# Jun 30, 2019

As an undergraduate at Hampshire College, I did a lot of physics and some philosophy courses. Then when I went to Harvard for graduate school, I intended to do a double Ph.D. in physics and philosophy, but I got disenchanted with philosophy pretty quickly. I mean, the physicists were arrogant enough. But the philosophers even more so.

Lee Smolin in an interview with quanta magazine, explaining the sociology of physicists and philosophers.

# Mar 11, 2019

It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat.

Teddy Roosevelt

Excerpt from the speech “Citizenship In A Republic“, delivered at the Sorbonne, in Paris, France on 23 April, 1910.

# Dec 31, 2018

Gerard ‘t Hooft’s opinion [1] of causal sets, loop quantum gravity and causal dynamical triangulations as plausible approaches towards a theory of quantum gravity:

Numerous other schemes have been proposed, over time. As is often the case in situations such as these, there [has] been an abundance of completely wild concoctions that serious researchers have come up with. Lack of phantasy is not our problem [9][10][11].

where the references “[9][10][11]” are to the works [2, 3, 4, 5].

Warren Siegel in his text [6], commenting on the high energy levels required in order to be able to study String Theory:

Chapts. 2-5 can be considered almost as an independent book, an attempt at a general approach to all of field theory. For those few high energy physicists who are not intensely interested in strings (or do not have high enough energy to study them), it can be read as a new introduction to ordinary field theory, although familiarity with quantum field theory as it is usually taught is assumed.

# Dec 30, 2018

Joe Polchinski [7] on the significance of String Theory in the preface of Vol 1 of his magnum opus “String Theory“:

String theory (and the entire base of physics upon which it has been built) is one of mankind’s great achievements, and it has been my privilege to try to capture its current state.

# Dec 15, 2018

Peter Goddard [8] on the use of “modern” mathematics in theoretical high energy physics in the early days of string theory:

A senior and warmly admired physicist gave some lectures on the Regge theory of high energy processes. With great technical mastery, he was covering the board with special functions, doing manipulations that I knew from my studies with Alan White (who was also at the School) could be handled efficiently and elegantly using harmonic analysis on noncompact groups. Just as I was wondering whether it might be too impertinent to make a remark to this effect, the lecturer turned to the audience and said, “They tell me that you can do this all more easily if you use group theory, but I tell you that, if you are strong, you do not need group theory.

[1] G. t-Hooft, “Nature’s book keeping system,” Arxiv preprint arxiv:1605.00027, 2016.
[Bibtex]
@article{t-Hooft2016Natures,
Annote = {Wherein t'Hooft basically refers to LQG and associated
work as "completely wild concoctions" and "phantasy". When
such senior theorists dismiss LQG in this way, is it any
surprise that there exists a huge social gap between the
LQG and String communities?},
Author = {t-Hooft, Gerard},
Date-Modified = {2016-05-17 23:57:59 +0530},
Journal = {arXiv preprint arXiv:1605.00027},
Title = {Nature's Book Keeping System},
Year = {2016},
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[2] R. D. Sorkin, “Causal Sets: Discrete Gravity (Notes for the Valdivia Summer School),” Arxiv:gr-qc/0309009, 2003.
[Bibtex]
@article{Sorkin2003Causal,
Abstract = {These are lecture notes on causal set theory prepared in Jan. 2002 for a Summer School in Valdivia, Chile. In some places, they are more complete, in others much less so, regrettably. An extensive set of references and a glossary of terms can be found at the end of the notes.},
Archiveprefix = {arXiv},
Arxivid = {gr-qc/0309009},
Author = {Sorkin, Rafael D.},
Date-Modified = {2018-12-31 23:31:31 +0530},
Doi = {10.1007/0-387-24992-3_7},
Eprint = {0309009},
File = {:Users/deepak/ownCloud/root/research/mendeley/Sorkin{\_}Causal Sets Discrete Gravity (Notes for the Valdivia Summer School){\_}2003.pdf:pdf},
Isbn = {0-387-23995-2},
Issn = {{\textless}null{\textgreater}},
Journal = {arXiv:gr-qc/0309009},
Keywords = {Astrophysics,General Relativity and Quantum Cosmology,High Energy Physics - Theory},
Mendeley-Groups = {Zotero - Unifying Strings and Loops,Zotero - Zotero Library},
Mendeley-Tags = {Astrophysics,General Relativity and Quantum Cosmology,High Energy Physics - Theory},
Month = {sep},
Primaryclass = {gr-qc},
Shorttitle = {Causal Sets},
Title = {{Causal Sets: Discrete Gravity (Notes for the Valdivia Summer School)}},
Url = {http://arxiv.org/abs/gr-qc/0309009},
Year = {2003},
Bdsk-Url-1 = {http://arxiv.org/abs/gr-qc/0309009},
Bdsk-Url-2 = {https://doi.org/10.1007/0-387-24992-3_7}}
[3] C. Rovelli, Loop Quantum Gravity, 1997.
[Bibtex]
@misc{Rovelli1997Loop,
Abstract = {The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. The research in loop quantum gravity forms today a vast area, ranging from mathematical foundations to physical applications. Among the most significative results obtained are: (i) The computation of the physical spectra of geometrical quantities such as area and volume; which yields quantitative predictions on Planck-scale physics. (ii) A derivation of the Bekenstein-Hawking black hole entropy formula. (iii) An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime foam''. Long standing open problems within the approach (lack of a scalar product, overcompleteness of the loop basis, implementation of reality conditions) have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.},
Author = {Carlo Rovelli},
Comments = {Review paper written for the electronic journal Living Reviews'. 34 pages},
Date-Modified = {2019-01-01 00:15:31 +0530},
Doi = {10.12942/lrr-1998-1},
Eprint = {arXiv:gr-qc/9710008},
Howpublished = {LivingRev.Rel.1:1,1998},
Title = {{L}oop {Q}uantum {G}ravity},
Url = {http://arxiv.org/abs/gr-qc/9710008},
Year = {1997},
Bdsk-Url-1 = {http://arxiv.org/abs/gr-qc/9710008},
Bdsk-Url-2 = {https://doi.org/10.12942/lrr-1998-1}}
[4] L. Smolin, Three roads to quantum gravity, 2017 edition ed., New York: Basic books, 2017.
[Bibtex]
@book{Smolin2017Three,
Abstract = {"It is a search for a view of the universe that unites two seemingly opposed pillars of modern science: Einstein's theory of general relativity, which deals with large scale phenomena like planets, solar systems and galaxies, and quantum theory, which deals with the world of the very small -- molecules, atoms and electrons. In the last few years, physicists have made big steps toward their goal of a completely new theory of space, time and the universe, a "theory of everything." In Three Roads to Quantum Gravity, Lee Smolin, who has spent his career at the forefront of these new discoveries, presents the main ideas behind the new developments that have brought a quantum theory of gravity in sight. He explains in simple terms what scientists are talking about when they say the world is made from exotic entities such as loops, strings and black holes. As he does so, he tells the stories behind these discoveries: the rivalries, epiphanies and intrigues he witnessed first hand."--},
Annote = {LDR 02781cam 22004577i 4500
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},
Author = {Smolin, Lee},
Call-Number = {QC178},
Date-Modified = {2019-01-01 00:17:13 +0530},
Edition = {2017 edition},
Genre = {Quantum gravity},
Isbn = {9780465094547},
Library-Id = {2017448734},
Publisher = {Basic Books},
Title = {Three roads to quantum gravity},
Year = {2017}}
[5] J. Ambjorn, A. Goerlich, J. Jurkiewicz, and R. Loll, Quantum gravity via causal dynamical triangulations, 2013.
[Bibtex]
@misc{Ambjorn2013Quantum,
Abstract = {"Causal Dynamical Triangulations" ({CDT}) represent a
lattice regularization of the sum over spacetime histories,
providing us with a non-perturbative formulation of quantum
gravity. The ultraviolet fixed points of the lattice theory
can be used to define a continuum quantum field theory,
potentially making contact with quantum gravity defined via
asymptotic safety. We describe the formalism of {CDT}, its
phase diagram, and the quantum geometries emerging from it.
We also argue that the formalism should be able to describe
a more general class of quantum-gravitational models of
{Horava-Lifshitz} type.},
Archiveprefix = {arXiv},
Author = {Ambjorn, J. and Goerlich, A. and Jurkiewicz, J. and Loll, R.},
Citeulike-Article-Id = {12015297},
Date-Modified = {2013-12-05 18:47:23 +0530},
Day = {8},
Eprint = {1302.2173},
Keywords = {asymptotic\_safety, b\_dittrich, causal\_dynamical\_triangulations, fixed\_point, gorlich\_a, horava\_lifshitz, jurkiewicz\_j, lattice\_models, manybody, non-perturbative, phase\_transition, quantum\_gravity, renate\_loll},
Month = feb,
Posted-At = {2013-12-05 13:11:27},
Priority = {2},
Title = {Quantum Gravity via Causal Dynamical Triangulations},
Url = {http://arxiv.org/abs/1302.2173},
Year = {2013},
Bdsk-Url-1 = {http://arxiv.org/abs/1302.2173}}
[6] W. Siegel, “Introduction to string field theory,” , 2001.
[Bibtex]
@article{Siegel2001Introduction,
Abstract = {The 1988 book, now free, with corrections and bookmarks
(for pdf).},
Archiveprefix = {arXiv},
Arxivid = {hep-th/0107094},
Author = {Siegel, W.},
Date-Modified = {2018-12-07 18:44:25 +0530},
Doi = {10.1016/0550-3213(93)90388-6},
Eprint = {0107094},
File = {:Users/deepak/mendeley/Siegel{\_}Trimeric mechanism of proton transfer in imidazole{\_}2002.pdf:pdf},
Mendeley-Groups = {Unifying Strings and Loops},
Month = {jul},
Primaryclass = {hep-th},
Title = {{Introduction to string field theory}},
Url = {http://arxiv.org/abs/hep-th/0107094 http://dx.doi.org/10.1016/0550-3213(93)90388-6},
Year = {2001},
Bdsk-Url-1 = {http://arxiv.org/abs/hep-th/0107094%20http://dx.doi.org/10.1016/0550-3213(93)90388-6},
Bdsk-Url-2 = {https://doi.org/10.1016/0550-3213(93)90388-6}}
[7] J. Polchinski, String theory (cambridge monographs on mathematical physics) (volume 1), 1 ed., Cambridge university press, 1998.
[Bibtex]
@book{Polchinski1998aString,
Author = {Polchinski, Joseph},
Citeulike-Article-Id = {9043910},
Date-Modified = {2012-08-22 19:46:06 +0530},
Day = {13},
Edition = {1},
Howpublished = {Hardcover},
Isbn = {9780521633031},
Keywords = {book, introduction, mathematical\_physics, polchinski, string\_theory},
Month = oct,
Posted-At = {2011-03-22 19:38:04},
Priority = {2},
Publisher = {Cambridge University Press},
Title = {String Theory (Cambridge Monographs on Mathematical Physics) (Volume 1)},
Url = {http://www.amazon.com/exec/obidos/redirect?tag=citeulike07-20\&path=ASIN/0521633036},
Year = {1998},
Bdsk-Url-1 = {http://www.amazon.com/exec/obidos/redirect?tag=citeulike07-20%5C&path=ASIN/0521633036}}
[8] P. Goddard, “From Dual Models to String Theory,” , 2008.
[Bibtex]
@article{Goddard2008From,
Abstract = {A personal view is given of the development of string
theory out of dual models, including the analysis of the
structure of the physical states and the proof of the
No-Ghost Theorem, the quantization of the relativistic
string, and the calculation of fermion-fermion
scattering.},
Archiveprefix = {arXiv},
Arxivid = {0802.3249},
Author = {Goddard, Peter},
Bdsk-Url-1 = {http://arxiv.org/abs/0802.3249}}`