Play Video
1
Roger Penrose - Cyclic Universe Model
Roger Penrose - Cyclic Universe Model
::2007/04/29::
Play Video
2
Cyclic Universe
Cyclic Universe
::2010/12/07::
Play Video
3
Cyclic Model proves Hinduism
Cyclic Model proves Hinduism's concept of the Universe H H Swami Sathyananda Saraswathi Tiruvadikal
::2011/08/11::
Play Video
4
The Cyclic Ekpyrotic Model
The Cyclic Ekpyrotic Model
::2010/06/21::
Play Video
5
Roger Penrose - Modelo de Universo Cíclico (Cyclic Universe Model)
Roger Penrose - Modelo de Universo Cíclico (Cyclic Universe Model)
::2010/04/21::
Play Video
6
Creative Cyclic Model in playful 3-D
Creative Cyclic Model in playful 3-D
::2012/09/23::
Play Video
7
Creative Cyclic Model in playful 3-D [alt view]
Creative Cyclic Model in playful 3-D [alt view]
::2012/09/23::
Play Video
8
Business Model Innovation
Business Model Innovation
::2013/10/22::
Play Video
9
reinforced concrete shear wall ANSYS cyclic loading
reinforced concrete shear wall ANSYS cyclic loading
::2013/04/12::
Play Video
10
Before the big bang 2 - Conformal Cyclic Cosmology explained
Before the big bang 2 - Conformal Cyclic Cosmology explained
::2014/01/24::
Play Video
11
What is Business Model Innovation?
What is Business Model Innovation?
::2012/09/22::
Play Video
12
Qlikview Basic Tutorial -  Hierarchies Cyclic Grouping - Free Training Part-6-of-40
Qlikview Basic Tutorial - Hierarchies Cyclic Grouping - Free Training Part-6-of-40
::2013/11/27::
Play Video
13
Notched beam under cyclic loading
Notched beam under cyclic loading
::2009/01/23::
Play Video
14
Increasing Mass Transfer Efficiency in Distillation Tray by Cyclic Distillation
Increasing Mass Transfer Efficiency in Distillation Tray by Cyclic Distillation
::2014/06/03::
Play Video
15
CYCLIC-OSCILATING-REBOUNDING-UNIVERSE
CYCLIC-OSCILATING-REBOUNDING-UNIVERSE
::2011/04/19::
Play Video
16
Analysis of a RC wall failing in shear under cyclic loading
Analysis of a RC wall failing in shear under cyclic loading
::2013/11/25::
Play Video
17
Learn How To Fly RC Helicopter (LEARNING CYCLIC CONTROLS)
Learn How To Fly RC Helicopter (LEARNING CYCLIC CONTROLS)
::2009/05/22::
Play Video
18
RC Cantilever Under Cyclic Load in Abaqus
RC Cantilever Under Cyclic Load in Abaqus
::2014/06/30::
Play Video
19
Emergent behaviour - 10,000,000 agents - butterfly cyclic migration
Emergent behaviour - 10,000,000 agents - butterfly cyclic migration
::2011/05/05::
Play Video
20
Inflationary cosmology on trial
Inflationary cosmology on trial
::2011/04/04::
Play Video
21
Mod-01 Lec-29 OFDM Schematic and Cyclic Prefix
Mod-01 Lec-29 OFDM Schematic and Cyclic Prefix
::2013/06/11::
Play Video
22
Proof Cyclic Quadrilaterals
Proof Cyclic Quadrilaterals
::2013/02/14::
Play Video
23
Time series (TCSI)  Model using Excel
Time series (TCSI) Model using Excel
::2012/05/27::
Play Video
24
Cyclic NonCyclic Photophosphorylation
Cyclic NonCyclic Photophosphorylation
::2012/09/06::
Play Video
25
Two Paul Steinhardt Projects: "Cyclic Universe" and "Quasicrystals"
Two Paul Steinhardt Projects: "Cyclic Universe" and "Quasicrystals"
::2013/05/07::
Play Video
26
Cyclic Symmetry
Cyclic Symmetry
::2014/03/11::
Play Video
27
Cyclic Voltammetry of Ferricyanide solution using KCl as supporting electrolyte.
Cyclic Voltammetry of Ferricyanide solution using KCl as supporting electrolyte.
::2011/08/14::
Play Video
28
Cantilevered Column Test
Cantilevered Column Test
::2008/07/02::
Play Video
29
Inverse Kinematics using Cyclic-Coordinate Descent
Inverse Kinematics using Cyclic-Coordinate Descent
::2008/08/01::
Play Video
30
Dark Matter ; the Undetectable Mass
Dark Matter ; the Undetectable Mass
::2013/12/11::
Play Video
31
Cyclic and Noncyclic Photophosphorylation [HD Animation]
Cyclic and Noncyclic Photophosphorylation [HD Animation]
::2014/03/05::
Play Video
32
CYCLIC PITCH & SWASH PLATE
CYCLIC PITCH & SWASH PLATE
::2008/08/10::
Play Video
33
Inscribed Angles in Cyclic Quadrilaterals
Inscribed Angles in Cyclic Quadrilaterals
::2012/12/29::
Play Video
34
Cyclic crack propagation/closure problem with frictional slip
Cyclic crack propagation/closure problem with frictional slip
::2013/11/02::
Play Video
35
Contact Cyclic Load in Abaqus
Contact Cyclic Load in Abaqus
::2014/06/30::
Play Video
36
Naming Cycloalkanes and Bicyclo Alkanes
Naming Cycloalkanes and Bicyclo Alkanes
::2013/02/24::
Play Video
37
Obergman — Cyclic Multiverse
Obergman — Cyclic Multiverse
::2014/05/22::
Play Video
38
Cyclic Bend Test Equipment for JEDEC JESD22B113
Cyclic Bend Test Equipment for JEDEC JESD22B113
::2012/12/04::
Play Video
39
Multiverse: One Universe or Many - World Science Festival 2013
Multiverse: One Universe or Many - World Science Festival 2013
::2013/06/15::
Play Video
40
Twisted File vs. ProTaper Cyclic Fatigue Test - Dr. Tomas Lang
Twisted File vs. ProTaper Cyclic Fatigue Test - Dr. Tomas Lang
::2012/06/08::
Play Video
41
Cyclic symmetry in LISA
Cyclic symmetry in LISA
::2013/06/21::
Play Video
42
Circle Properties (Inscribed and Central angles, Cyclic Quadrilateral, etc)
Circle Properties (Inscribed and Central angles, Cyclic Quadrilateral, etc)
::2012/05/07::
Play Video
43
Cyclic Universe "Part
Cyclic Universe "Part '2" - (A Beginning and an End)
::2013/07/22::
Play Video
44
600WHP Subaru Impreza STi   Anti Lag and Cyclic Idle in Car Demo ! ByKayseri !
600WHP Subaru Impreza STi Anti Lag and Cyclic Idle in Car Demo ! ByKayseri !
::2014/05/11::
Play Video
45
TT Raptor E550FBL Cyclic Servos and Head Setup
TT Raptor E550FBL Cyclic Servos and Head Setup
::2014/03/21::
Play Video
46
Learn How To Fly RC Helicopter (HOVERING - Rudder & Cyclic - tail in orientation)
Learn How To Fly RC Helicopter (HOVERING - Rudder & Cyclic - tail in orientation)
::2009/06/17::
Play Video
47
Model helicopter controlled by PS3 SIXAXIS
Model helicopter controlled by PS3 SIXAXIS
::2007/07/30::
Play Video
48
Helicopter Main Rotor: Collective / Cyclic - Rotor Principal Helicóptero: Coletivo / Cíclico
Helicopter Main Rotor: Collective / Cyclic - Rotor Principal Helicóptero: Coletivo / Cíclico
::2012/09/27::
Play Video
49
Cyclic Cellular Automata 3D
Cyclic Cellular Automata 3D
::2013/08/28::
Play Video
50
Preview - The Cyclic Universe - A conversation with Roger Penrose
Preview - The Cyclic Universe - A conversation with Roger Penrose
::2013/07/04::
NEXT >>
RESULTS [51 .. 101]
From Wikipedia, the free encyclopedia
Jump to: navigation, search

A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 theorized a universe following an eternal series of oscillations, each beginning with a big bang and ending with a big crunch; in the interim, the universe would expand for a period of time before the gravitational attraction of matter causes it to collapse back in and undergo a bounce.

Overview[edit]

In the 1920s, theoretical physicists, most notably Albert Einstein, considered the possibility of a cyclic model for the universe as an (everlasting) alternative to the model of an expanding universe. However, work by Richard C. Tolman in 1934 showed that these early attempts failed because of the cyclic problem: according to the Second Law of Thermodynamics, entropy can only increase.[1] This implies that successive cycles grow longer and larger. Extrapolating back in time, cycles before the present one become shorter and smaller culminating again in a Big Bang and thus not replacing it. This puzzling situation remained for many decades until the early 21st century when the recently discovered dark energy component provided new hope for a consistent cyclic cosmology.[2] In 2011, a five-year survey of 200,000 galaxies and spanning 7 billion years of cosmic time confirmed that "dark energy is driving our universe apart at accelerating speeds."[3][4]

One new cyclic model is a brane cosmology model of the creation of the universe, derived from the earlier ekpyrotic model. It was proposed in 2001 by Paul Steinhardt of Princeton University and Neil Turok of Cambridge University. The theory describes a universe exploding into existence not just once, but repeatedly over time.[5][6] The theory could potentially explain why a mysterious, repulsive form of energy known as the cosmological constant, which is accelerating the expansion of the universe, is several orders of magnitude smaller than predicted by the standard Big Bang model.

A different cyclic model relying on the notion of phantom energy was proposed in 2007 by Lauris Baum and Paul Frampton of the University of North Carolina at Chapel Hill.[7]

Other cyclic models include Conformal cyclic cosmology and Loop quantum cosmology.

The Steinhardt–Turok model[edit]

In this cyclic model, two parallel orbifold planes or M-branes collide periodically in a higher-dimensional space.[8] The visible four-dimensional universe lies on one of these branes. The collisions correspond to a reversal from contraction to expansion, or a big crunch followed immediately by a big bang. The matter and radiation we see today were generated during the most recent collision in a pattern dictated by quantum fluctuations created before the branes. After billions of years the universe reached the state we observe today; after additional billions of years it will ultimately begin to contract again. Dark energy corresponds to a force between the branes, and serves the crucial role of solving the monopole, horizon, and flatness problems. Moreover the cycles can continue indefinitely into the past and the future, and the solution is an attractor, so it can provide a complete history of the universe.

As Richard C. Tolman showed, the earlier cyclic model failed because the universe would undergo inevitable thermodynamic heat death.[1] However, the newer cyclic model evades this by having a net expansion each cycle, preventing entropy from building up. However, there remain major open issues in the model. Foremost among them is that colliding branes are not understood by string theorists, and nobody knows if the scale invariant spectrum will be destroyed by the big crunch. Moreover, as with cosmic inflation, while the general character of the forces (in the ekpyrotic scenario, a force between branes) required to create the vacuum fluctuations is known, there is no candidate from particle physics. [9]

The Baum–Frampton model[edit]

This more recent cyclic model of 2007 makes a different technical assumption concerning the equation of state of the dark energy which relates pressure and density through a parameter w.[7][10] It assumes w < −1 (a condition called phantom energy) throughout a cycle, including at present. (By contrast, Steinhardt–Turok assume w is never less than −1.) In the Baum–Frampton model, a septillionth (or less) of a second before the would-be Big Rip, a turnaround occurs and only one causal patch is retained as our universe. The generic patch contains no quark, lepton or force carrier; only dark energy – and its entropy thereby vanishes. The adiabatic process of contraction of this much smaller universe takes place with constant vanishing entropy and with no matter including no black holes which disintegrated before turnaround.

The idea that the universe "comes back empty" is a central new idea of this cyclic model, and avoids many difficulties confronting matter in a contracting phase such as excessive structure formation, proliferation and expansion of black holes, as well as going through phase transitions such as those of QCD and electroweak symmetry restoration. Any of these would tend strongly to produce an unwanted premature bounce, simply to avoid violation of the second law of thermodynamics. The surprising w < −1 condition may be logically inevitable in a truly infinitely cyclic cosmology because of the entropy problem. Nevertheless, many technical back up calculations are necessary to confirm consistency of the approach. Although the model borrows ideas from string theory, it is not necessarily committed to strings, or to higher dimensions, yet such speculative devices may provide the most expeditious methods to investigate the internal consistency. The value of w in the Baum–Frampton model can be made arbitrarily close to, but must be less than, −1.

Other cyclic models[edit]

  • Conformal cyclic cosmology - a general relativity based theory due to Roger Penrose in which the universe expands until all the matter decays and is turned to light - so there is nothing in the universe that has any time or distance scale associated with it. This permits it to become identical with the Big Bang, so starting the next cycle.
  • Loop quantum cosmology which predicts a "quantum bridge" between contracting and expanding cosmological branches.

See also[edit]

Physical cosmologies:

Religion:

Notes[edit]

  1. ^ a b R.C. Tolman (1987) [1934]. Relativity, Thermodynamics, and Cosmology. New York: Dover. ISBN 0-486-65383-8. LCCN 34032023. 
  2. ^ P.H. Frampton (2006). "On Cyclic Universes". arXiv:astro-ph/0612243 [astro-ph].
  3. ^ Dark Energy Is Driving Universe Apart: NASA's Galaxy Evolution Explorer Finds Dark Energy Repulsive
  4. ^ The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts
  5. ^ P.J. Steinhardt, N. Turok (2001). "Cosmic Evolution in a Cyclic Universe". Phys. Rev. D 65 (12). arXiv:hep-th/0111098. Bibcode:2002PhRvD..65l6003S. doi:10.1103/PhysRevD.65.126003. 
  6. ^ P.J. Steinhardt, N. Turok (2001). "A Cyclic Model of the Universe". Science 296 (5572): 1436–1439. arXiv:hep-th/0111030. Bibcode:2002Sci...296.1436S. doi:10.1126/science.1070462. PMID 11976408. 
  7. ^ a b L. Baum, P.H. Frampton (2007). "Entropy of Contracting Universe in Cyclic Cosmology". Mod.Phys.Lett.A 23: 33. arXiv:hep-th/0703162. Bibcode:2008MPLA...23...33B. doi:10.1142/S0217732308026170. 
  8. ^ P.J. Steinhardt, N. Turok (2004). "The Cyclic Model Simplified". New Astron.Rev. 49 (2–6): 43–57. arXiv:astro-ph/0404480. Bibcode:2005NewAR..49...43S. doi:10.1016/j.newar.2005.01.003. 
  9. ^ P. Woit (2006). Not Even Wrong. London: Random House. ISBN 978-0-09-948864-4. 
  10. ^ L. Baum and P.H. Frampton (2007). "Turnaround in Cyclic Cosmology". Physical Review Letters 98 (7): 071301. arXiv:hep-th/0610213. Bibcode:2007PhRvL..98g1301B. doi:10.1103/PhysRevLett.98.071301. PMID 17359014. 

Further reading[edit]

External links[edit]

Wikipedia content is licensed under the GFDL License
Powered by YouTube
LEGAL
  • Mashpedia © 2014