the emergent gravity reveals a noble picture about the origin of spacetime, dubbed as emergent spacetime, which is radically different from any previous physical theory all of which describe what happens in a given spacetime. In particular, the emergent gravity naturally explains the dynamical origin of flat spacetime, which is absent in Einstein gravity: A flat spacetime is not free gratis but a result of Planck energy condensation in a vacuum. This emergent spacetime picture, if it is correct anyway, turns out to be essential to resolve the cosmological constant problem, to understand the nature of dark energy and to explain why gravity is so weak compared to other forces.

scholarly journals Fine Structure of Dark Energy and New Physics

2007 ◽  
Vol 2007 ◽  
pp. 1-14 ◽  
Author(s):  
Vishnu Jejjala ◽  
Michael Kavic ◽  
Djordje Minic
Keyword(s):  
Fine Structure ◽  
Quantum Theory ◽  
Dark Energy ◽  
Cosmological Constant ◽  
New Physics ◽  
Blackbody Radiation ◽  
Cosmological Constant Problem ◽  
Radiation Problem ◽  
Specific Proposal ◽  
Dual Quantum

Following our recent work on the cosmological constant problem, in this letter we make a specific proposal regarding the fine structure (i.e., the spectrum) of dark energy. The proposal is motivated by a deep analogy between the blackbody radiation problem, which led to the development of quantum theory, and the cosmological constant problem, for which we have recently argued calls for a conceptual extension of the quantum theory. We argue that the fine structure of dark energy is governed by a Wien distribution, indicating its dual quantum and classical nature. We discuss observational consequences of such a picture of dark energy and constrain the distribution function.

scholarly journals Is the cosmological constant problem properly posed?

2017 ◽  
Vol 26 (12) ◽  
pp. 1743009 ◽  
Author(s):  
Philip D. Mannheim
Keyword(s):  
Cosmological Constant ◽  
Mechanical Energy ◽  
Zero Point ◽  
Black Body ◽  
Einstein Gravity ◽  
Momentum Tensor ◽  
Matrix Elements ◽  
Microwave Background ◽  
Cosmological Constant Problem ◽  
Quantum Mechanical Energy

In applications of Einstein gravity, one replaces the quantum-mechanical energy–momentum tensor of sources such as the degenerate electrons in a white dwarf or the black-body photons in the microwave background by c-number matrix elements. And not only that, one ignores the zero-point fluctuations in these sources by only retaining the normal-ordered parts of those matrix elements. There is no apparent justification for this procedure, and we show that it is precisely this procedure that leads to the cosmological constant problem. We suggest that solving the problem requires that gravity be treated just as quantum-mechanically as the sources to which it couples, and show that one can then solve the cosmological constant problem if one replaces Einstein gravity by the fully quantum-mechanically consistent conformal gravity theory.

scholarly journals Cosmological constant from the emergent gravity perspective

2014 ◽  
Vol 23 (06) ◽  
pp. 1430011 ◽  
Author(s):  
T. Padmanabhan ◽  
Hamsa Padmanabhan
Keyword(s):  
Cosmological Constant ◽  
Sufficient Conditions ◽  
Integration Constant ◽  
Dimensionless Number ◽  
Late Time ◽  
Field Equations ◽  
Cosmological Constant Problem ◽  
Emergent Gravity ◽  
Background Material ◽  
The Universe

Observations indicate that our universe is characterized by a late-time accelerating phase, possibly driven by a cosmological constant Λ, with the dimensionless parameter [Formula: see text], where LP= (Għ/c3)1/2is the Planck length. In this review, we describe how the emergent gravity paradigm provides a new insight and a possible solution to the cosmological constant problem. After reviewing the necessary background material, we identify the necessary and sufficient conditions for solving the cosmological constant problem. We show that these conditions are naturally satisfied in the emergent gravity paradigm in which (i) the field equations of gravity are invariant under the addition of a constant to the matter Lagrangian and (ii) the cosmological constant appears as an integration constant in the solution. The numerical value of this integration constant can be related to another dimensionless number (called CosMIn) that counts the number of modes inside a Hubble volume that cross the Hubble radius during the radiation and the matter-dominated epochs of the universe. The emergent gravity paradigm suggests that CosMIn has the numerical value 4π, which, in turn, leads to the correct, observed value of the cosmological constant. Further, the emergent gravity paradigm provides an alternative perspective on cosmology and interprets the expansion of the universe itself as a quest towards holographic equipartition. We discuss the implications of this novel and alternate description of cosmology.

DARK MATTER AND DARK ENERGY - FACT OR FANTASY?

2004 ◽  
Vol 19 (31) ◽  
pp. 5333-5333
Author(s):  
PHILIP MANNHEIM
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Constant ◽  
Particle Physics ◽  
Einstein Gravity ◽  
Fine Tuning ◽  
Accelerating Universe ◽  
Conformal Invariant ◽  
Invariant Metric ◽  
Conformal Theory

We show that the origin of the dark matter and dark energy problems originates in the assumption of standard Einstein gravity that Newton's constant is fundamental. We discuss an alternate, conformal invariant, metric theory of gravity in which Newton's constant is induced dynamically, with the global induced one which is effective for cosmology being altogether weaker than the local induced one needed for the solar system. We find that in the theory dark matter is no longer needed, and that the accelerating universe data can be fitted without fine-tuning using a cosmological constant as large as particle physics suggests. In the conformal theory then it is not the cosmological constant which is quenched but rather the amount of gravity that it produces.

scholarly journals Dark energy from gravitational corrections

2017 ◽  
Vol 32 (06n07) ◽  
pp. 1750037 ◽  
Author(s):  
Yugo Abe ◽  
Masaatsu Horikoshi ◽  
Yoshiharu Kawamura
Keyword(s):  
Field Theory ◽  
Dark Energy ◽  
Cosmological Constant ◽  
Effective Field Theory ◽  
Vacuum Energy ◽  
Effective Field ◽  
Microscopic Level ◽  
Cosmological Constant Problem ◽  
Gravitational Fields ◽  
Dominant Part

We study physics concerning the cosmological constant problem in the framework of effective field theory and suggest that a dominant part of dark energy can originate from gravitational corrections of vacuum energy, under the assumption that the classical gravitational fields do not couple to a large portion of the vacuum energy effectively, in spite of the coupling between graviton and matters at a microscopic level. Our speculation is excellent with terascale supersymmetry.

scholarly journals Predicting Planck Scale and Newtonian Constant from a Yang-Mills Gauge Theory: 1- and 2-Loop Estimates

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Rodrigo F. Sobreiro ◽  
Anderson A. Tomaz
Keyword(s):  
Gauge Theory ◽  
Cosmological Constant ◽  
Planck Scale ◽  
Cosmological Constant Problem ◽  
Emergent Gravity ◽  
Yang Mills ◽  
Dimensional Spacetime ◽  
Newtonian Constant

Recently, a model for an emergent gravity based onSO(5)Yang-Mills action in Euclidian 4-dimensional spacetime was proposed. In this work we provide some 1- and 2-loop computations and show that the model can accommodate suitable predicting values for the Newtonian constant. Moreover, it is shown that the typical scale of the expected transition between the quantum and the geometrodynamical theory is consistent with Planck scale. We also provide a discussion on the cosmological constant problem.

Induced dark energy in a warped braneworld and accelerating universe

2016 ◽  
Vol 25 (01) ◽  
pp. 1650004 ◽  
Author(s):  
Tae Hoon Lee
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Einstein Gravity ◽  
Accelerating Universe ◽  
External Space ◽  
Negative Cosmological Constant

In the six-dimensional (6D) Einstein gravity with a negative cosmological constant, we determine the structure of warped spacetimes bounded by 4-branes. We find an accelerating Universe solution with the induced dark energy, from the 4-brane obtained by orbifolding an external space, and suggest a possibility of addressing problems related to the cosmological constant.

scholarly journals Emergent spacetime for quantum gravity

2016 ◽  
Vol 25 (13) ◽  
pp. 1645010 ◽  
Author(s):  
Hyun Seok Yang
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Quantum Gravity ◽  
Theoretical Physics ◽  
Hierarchy Problem ◽  
Cosmological Constant Problem ◽  
Cosmic Inflation ◽  
Thought Patterns ◽  
Emergent Spacetime ◽  
New Perspective

We emphasize that noncommutative (NC) spacetime necessarily implies emergent spacetime if spacetime at microscopic scales should be viewed as NC. In order to understand NC spacetime correctly, we need to deactivate the thought patterns that we have installed in our brains and taken for granted for so many years. Emergent spacetime allows a background-independent formulation of quantum gravity that will open a new perspective to resolve the notorious problems in theoretical physics such as the cosmological constant problem, hierarchy problem, dark energy, dark matter and cosmic inflation.

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