Monday, 12Oct2015 11:50:19 EDT
RESUMÉ: Warren Siegel
RESEARCH: Highenergy theoretical physics
"MAJOR" PUBLICATIONS (see also "The Free Library" below):
 Simplifying algebra in Feynman graphs, part II: Spinor helicity
from the spacecone,
hepph/9801220,
Phys.Rev.D59(1999)045013 (with G. Chalmers)
 new, easiest way to do QCD graphs; derives & simplifies "spinor helicity"
 Superspace duality in lowenergy superstrings,
hepth/9305073,
Phys.Rev.D48(1993)2826
 invention of socalled "double field theory"
 Gauge string fields from the light cone,
Nucl.Phys.B282(1987)125 (with B. Zwiebach)
 free gaugeinvariant actions for any theory in any dimension
 Covariantly secondquantized string II, Phys.Lett.149B(1984)157,
151B(1985)391
 invention of (covariant) string field theory
 Manifest Lorentz invariance sometimes requires nonlinearity,
Nucl.Phys.B238(1984)307
 chiral bosons
 Hidden local supersymmetry in the supersymmetric particle
action, Phys.Lett.128B(1983)397
 "kappa" symmetry
 Supergraphity (II).
Manifestly covariant rules and higher loop finiteness,
Nucl.Phys.B201(1982)292 (with M.T. Grisaru)
 power counting for extended supersymmetry
(later used for finiteness proof for N=4)
 Improved methods for supergraphs, Nucl.Phys.B159(1979)429,
(with M.T. Grisaru and M. Roček)
 Unextended superfields in extended supersymmetry,
Nucl.Phys.B156(1979)135
 ChernSimons terms in actions
 Supersymmetric dimensional
regularization via dimensional reduction, Phys.Lett.84B(1979)193
CURRENT RESEARCH
My main interest is confinement. It's the least understood ingredient of the Standard Model. It's the key to understanding the strong interactions. It might even be the key to understanding quantum gravity.
Confinement is a longdistance effect ("infrared slavery"). The leading infrared behavior of Quantum ChromoDynamics (or any theory containing massless YangMills) is the same as that of N=4 supersymmetric YangMills. The Smatrices in this theory are simpler than those of any other theory based on YangMills, including the Standard Model.
My goals are:
 to find better ways to calculate field theory Smatrices (including the incorporation of Yangian symmetry), and
 to find string formulations of YangMills theories that produce Smatrices resembling those for hadrons in the real world (and thus understand confinement).
Some useful interrelated methods are:
 Projective superspace is a subspace of the full superspace (like chiral superspace, but real) that is the only successful method for describing 4D N=2 supersymmetric theories in a manifestly supersymmetric (& conformally supersymmetric) way. Some of my research involves generalizing these results
 to be more useful @ the quantum level (with Jain), as we did for N=1 (with Grisaru & Roček);
 to N=4 (with Hatsuda);
 to firstquantization (with Hatsuda & Y.t. Huang).

The AdS/CFT correspondence allows strings to bring light on 4D quantum field theory, and vice versa. I'm focusing in particular on Smatrices, corresponding to closed strings with worldsheet boundaries coinciding with the boundary of antide Sitter space, corresponding to evaluating correlation functions of gauge singlets (each a loop of the boundary) or Smatrices of fundamental fields (all forming a single loop, as a single color trace). I'm looking at various superspace approaches and their relations to first and secondquantization of particles (with Dai, Hatsuda, R.N. Huang, Nastase, & Roiban).
 The spacecone gauge explains and gives a simpler form of the "spinor helicity" rules that make Smatrix calculations in YangMills tractable (work with Chalmers). It has an especially interesting interpretation on AdS₅×S⁵: After Wick rotating the sphere to resemble AdS, the spacelike bulk coordinates of each can be combined to form the complex, null coordinates that define spacecone quantization. The surviving superspace coordinates are then just these 2 coordinates and those of 4D N=4 projective superspace.
PAST RESEARCH AT STONY BROOK
Selfduality & conformal invariance
I found that all free conformal theories contain only selfdual or antiselfdual states.
I showed that a string thought to be inconsistent in
positive dimensions ("N=4") was actually a more symmetric formulation of a
consistent string theory ("N=2") known to describe selfdual theories.
Chalmers and I showed that selfdual theories can be used as the lowest
order in a perturbative helicity expansion in theories such as QCD,
and developed spacecone gauge quantization to explain, systematize, and further
simplify spinor helicity methods in QCD.
Dennen, Y. Huang, & I applied supertwistors to D=6.
Particle 1stquantization
Firstquantization has been the most useful calculational tool in string theory;
similar advantages have not yet been realized for particles.
Dai & I analyzed 1stquantization for scalar theories.
Dai, Y. Huang, & I generalized this to 4D YangMills.
Hatsuda, Y. Huang, & I studied 1stquantization of 4D N=4 YangMills.
AdS/CFT
With Nastase, Roiban, and Hatsuda I studied a new version of the correspondence between 4D conformal
field theory and string theory on antide Sitter backgrounds, initiated by
Maldacena. Based on the
random lattice worldsheet, Dirac's projective lightcone, supertwistors,
and a double holography for both anti deSitter space and the 5sphere,
we found a relation in projective superspace to the conformal
field theory describing the constituents of strings (partons/preons), as
distinguished from the usual one describing open string states themselves (e.g.,
"gluons" instead of massless "rho mesons" in hadronic string language).
Dai, R.N. Huang, & I found the explicit propagator for the supergravity field strengths on the AdS₅×S⁵ background.
More strings
I showed how socalled Tduality,
rather than being a symmetry of certain string solutions, can actually be
considered a spontaneously broken symmetry of the full (super)string
theory.
I showed that the apparent phenomenon of closed strings appearing as bound
states of open strings actually occurs as a kinematic effect in the free theory,
analogously to a
similar phenomenon in field theory in two dimensions ("bosonization").
Feng and I showed how to use gauge covariant vertex operators in string theory that automatically give Smatrices with gauge independent external line factors.
Lee and I solved the longstanding problem of finding the BRST operator for the manifestly supersymmetric superstring, and used this formalism to give simpler calculations of tree & 1loop superstring amplitudes.
Strings on random lattices
I extended to superstrings the random matrix approach to string theory,
in which the string appears as a bound state of particles, and early results (with Feng)
suggest that the superstring arises as a bound state of a type of
supersymmetric quantum chromodynamics.
Biswas, Grisaru, and I calculated explicit ladder diagrams in random lattice theory to derive linear Regge trajectrories.
Extra dimensions
Biswas and I studied the various ways extra internal dimensions could be used to describe N=2 supersymmetric theories, and evaluate their actions. We also found a new type of dimensional reduction, radial instead of linear, which gives theories in (anti) de Sitter space from flat space.
Noncommutativity
Lee and I showed how to reproduce supergravity at one loop as a bound state
of super YangMills using higherderivative couplings, a result previously
thought unique to string theory. The mechanism is similar to the UV/IR
correspondence found in noncommutative field theory, but is Lorentz covariant.
Like string theory, this phenomenon uniquely requires D=10 and supersymmetry.
Hatsuda and I generalized to superspace results of Snyder on compact momentum space, which has the same form of Lorentz covariant noncommutativity, describing supersymmetric theories on a Lorentz covariant "lattice".
Short distance modifications to spacetime
I showed that the gravity implied by string theory weakens at short distances, as was suggested by its preonic substructure found in random lattice quantization, and implies the absence of black holes. Biswas, Mazumdar, & I generalized this to cosmology, showing the absence of a singularity at the Big Bang.
New 4D strings
I found new formulations of the twistor superstring (of Nair; Witten; Roiban, Spradlin, and Volovich; and Berkovits) that allowed its generalization offshell, and to a new string for which it is the tensionless limit.
Andreev and I proposed strings that perturbatively exhibit both asymptotic freedom and the usual Regge behavior and spectrum.
BEFORE STONY BROOK
Superspace
My early work ('77'83) involved mostly the use of superspace to treat
supersymmetric theories, including supergravity. Gates, Grisaru, Roček, and I
discovered methods for both deriving classical actions, and performing
Feynman graph calculations more simply than those in nonsupersymmetric
theories. I also found a new method of dimensional regularization
("dimensional reduction") which preserves supersymmetry, and is also
commonly used in QCD.
Strings
In later work ('83'88) I focused primarily on string theory. I invented
(covariant) string field theory. With Zwiebach I generalized these
methods outside of string theory to give a universal free field theory
action for arbitrary representations of the Poincaré group in arbitrary
dimensions. I also discovered new gauge symmetries of classical mechanics,
useful for strings.
THE FREE LIBRARY
Fields
I spent a considerable portion of 199699 writing the book "Fields"  the first
free comprehensive (731 pages) textbook on quantum (and classical) field
theory.
I recently released the third edition (885 pages).
It is published only electronically.
This book is available at the usual Web
archives (at arXiv.org
or my Web page,
which has more details).
Its approach to field theory is pragmatic, rather than traditional or
artistic: It includes practical techniques, such as the 1/N expansion
(color ordering) and spacecone (spinor helicity), and diverse topics, such
as supersymmetry and general relativity, as well as introductions to
supergravity and strings.
Other books
In 2001 I also released my 1988 book,
"Introduction to String Field Theory," freely to the Web
(e.g., at
arXiv.org) and, with the help of my coauthors
S.J. Gates, M.T. Grisaru, and M. Roček, our 1983 standard,
"Superspace, or One Thousand and One Lessons in Supersymmetry"
(at arXiv.org).
The program
Today most physics books (as well as almost all papers) are typeset in TeX.
This makes it possible for any author to release his book for free, with
no publishing costs to himself or the reader, should he so choose, either after
a period of commercial sales (and return of copyright by the publisher)
or immediately.
Such electronic distribution of books is more
convenient, cheaper, faster, and more ecologically friendly than paper
books. In particular, the PDF versions of my books have Web links and
clickable outline (contents) windows.
My hope is that these books will help set new standards in both format and
content that will make physics more accessible and relevant to students.
PUBLICATIONS, incl. CONFERENCE TALKS:
Complete
publication list (178 last time I looked)
Preprints at arXiv.org
Past year
STUDENTS
RESEARCH STUDENTS at Stony Brook (linked to PUBLICATIONS):
Hatsuda, Machiko  S'90S'91 
Theory Division, KEK
Tsukuba, Ibaraki
3050801, JAPAN 
mhatsuda@post.kek.jp 
Eßler, Fabian  S'91S'93 
Rudolf Peierls Centre for Theoretical Physics
University of Oxford
1 Keble Road
Oxford, OX1 3NP, UK

fab@thphys.ox.ac.uk 
Gasparakis, Charidimos  F'91F'95 
electronics 
charidimosg@msn.com 
Martinez, Mario  F'92S'94  (didn't finish Ph.D.)  
Weiser, Harold  F'92F'99   
Peeters, Bastiaan  S'93S'95 
finance 
bpeeters@feweb.vu.nl 
Schalm, Koenraad  F'95S'99 
InstituutLorentz for Theoretical Physics
University of Leiden
Leiden 2333CA, Netherlands

kschalm@lorentz.leidenuniv.nl 
Biswas, Tirthabir  F'00S'03 
Department of Physics
Loyola University
6363 St. Charles Avenue, Campus Box 92
New Orleans, LA 70118

tirthabir@yahoo.com 
Feng, Haidong  F'03S'07 
finance 
iamhfeng@gmail.com 
Lee, Kiyoung  F'03S'07 
Owens Community College
P.O. Box 10,000
Toledo, Ohio 436991947 
yirok2@gmail.com 
MartinezTorteya, Carlos  F'04S'10 
(didn't finish Ph.D.) 

Huang, Yutin  F'05S'09 
Department of Physics and Astronomy
National Taiwan University
Taipei 10617, Taiwan, ROC

yutinyt@gmail.com 
Dai, Peng  F'06F'09 
finance 
hanspengdai@gmail.com 
IrizarryGelpí, Melvin Eloy  F'08S'13 
Princeton, NJ 
melvineloy@gmail.com 
Jain, Dharmesh  F'09S'14 
Department of Physics and Astronomy
National Taiwan University
Taipei 10617, Taiwan, ROC

jkmsmkj@gmail.com 
Ju, ChiaYi  F'12 
Stony Brook 
chiayiju@gmail.com 
Poláček, Martin  F'13 
Stony Brook 
matho.polacek@gmail.com 
I also advised
Aleksandar
Miković and others at Maryland, and was the unofficial adviser of
Jon
Yamron and
Nathan
Berkovits at Berkeley.
COURSES TAUGHT @ Stony Brook (incl. lecture notes):
Relativity  PHY 408  S 95, 04 
Relativity  PHY 620  S 92, 93, 96, 99, F 03, 05, 07 
Quantum Field Theory  PHY 6101  F 97S 98, F 01S 02, F 04S 05, F 06S 07, F 08S 09, F 10S 11, F 12S 13 
Advanced Quantum Field Theory  PHY 621  S 08, 10 
String Theory (with others)  PHY 6223  SF 03, F 04∞ (& beyond) 
TIME SPENT TEACHING & ADVISING GRADUATE STUDENTS: 25%
HISTORY
DEGREES:
Univ. of California, Berkeley  6/7012/72  A.B.  Physics, Math. 
Univ. of California, Berkeley  1/73 6/77  Ph.D.  Physics 
GRADUATE ADVISOR: Martin B. Halpern
POSITIONS HELD:
Harvard University  7/777/79  Honorary Postdoctoral Fellow 
Brandeis University  3/796/79  Postdoctoral Fellow 
Inst. for Advanced Study  8/798/80  Postdoctoral Fellow 
Calif. Inst. of Technology  8/808/82  Postdoctoral Fellow 
Univ. of Calif., Berkeley  8/828/85  Postdoctoral Fellow 
Univ. of Md., College Park  8/856/87  Assistant Professor 
"  7/879/88  Professor 
State Univ. of N.Y., Stony Brook  9/88  Professor 
MISCELLANY
PRESENT ADDRESS:
C.N. Yang Institute for Theoretical Physics
State University of New York
Stony Brook, NY 117943840
Grant: NSF # PHY1316617 (P.I.: G. Sterman)
Awards, consulting, professional affiliations: none
Local expert on some computer stuff: Mac, TeX, WWW, etc.