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 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 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.

scholarly journals Quantization of emergent gravity

2015 ◽  
Vol 30 (04n05) ◽  
pp. 1550016 ◽  
Author(s):  
Hyun Seok Yang
Keyword(s):  
Gauge Theory ◽  
Quantum Gravity ◽  
Equivalence Principle ◽  
Symplectic Geometry ◽  
Symplectic Structure ◽  
Space Time ◽  
Quantization Scheme ◽  
Emergent Gravity ◽  
Darboux Theorem ◽  
Matter Fields

Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as space–time admits a symplectic structure, in other words, a microscopic space–time becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC space–time, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing space–time itself, leading to a dynamical NC space–time. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background-independent formulation where space–time and matter fields are equally emergent from a universal vacuum of quantum gravity.

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 Late-time cosmic acceleration: ABCD of dark energy and modified theories of gravity

2016 ◽  
Vol 25 (12) ◽  
pp. 1630031 ◽  
Author(s):  
M. Sami ◽  
R. Myrzakulov
Keyword(s):  
Dark Energy ◽  
Scalar Fields ◽  
Massive Gravity ◽  
Cosmic Acceleration ◽  
Modified Theories Of Gravity ◽  
Late Time ◽  
Cosmological Constant Problem ◽  
Chameleon Mechanism ◽  
Theories Of Gravity ◽  
Basic Ideas

We briefly review the problems and prospects of the standard lore of dark energy. We have shown that scalar fields, in principle, cannot address the cosmological constant problem. Indeed, a fundamental scalar field is faced with a similar problem dubbed naturalness. In order to keep the discussion pedagogical, aimed at a wider audience, we have avoided technical complications in several places and resorted to heuristic arguments based on physical perceptions. We presented underlying ideas of modified theories based upon chameleon mechanism and Vainshtein screening. We have given a lucid illustration of recently investigated ghost-free nonlinear massive gravity. Again, we have sacrificed rigor and confined to the basic ideas that led to the formulation of the theory. The review ends with a brief discussion on the difficulties of the theory applied to cosmology.

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.

scholarly journals Modified inertial mass from information loss

2017 ◽  
Vol 32 (28) ◽  
pp. 1750148 ◽  
Author(s):  
Michael E. McCulloch ◽  
Jaume Giné
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Inertial Mass ◽  
Information Loss ◽  
Cosmic Acceleration ◽  
Mass Energy ◽  
Cosmological Constant Problem ◽  
Hubble Horizon ◽  
Discrete Manner ◽  
Very High

A modification of inertia (called MiHsC or quantized inertia) has been proposed that assumes that inertia is caused by Unruh radiation, and that this radiation is made inhomogeneous in space by either Rindler horizons caused by acceleration or the distant Hubble horizon. The former predicts the standard inertial mass, and the latter predicts galaxy rotation without dark matter and cosmic acceleration without dark energy. It is proposed here that this model can be derived in an alternative way by assuming that the sum of mass (M), energy (E) and the information content of horizons (I) is conserved (EMI) so that mass–energy is released in a discrete manner when the area of a Rindler horizon reduces. This model could be tested by looking for the quantization of inertial mass and acceleration at very high accelerations, and may provide an explanation for the cosmological constant problem.

scholarly journals Geometry of Thermodynamic Processes

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 925 ◽  
Author(s):  
Arjan van der Schaft ◽  
Bernhard Maschke
Keyword(s):  
Symplectic Geometry ◽  
Hamiltonian Dynamics ◽  
Contact Geometry ◽  
Thermodynamic System ◽  
Lagrangian Submanifold ◽  
Geometric Framework ◽  
Definition Of ◽  
And Control ◽  
Geometric Formulation ◽  
Thermodynamic Processes

Since the 1970s, contact geometry has been recognized as an appropriate framework for the geometric formulation of thermodynamic systems, and in particular their state properties. More recently it has been shown how the symplectization of contact manifolds provides a new vantage point; enabling, among other things, to switch easily between the energy and entropy representations of a thermodynamic system. In the present paper, this is continued towards the global geometric definition of a degenerate Riemannian metric on the homogeneous Lagrangian submanifold describing the state properties, which is overarching the locally-defined metrics of Weinhold and Ruppeiner. Next, a geometric formulation is given of non-equilibrium thermodynamic processes, in terms of Hamiltonian dynamics defined by Hamiltonian functions that are homogeneous of degree one in the co-extensive variables and zero on the homogeneous Lagrangian submanifold. The correspondence between objects in contact geometry and their homogeneous counterparts in symplectic geometry, is extended to the definition of port-thermodynamic systems and the formulation of interconnection ports. The resulting geometric framework is illustrated on a number of simple examples, already indicating its potential for analysis and control.

scholarly journals A FIVE-DIMENSIONAL MODEL WITH A FIFTH DIMENSION AS FUNDAMENTAL AS TIME IN TERMS OF A COSMOLOGICAL APPROACH

2013 ◽  
Vol 28 (21) ◽  
pp. 1350095 ◽  
Author(s):  
GIZEM ŞENGÖR ◽  
METIN ARIK
Keyword(s):  
Dark Energy ◽  
The Other ◽  
Accelerated Expansion ◽  
Internal Space ◽  
Conformally Flat ◽  
Dimensional Model ◽  
Time Dimension ◽  
Flat Spacetime ◽  
Fifth Dimension ◽  
Five Dimensional Model

In five-dimensional cosmological models, the convention is to include the fifth dimension in a way similar to the other space dimensions. In this paper, we attempt to introduce the fifth dimension in a way that a time dimension would be introduced. With such an internal space, we are able to obtain accelerated expansion without introducing dark energy. We obtain a five-dimensional flat, meaning both Ricci flat and conformally flat, spacetime into which all relevant four-dimensional cosmologies can be locally embedded. We also argue on the choice of the cosmological frame. The choice that is simplest and most convenient in terms of dimensional analysis, amounts to a linearly expanding universe.

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