Sunday, May 29, 2011

Ramakrishna


Minus the celibacy thing (to each their own) I totally love this guy. The West has damed little knowledge of India, but THIS was one of the greatest men of all time. 

Ramakrishna (Bengali: রামকৃষ্ণ পরমহংস Ramkṛiṣṇo Pôromôhongśo) (February 18, 1836 – August 16, 1886), born Gadadhar Chattopadhyay[2] (Bengali: গদাধর চট্টোপাধ্যায় Gôdadhor Chôţţopaddhae), was a famous mystic of 19th-century India.[3] His religious school of thought led to the formation of the Ramakrishna Mission by his chief disciple Vivekananda[4][5][6][7] – both were influential figures in theBengali Renaissance[8] as well as the Hindu renaissance during the 19th and 20th centuries.[9][10][11] Many of his disciples and devotees believe he was an Avatar or incarnation of God.[12] He is also referred as "Paramahamsa" by his devotees, as such he is popularly known as Ramkrishna Paramhansa.
Ramakrishna was born in a poor Brahmin Vaishnava family in rural Bengal. He became a priest of the Dakshineswar Kali Temple, dedicated to the goddess Kali, which had the influence of the main strands of Bengali bhakti tradition.[2] His first spiritual teacher was an ascetic woman skilled in Tantra and Vaishnava bhakti.[13] Later an Advaita Vedantin ascetic taught him non-dual meditation, and according to Ramakrishna, he experienced nirvikalpa samadhi under his guidance. Ramakrishna also experimented with other religions, notably Islam and Christianity, and said that they all lead to the same God.[2] Though conventionally uneducated, he attracted the attention of the middle class and numerous Bengali intellectuals.[citation needed]

Contents

 [hide]
Posted by at 2 comments:

Saturday, May 28, 2011

Entropic Gravity


Eric Verlinde


Verlinde's statistical description of gravity as an entropic force leads to the correct inverse square distance law of attraction between classical bodies.

Entropic gravity is a hypothesis in modern physics that describes gravity as an entropic force; not a fundamental interaction mediated by a particle, but a probabilistic consequence of physical systems' tendency to increase their entropy.

Origin

The probabilistic description of gravity has a history that goes back at least to Richard Feynman in the early 1960's,[1] and to research on black hole thermodynamics by Bekenstein and Hawking in the mid-1970s. These studies suggest a deep connection between gravity and thermodynamics, which describes the behavior of heat and gases. In 1995, Jacobson demonstrated that the Einstein equations describing relativistic gravitation can be derived by combining general thermodynamic considerations with the equivalence principle.[2] Subsequently, other physicists began to explore links between gravity and entropy.[3][4]

Erik Verlinde's theory

In 2009, Erik Verlinde disclosed a conceptual theory that describes gravity as an entropic force.[5] On January 6, 2010 he published a preprint of a 29 page paper titled On the Origin of Gravity and the Laws of Newton.[6] (It was published in April 2011).[7] Reversing the logic of over 300 years, it argued that gravity is a consequence of the laws of thermodynamics. This theory combines the thermodynamic approach to gravity with Gerardus 't Hooft's holographic principle. If proven correct, this implies gravity is not a fundamental interaction, but anemergent phenomenon which arises from the statistical behavior of microscopic degrees of freedom encoded on a holographic screen. The paper drew a variety of responses from the scientific community. Andrew Strominger, a string theorist at Harvard said “Some people have said it can’t be right, others that it’s right and we already knew it — that it’s right and profound, right and trivial."[8]
Verlinde's article also attracted a large amount of media exposure,[9][10] and led to immediate follow-up work in cosmology,[11][12] the dark energy hypothesis,[13] cosmological acceleration,[14][15] cosmological inflation,[16] and loop quantum gravity.[17] Also, a specific microscopic model has been proposed that indeed leads to entropic gravity emerging at large scales.[18]


Critique

Verlinde’s theory is criticized [19] on the basis that it fails to reproduce gravitational bound states of neutron observed in the experiments with ultracold neutrons[20]


See also


References

  1. ^ R.P. Feynman, The Character of Physical Law (Messenger Lectures, 1964): Lecture 2 on The Relation of Mathematics to Physics; Feynman's attempt at a statistical description of gravity starts 7 minutes into this video clip
  2. ^ Jacobson, Theodore (4 April 1995). "Thermodynamics of Spacetime: The Einstein Equation of State". Phys.Rev.Lett.75:1260-1263,1995 75 (7): 1260–1263. arXiv:gr-qc/9504004.Bibcode 1995PhRvL..75.1260J. doi:10.1103/PhysRevLett.75.1260.
  3. ^ Padmanabhan, Thanu (26 November 2009). "Thermodynamical Aspects of Gravity: New insights". Rep. Prog. Phys. 73 (2010)01 73 (4): 6901. arXiv:0911.5004. Bibcode2010RPPh...73d6901P. doi:10.1088/0034-4885/73/4/046901.
  4. ^ Mok, H.M. (13 August 2004). "Further Explanation to the Cosmological Constant Problem by Discrete Space-time Through Modified Holographic Principle".arXiv:physics/0408060 [physics.gen-ph].
  5. ^ van Calmthout, Martijn (12 December 2009). "Is Einstein een beetje achterhaald?" (in Dutch). de Volkskrant. Retrieved 6 September 2010.
  6. ^ Verlinde, Eric (6 January 2010). "Title: On the Origin of Gravity and the Laws of Newton". arXiv:1001.0785 [hep-th].
  7. ^ E.P. Verlinde. "On the Origin of Gravity and the Laws of Newton". JHEP 04, 29 (2011). doi:10.1007/JHEP04(2011)029.
  8. ^ Overbye, Dennis (July 12, 2010). "A Scientist Takes On Gravity". The New York Times. Retrieved 6 September 2010.
  9. ^ The entropy force: a new direction for gravity, New Scientist, 20 January 2010, issue 2744
  10. ^ Gravity is an entropic form of holographic information, Wired Magazine, 20 January 2010
  11. ^ Fu-Wen Shu; Yungui Gong (2010). "Equipartition of energy and the first law of thermodynamics at the apparent horizon". arXiv:1001.3237 [gr-qc].
  12. ^ Rong-Gen Cai; Li-Ming Cao; Nobuyoshi Ohta (2010). "Friedmann Equations from Entropic Force". Phys. Rev. D 8101(R) (2010) 81 (6). arXiv:1001.3470. Bibcode2010PhRvD..81f1501C. doi:10.1103/PhysRevD.81.061501.
  13. ^ It from Bit: How to get rid of dark energy, Johannes Koelman, 2010
  14. ^ Easson; Frampton; Smoot (2010). "Entropic Accelerating Universe". Phys.Lett.B696:273-277,2011 696 (3): 273–277. arXiv:1002.4278. Bibcode 2011PhLB..696..273E.doi:10.1016/j.physletb.2010.12.025.
  15. ^ Yi-Fu Cai; Jie Liu; Hong Li (2010). "Entropic cosmology: a unified model of inflation and late-time acceleration". Phys.Lett.B 690:213-219,2010 690 (3): 213–219. arXiv:1003.4526.Bibcode 2010PhLB..690..213C. doi:10.1016/j.physletb.2010.05.033.
  16. ^ Yi Wang (2010). "Towards a Holographic Description of Inflation and Generation of Fluctuations from Thermodynamics". arXiv:1001.4786 [hep-th].
  17. ^ Lee Smolin (2010). "Newtonian gravity in loop quantum gravity". arXiv:1001.3668 [gr-qc].
  18. ^ Jarmo Mäkelä (2010). "Notes Concerning "On the Origin of Gravity and the Laws of Newton" by E. Verlinde (arXiv:1001.0785)". arXiv:1001.3808 [gr-qc].
  19. ^ Kobakhidze, Archil (15 January 2011). "Gravity is not an entropic force". Phys. Rev. D83: 021502,2011 83 (2): 021502(3 pages). arXiv:[hep-th arXiv:1009.5414 [hep-th]]. Bibcode2011PhRvD..83b1502K. doi:10.1103/PhysRevD.83.021502.
  20. ^ Nesvizhevsky, V.V., et al. (17 January 2002). "Quantum states of neutrons in the Earth's gravitational field". Nature 415: 297-299. Bibcode 2002Natur.415..297N.doi:10.1038/415297a.

]Further reading

Posted by at 9 comments:
Subscribe to: Posts (Atom)