A Group Blog on Physics

**Urs Schreiber:**Postdoctoral Position at the interface of Algebra, Conformal Field Theory and String Theory (December 5, 2006)- Postdoc position in algebra, CFT and strings.
**Robert H.:**More polymer oscillators (October 31, 2006)- The same day as the “Lessons from the LQG string” appeared on hep-th, there was another paper by Corichi,…
**Robert H.:**Lessons from the LQG string (October 17, 2006)- It’s now two years, that Giuseppe and I have put out out our paper comparing the usual quantisation of the…
**Aaron:**The Master constraint program in LQG (September 2, 2006)- I’m a little reluctant to post much on the master constraint program because I haven’t read much on it. But…
**Aaron:**The Harmonic Oscillator in LQG (September 2, 2006)- I’ve been trying to understand Thomas Thiemann’s riposte to the papers of Nicolai, Peeters and Zamaklar, Nicolai and Peeters and…
**Aaron:***Not Even Wrong*(August 19, 2006)- The physics blog-wars have hit the world of publishing with Peter Woit’s Not Even Wrong and Lee Smolin’s The Trouble…
**Urs Schreiber:**The n-Category Café (August 17, 2006)- New group blog: “The n-Category Cafe”.
**Urs Schreiber:**Synthetic Transitions (July 28, 2006)- On deriving 2-connection transition laws using synthetic differential geometry.
**Urs Schreiber:**Quillen’s Superconnections – Functorially (July 26, 2006)- On how to interpret the superconnections appearing on brane/anti-brane configurations in terms of functorial transport.
**Urs Schreiber:**K-Theory for Dummies, II (July 26, 2006)- Some remarks on K-theory and D-branes.
**Urs Schreiber:**Brodzki, Mathai, Rosenberg & Szabo on D-Branes, RR-Fields and Duality (July 20, 2006)- Mathai et al give a detailed analysis of the nature of D-branes, RR-charges and T-duality using and extending the topological/algebraic machinery known from “topological T-duality”.
**Urs Schreiber:**2-Palatini (July 19, 2006)- Some remarks on formulations of (super)gravity in terms of n-connections.
**Urs Schreiber:**Herbst, Hori & Page on Equivalence of LG and CY (July 18, 2006)- Hori and Herbst on equivalence of Landau-Ginzburg and Calabi-Yau TFT models using gauged linear sigma models.
**Urs Schreiber:**Gomi on Reps of p-Form Connection Quantum Algebras (July 14, 2006)- Gomi on the construction of projective unitary reps of centrally extended groups of p-form connections.
**Urs Schreiber:**Seminar on 2-Vector Bundles and Elliptic Cohomology, VI (July 13, 2006)- More detials on elliptic curves, formal groups and “classical” elliptic cohomology.
**Urs Schreiber:**Freed, Moore, Segal on p-Form Gauge Theory, II (July 11, 2006)- On Heisenberg groups appearing in the quantization of higher chiral gauge theories.
**Urs Schreiber:**Freed, Moore, Segal on p-Form Gauge Theory, I (July 10, 2006)- Some aspects of recent work by Freed, Moore and Segal on the quantum theory of abelian p-form fields and the grading of the Hilbert space by electric and magnetic flux modulo torsion.
**Urs Schreiber:**How many Circles are there in the World? (July 8, 2006)- On 2-torsors for suspended U(1).
**Urs Schreiber:**Gomi on Chern-Simons terms and central extensions of gerbe gauge groups (July 5, 2006)- Gomi on Chern-Simons field theories in higher dimensions and central extension of gerbe gauge groups.
**Urs Schreiber:**Seminar on 2-Vector Bundles and Elliptic Cohomology, V (June 28, 2006)- Part V of a seminar on elliptic cohomology and 2-vector bundles. Review of relations between elliptic cohomology and strings.
**Urs Schreiber:**Gukov on Surface Operators in Gauge Theory and Categorification (June 27, 2006)- Gukov relates knot theory to categorified quantum mechanics and the like.
**Urs Schreiber:**Kapranov and Getzler on Higher Stuff (June 22, 2006)- Lecture notes of talks by Kapranov on noncommutative Fourier transformation and by Getzler on Lie theory of L_oo algebras.
**Urs Schreiber:**Varieties and Schemes for Dummies, Part III (June 22, 2006)- Still more notes on elements of algebraic geometry.
**Urs Schreiber:**Varieties and Schemes for Dummies, Part II (June 22, 2006)- More notes on elements of algebraic geometry.
**Urs Schreiber:**Sharpe on Derived Categories and Strings on Stacks (June 21, 2006)- Slides of Eric Sharpe’s ESI talk on derived categories, strings on stacks and renormalization group flow.
**Urs Schreiber:**Varieties and Schemes for Dummies, Part I (June 20, 2006)- Notes on elements of algebraic geometry.
**Urs Schreiber:**Kapustin on SYM, Mirror Symmetry and Langlands, III (June 17, 2006)- The third part of the lecture.
**Urs Schreiber:**Kapustin on SYM, Mirror Symmetry and Langlands, II (June 17, 2006)- Second part of A. Kapustin’s talk.
**Urs Schreiber:**Soibelman on NCG of CFT and Mirror Symmetry (June 16, 2006)- Soibelman on collaps of CFTs on noncommutative target spaces.
**Urs Schreiber:**Kapustin on SYM, Mirror Symmetry and Langlands, I (June 15, 2006)- Kapustin lectures on mirror symmetry in twisted compactified SYM, realizing geometric Langlands.
**Urs Schreiber:**Roberts on Nonabelian Cohomology (June 15, 2006)- An old reference to a paper by Roberts on nonabelian cohomology.
**Urs Schreiber:**Kontsevich Lectures on Mirror Symmetry, I (June 14, 2006)- Kontsevich lectures on mirror symmetry I: TQFTs and CohFTs.
**Urs Schreiber:**Castellani on FDA in SuGra: gauge 3-group of M-Theory (June 12, 2006)- Castellani uses free differential algebra, and implictly Line n-algebra connections, for understanding the symmetries of 11D supergravity.
**Urs Schreiber:**Homological Mirror Symmetry Literature (June 10, 2006)- Some literature on homological mirror symmetry and related issues.
**Urs Schreiber:**Mathai on T-Duality IV: Distler on CFT Checks (June 10, 2006)- Jacques Distler comments on CFT checks of topological T-duality.
**Urs Schreiber:**Crane-Sheppeard on 2-Reps (June 9, 2006)- On linear 2-reps as discussed by Crane and Sheppeard.
**Urs Schreiber:**ESI Workshop on Homological Mirror Symmetry (June 4, 2006)- Kontsevich lectures at ESI on Homological Mirror Symmetry
**Urs Schreiber:**Going the Wrong Way - for Dummies (June 2, 2006)- The definition of the pullback of sheaves of modules.
**Urs Schreiber:**Mathai on T-Duality, III: Algebraic Formulation (June 2, 2006)- Mathai on elements of the C-star algebraic formulation of T-duality.
**Urs Schreiber:**Mathai on T-Duality, II: T-dual K-classes by Fourier-Mukai (June 2, 2006)- First part of V. Mathai’s talk on topological T-duality: T-dual K-classes by means of Fourier-Mukai transformation.
**Urs Schreiber:**Mathai on T-Duality, I: Overview (June 2, 2006)- Some elements of T-duality in the context of noncommutative topology. Part I: some context.
**Urs Schreiber:**Fourier-Mukai, T-Duality and other linear 2-Maps (June 1, 2006)- Examples for linear 2-maps.
**Urs Schreiber:**2-Spectral Theory, Part II (May 30, 2006)- Complete 2-bases of 2-eigenvectors (with an eye on Hecke eigensheaves and duality defects).
**Urs Schreiber:**Some Links (May 29, 2006)- A paper on TQFT and String Topology, some lecture notes on derived categories and a paper on TCFT.
**Urs Schreiber:**2-Spectral Theory, Part I (May 29, 2006)- Does a categorified spectral theorem connect duality defects in CFT with diagonizable Hecke-like 2-operators?
**Urs Schreiber:**2-Metric Geometry (May 25, 2006)- Categorifying Lawvere’s conception of metric spaces.
**Urs Schreiber:**Bunke on H, Part III (May 23, 2006)- Second part of U. Bunke’s talk on how to realize twisted deRham cohomology in terms of cohomology on gerbes.
**Urs Schreiber:**Bunke on H, Part II (May 23, 2006)- Transcript of talk by U. Bunke on twisted cohomology and cohomology on gerbes.
**Urs Schreiber:**Bunke on H, Part I (May 23, 2006)- U. Bunke et. al propose a (more) natural home for the twisted deRham cohomology appearing in Kalb-Ramond flux backgrounds.
**Urs Schreiber:**The FRS Theorem on RCFT (May 19, 2006)- Statement of the FRS theorem in rational conformal field theory.
**Urs Schreiber:**Hecke Eigensheaves and higher Eigenvectors (May 15, 2006)- More details on how Hecke eigensheaves are related to categorified eigenvectors.
**Urs Schreiber:**Pantev on Langlands, II (May 10, 2006)- Pantev lectures on Langlands duality, D-branes and quantization, part II.
**Urs Schreiber:**Pantev on Langlands, I (May 9, 2006)- Pantev lectures on Langlands duality, D-branes and quantization.
**Urs Schreiber:**Eigenbranes and CatLinAlg (May 7, 2006)- The concept of eigenbranes, which appears in the context of geometric Langlands, and the categorified linear algebra of FRS.
**Urs Schreiber:**Formal HQFT (May 4, 2006)- Porter and Turaev on formal HQFT.
**Urs Schreiber:**Talk in Bonn on String 2-Group (April 26, 2006)- Talk on the String 2-Group in Bonn.
**Urs Schreiber:**Huybrechts on Branes in K3, II (April 21, 2006)- Huybrechts analyzes the relation between topological and BPS branes on K3 surfaces, part II.
**Urs Schreiber:**Huybrechts on Branes in K3, I (April 21, 2006)- Huybrechts analyzes the relation between topological and BPS branes on K3 surfaces.
**Urs Schreiber:**Jurco on Gerbes and Stringy Applications (April 19, 2006)- Jurco reviews some facts concerning nonabelian gerbes in string theory.
**Urs Schreiber:**A Note on RCFT and Quiver Reps (April 18, 2006)- A note on how the structure of RCFT is encoded in something very similar to a quiver representation.
**Urs Schreiber:**(R)CFT on more general 2-Categories (April 18, 2006)- RCFTs can apparently be defined as 2-functors on 2-paths in Riemann surfaces. Can this be generalized to other domain 2-categories?
**Urs Schreiber:**More Vietri Talks (April 16, 2006)- Talks on topological membranes and twisted K-theory
**Urs Schreiber:**RR-Forms and Algebroids (April 12, 2006)- RR forms and free graded differential algebras.
**Urs Schreiber:**Generalized Worldsheets? (April 12, 2006)- What is known about generalizations of world sheets away from the concept of manifolds?
**Urs Schreiber:**Picard and Brauer 2-Groups (April 5, 2006)- On the Picard 2-group and the Brauer 2-group of a monoidal category.
**Urs Schreiber:**More by Bartels on 2-Bundles (April 4, 2006)- Refined notes by Toby Bartels on 2-bundles.
**Urs Schreiber:**Particles, Strings and the Early Universe in Hamburg (April 4, 2006)- A planned collaborative research center in Hamburg, on strings, HEP and cosmology.
**Urs Schreiber:**Categorified Gauge Theory in Chicago (April 4, 2006)- Conference with emphasis on categorified gauge theory, covering gerbes and the String group.
**Urs Schreiber:**String Localization, Once Again (March 29, 2006)- Recap of string localization.
**Urs Schreiber:**Exotic String Statistics (March 28, 2006)- On generalizations of braid group statistics from points to strings.
**Urs Schreiber:**Gerbes and Quantization (March 28, 2006)- Report on a paper on gerbes and quantization.
**Urs Schreiber:**Cats in MathPhys (March 26, 2006)- List of applications of category theory in mathematical physics and string theory.
**Urs Schreiber:**Stevenson, Henriques on String(n) (March 22, 2006)- Stevenson and Henriques have articles on the String group.
**Urs Schreiber:**Remarks on 2-Reps (March 16, 2006)- More on 2-representations of the String(n) group.
**Urs Schreiber:**Vertex Algebras et al. - Some Literature (March 14, 2006)- Literature on vertex algebras and related topics.
**Urs Schreiber:**Gerbes and Quantum Field Theory (March 14, 2006)- Mickelsson on the role of gerbes in the study of anomalies in quantum field theory.
**Urs Schreiber:**Remarks on String(n) (March 11, 2006)- Is Stolz/Teichner’s String-connection a 2-connection in an associated 2-bundle?
**Urs Schreiber:**What IS a superfield, really? (March 7, 2006)- On the true (functorial) nature of superfields.
**Urs Schreiber:**Hilbert Uniformization of Moduli Space (March 7, 2006)- On a result by Boedigheimer on Hilbert uniformization.
**Urs Schreiber:**nEFT at Schloss Mickeln, Part II (March 6, 2006)- Talk by Johannes Ebert on CFT partition functions and modular forms.
**Urs Schreiber:**nEFT at Schloss Mickeln, Part I (March 4, 2006)- Talk by E. Markert on concepts and results in describing generalized cohomology in terms of euclidean field theory. Part I. Mostly pesonal remarks on the general program.
**Urs Schreiber:**Superpoints (March 2, 2006)- First notes from a workshop on elliptic objects.
**Urs Schreiber:**Kapranov and Ganter on 2-Characters (February 27, 2006)- Ganter and Kapranov have a paper on traces and characters of 2-categorical representations of groups.
**Urs Schreiber:**Graphs, Operads and Renormalization (February 23, 2006)- On a category of graphs appearing in Riemann surface moduli spaces and in renormalization theory.
**Urs Schreiber:**On Transport Theory (February 17, 2006)- Overview of the theory of n-transport.
**Urs Schreiber:**1st Northern German String workshop (February 12, 2006)- A string workshop at the ZMP.
**Urs Schreiber:**Problemi Attuali di Fisica Teorica 06 (February 9, 2006)- This year’s meeting in Vietri.
**Urs Schreiber:**Workshop on Gerbes, Groupoids and QFT (February 9, 2006)- Announcement of a workshop on gerbes and QFT.
**Urs Schreiber:**FRS Reviews (February 8, 2006)- Two new reviews on FRS formalism.
**Urs Schreiber:**Special Ambidextrous Adjunctions (February 8, 2006)- Question on special ambidextrous adjunctions.
**Urs Schreiber:**Philosophy of Real Mathematics (February 7, 2006)- David Corfield on Jacob Lurie’s survey of elliptic cohomology.
**Urs Schreiber:**Lauda & Pfeiffer on Open-Closed Topological Strings, II (February 6, 2006)- Lauda and Pfeiffer on open/closed topological strings from state sums.
**Urs Schreiber:**Seminar on 2-Vector Bundles and Elliptic Cohomology, IV (February 5, 2006)- First session, third part.
**Urs Schreiber:**Seminar on 2-Vector Bundles and Elliptic Cohomology, III (February 5, 2006)- First session, second part.
**Urs Schreiber:**Seminar on 2-Vector Bundles and Elliptic Cohomology, II (February 3, 2006)- First session, first part.
**Urs Schreiber:**Seminar on 2-Vector Bundles and Elliptic Cohomology, I (February 2, 2006)- Review of the 2-vector approach towards elliptic cohomology. Part I.
**Urs Schreiber:**Exploring the Blogosphere (February 2, 2006)- Articles on math/physics weblogs.
**Urs Schreiber:**Orbifold String Topology: Paths in Smooth Categories (February 2, 2006)- A 2-functorial conception of Lupercio & Uribe’s loop groupoid.
**Urs Schreiber:**Moerdijk on Orbifolds, III (February 1, 2006)- Transcript of second of two lectures by I. Moerdijk on orbifolds.
**Urs Schreiber:**Moerdijk on Orbifolds, II (January 31, 2006)- Transcript of first of two lectures by I. Moerdijk on orbifolds.
**Urs Schreiber:**Moerdijk on Orbifolds, I (January 31, 2006)- I. Moerdijk lectures on the theory of orbifolds.
**Urs Schreiber:**Spans, 2-Hilbert Spaces and Module Categories (January 27, 2006)- How to obtain 2-Hilbert spaces from span categories.
**Urs Schreiber:**(String) Physics from (Higher) Algebra, II (January 24, 2006)- Some revisions on the program of categorifying quantum mechanics and relating it to string physics.
**Urs Schreiber:**TCFT, Part I (January 10, 2006)- Some basic ideas of TCFT.
**Urs Schreiber:**(String) Physics from (Higher) Algebra (January 9, 2006)- One further refinement of the tale called ‘Strings from categorified quantum mechanics.’
**Urs Schreiber:**Nekrasov Lecture Online II (January 5, 2006)- The third session of Nikita Nekrasov’s lecture in Jerusalem. Some news on the Cech description of the pure spinor string.
**Urs Schreiber:**Nekrasov Lecture Online I (January 4, 2006)- Quicktime video of Nikita Nekrasov’s lectures on the pure spinor superstring is available online.
**Urs Schreiber:**Confusion and Connes Fusions (January 4, 2006)- Elements of Connes fusion.
**Urs Schreiber:**Bimodules, Adjunctions and the Internal Hom, Part II (January 3, 2006)- More on bimodules, adjunctions, module categories and internal homs.
**Urs Schreiber:**Bimodules, Adjunctions and the Internal Hom, Part I (January 2, 2006)- Notes on certain phenomena concerning algebra objects and adjunctions in tensor categories.
**Urs Schreiber:**More by Gustavsson on Non-Abelian Strings (January 2, 2006)- More by A. Gustavsson on nonabelian strings
**Urs Schreiber:**Winter School on Elliptic Objects (December 24, 2005)- Winter School on Elliptic Objects
**Urs Schreiber:**Müger on Doplicher-Roberts (December 23, 2005)- Mueger has a new proof of Doplicher Roberts.
**Urs Schreiber:**Equivariant Structures on Gerbes (December 23, 2005)- Some literature on gerbes on orbifolds.
**Urs Schreiber:**Unoriented Strings and Gerbe Holonomy (December 22, 2005)- New preprint on gerbe holonomy over unoriented surfaces.
**Urs Schreiber:**3D TFT Literature (December 20, 2005)- Literature on 3D TFT and its relation to 2D CFT.
**Urs Schreiber:**Lauda on Frobenius Algebras and Open Topological Strings (December 15, 2005)- Lauda on Frobenius algebras and open topological strings and membranes.
**Urs Schreiber:**Frobenius Algebras and 2D QFT (December 15, 2005)- On Frobenius algebras in 2D TFT and CFT.
**Urs Schreiber:**Topological Strings from 2-Transport (December 14, 2005)- Fukuma-Hosono-Kawai TFT is obtained from 2-transport in Vect.
**Urs Schreiber:**E. Sharpe on Derived Categories (December 13, 2005)- Encyclopedia article on derived categories by E. Sharpe.
**Urs Schreiber:**D-Branes in Landau-Ginzburg Models (December 8, 2005)- Some elementary background on B-branes in LG models.
**Urs Schreiber:**NABGs from 2-Transport I: Synthetic Bibundles (December 7, 2005)- Deriving nonabelian bundle gerbes from 2-functor 1-morphisms.
**Urs Schreiber:**2-Connections on 2-Bundles (December 2, 2005)- 2-connections on 2-bundles once again
**Urs Schreiber:**“Area Metric” Manifolds (November 29, 2005)- On Schuller and Wohlfarth on area metric geometry and strings.
**Urs Schreiber:**Line-2-Bundles and Bundle Gerbes (November 22, 2005)- On parallel transport of string in line-2-bundles.
**Robert H.:**KK Reference (November 17, 2005)- I am looking for a reference for the fact that it is impossible to get non-abelian gauge groups or chiral…
**Urs Schreiber:**CFT and SLE (November 15, 2005)- Notes on the SLE approach to CFT.
**Urs Schreiber:**Lauda & Pfeiffer on Open-Closed Topological Strings (November 13, 2005)- Lauda and Pfeiffer fill some gaps in the rigorous understanding of open topological strings.
**Urs Schreiber:**Strings on Stacks II (November 9, 2005)- More on Eric Sharpe and Tony Pantev on strings on stacks.
**Urs Schreiber:**Strings on Stacks I (November 8, 2005)- Notes on E. Sharpe’s work on strings on stacks.
**Urs Schreiber:**2-Equivariance and “Weak Pullback” (November 7, 2005)- On equivariant 2-bundles and strings on orbifolds.
**Urs Schreiber:**Classical, Canonical, Stringy (November 2, 2005)- A stringy 3-form generalization of 2-form symplectic canonical mechanics.
**Urs Schreiber:**Gerbes, strings, and Nambu brackets (November 1, 2005)- How are symplectic forms and Poisson brackets related to closed 3-forms and string physics?
**Urs Schreiber:**Sheaves of CDOs (October 31, 2005)- Literature on Cech-methods in CFT.
**Urs Schreiber:**Plasma-Ball Duals of Black Holes (October 27, 2005)- Aharony on plasma-ball duals to black holes and Berkooz on Q-ball excitations in MSSM as inflaton candidates.
**Urs Schreiber:**ZMP Colloquium, Thursday: Nekrasov on Pure Spinor Superstring (October 20, 2005)- A talk by N. Nekrasov on the pure-spinor superstring and its apparent relation to gerbes.
**Urs Schreiber:**Kalkkinen: Nonabelian Gerbes from twisted SYM (October 18, 2005)- Kalkkinen has a new paper where he points out relations between twisted SYM on 5-branes and nonabelian gerbes.
**Urs Schreiber:**Synthetic Differential Geometry and Surface Holonomy (October 11, 2005)- Synthetic differential geometry and its use in the literature on higher gauge theory.
**Urs Schreiber:**What is “the” Gerbe of a 2-Bundle? (October 5, 2005)- An observation on how a gerbe arises from a 2-bundle in an intrinsic (rather than cocyclic) way.
**Urs Schreiber:**Literature on Exotic R4s (September 27, 2005)- Question on literature on exotic R4s.
**Urs Schreiber:**Center for MathPhys Opening Colloquium in Hamburg (September 23, 2005)- Colloquium on mathematical aspects of string and field theory in Hamburg.
**Urs Schreiber:**A. Gustavsson on Surface Holonomy (September 23, 2005)- A new proposal for nonabelian surface holonomy by Andreas Gustavsson.
**Robert H.:**What does the density of vacua predict? (September 21, 2005)- Imagine a room where the floor has the profile (1)z(x,y)=sin(π/x). z(x,y) = \sin(\pi/x). Now, you throw a ball into…
**Urs Schreiber:**Gerbes, Algebroids and Groupoid Bundles, the emerging Picture (September 2, 2005)- The big picture of gerbes, algebroids, groupoid bundles and some generalized geometry.
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, VII (August 24, 2005)- You’ll have noticed that I failed to report on the talks of the last two days in Oberwolfach, either…
**Urs Schreiber:**Lecture Notes on Higher Gauge Theory (August 22, 2005)- John Baez’s lecture notes on Higher Gauge Theory, Homotopy Theory and n-Categories,
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, VI (August 20, 2005)- Jurco’s talk on classification of gerbes.
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, V (August 17, 2005)- Wednesday in Oberwolfach.
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, IV (August 16, 2005)- Tuesday in Oberwolfach: stacks, gerbes, M-theory and K-theory.
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, III (August 15, 2005)- Talks on gerbes in WZW models and some other stuff.
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, II (August 15, 2005)- Monday morning at Oberwolfach: M-theory for mathematicians and 2-gerbes for supergravity.
**Urs Schreiber:**K-theory for dummies, I (August 12, 2005)- A list of some basic concepts in K-theory.
**Urs Schreiber:**CFT, Gerbes and K-Theory in Oberwolfach, I (August 12, 2005)- On a workshop in Oberwolfach next week and some details on joint ideas with Igor Bakovic.
**Robert H.:**Background independence (August 2, 2005)- Last week, Lee Smolin has put a paper on the arxive which on nearly fifty pages does not contain any…
**Guest:**Non-Commutative Geometry School I (July 27, 2005)- I never meant to say much about this week, but in a completely unexpected turn of events yesterday, Getzler…
**Guest:**Streetfest Workshop 3 (July 24, 2005)- Let’s start with Katzarkov’s talk on ‘Mirror symmetry and manifolds of general type’. He began with a question: are…
**Urs Schreiber:**Q: Open Strings in KR Background (July 23, 2005)- How to understand the coupling of the KR field to open strings.
**Guest:**Streetfest Workshop II (July 22, 2005)- The Streetfest ended yesterday with a talk by Eugenia Cheng on degenerate higher categories and the periodic table of…
**Guest:**Streetfest Workshop I (July 18, 2005)- Greetings from Canberra! It is very pleasant here. There was a good frost this morning and some black swans…
**Urs Schreiber:**Costello on Open Topological Strings (July 17, 2005)- On a paper about open topological strings by K. Costello.
**Urs Schreiber:**Talks in Hamburg, Lectures in Bad Honnef (July 15, 2005)- Random notes on HQFT and BCFT.
**Guest:**Thursday at the Streetfest III (July 14, 2005)- Gorbunov decided to talk about Gerbes of Chiral Differential Operators instead of what was in his abstract, motivation being…
**Guest:**Thursday at the Streetfest II (July 14, 2005)- David here I thought I’d talk a bit about Ezra Getzler’s talk (which was only loosely connected to his…
**Guest:**Thursday at the Streetfest I (July 13, 2005)- Well it’s Thursday morning and I thought I’d say hi now because it’s going to be a very busy…
**Guest:**Wednesday at the Streetfest IV (July 13, 2005)- Well, I’m going to have dinner with Marnie and David and some other people, but I have a little…
**Guest:**Wednesday at the Streetfest IV (July 13, 2005)- Well, I’m going to have dinner with Marnie and David and some other people, but I have a little…
**Guest:**Wednesday at the Streetfest III (July 13, 2005)- Besides Bouwknegt’s talk on D-branes and generalized geometry, which Marnie and David are writing about, and Mueger’s talk on…
**Guest:**Wednesday at the Streetfest II (July 13, 2005)- Hi - I’ve decided to join in the fun and write a little about Michael Mueger’s talk in the…
**Guest:**Wednesday at the Streetfest I (July 13, 2005)- Bouwknegt started Wednesday with an apology for not being a category theorist. The main focus of the talk (I…
**Guest:**Tuesday at the Streetfest III (July 13, 2005)- Where were we. Yes - Bondal on derived categories of toric varieties… Idea 1: for an algebraic variety XX…
**Guest:**Tuesday at the Streetfest II (July 12, 2005)- Yesterday was a bit of a blur for me - lack of sleep in the previous week catching up,…
**Guest:**Tuesday at the Streetfest I (July 12, 2005)- Hello again! Wednesday already here. I already have 50 pages of notes. It’s quite overwhelming. Now let’s see. Kapranov…
**Guest:**Monday at the Streetfest II (July 12, 2005)- David here - I thought I’d mention some of the stuff that went on in the afternoon - a…
**Guest:**Monday at the Streetfest I (July 11, 2005)- While others report from conferences on Strings or Loops, in Sydney we are enjoying the balmy winter and the…
**Urs Schreiber:**2-Holonomy in Terms of 2-Torsors (July 5, 2005)- Details on 2-holonomy in terms of 2-torsors and some pointers to the Streetfest conference.
**Urs Schreiber:**From Loop Space Mechanics to Nonabelian Strings (June 23, 2005)- My thesis.
**Robert H.:**Talking to myself (May 26, 2005)- Since nobody answered my question about how to properly generalize the calibration condition for BPS-branes if the gauge field…
**Urs Schreiber:**String(n), Part II (May 18, 2005)- Review of issues related to String(n).
**Urs Schreiber:**String(n), Part I (May 18, 2005)- Review of issues related to String(n).
**Urs Schreiber:**Nonabelian Weak Deligne Hypercohomology (May 17, 2005)- Generalizing Deligne cohomology to the nonabelian and weak case.
**Urs Schreiber:**PSM and Algebroids, Part V (May 16, 2005)- Transitions in a p-bundle in terms of algebroid morphisms.
**Urs Schreiber:**PSM and Algebroids, Part IV (May 13, 2005)- Last time I discussed how Lie pp-algebroids (and hence Lie pp-algebras) and dg-algebras on graded vector spaces of maximal…
**Urs Schreiber:**PSM and Algebroids, Part III (May 4, 2005)- On the equivalence between algebroids, dg algebras and Lie p-algebras, the definition of algebroid YM theories and the relation to generalized geometry and abelian p-bundles and p-gerbes.
**Urs Schreiber:**PSM and Algebroids, Part II (April 29, 2005)- How Courant algebroids gives rise to L_infinity algebras.
**Robert H.:**Calibrations with gauge field (April 21, 2005)- Assume some closed string background preserving some susy. This comes with at least one Killing spinor whose square can…
**Urs Schreiber:**Akhmedov comments (April 20, 2005)- More on Akhmedov’s ideas concerning 2D TFTs.
**Urs Schreiber:**Weak NABG (April 15, 2005)- On weak nonabelian bundle gerbes.
**Urs Schreiber:**PSM and Algebroids, Part I (April 14, 2005)- There seem to be interesting relations of the Poisson σ\sigma-model (PSM) and of Lie algebroids to all kinds of…
**Urs Schreiber:**Open topological strings (April 13, 2005)- Some literature on open topological strings.
**Robert M.:**The arXiv in your pocket. (April 13, 2005)- As pointed out on several other blogs, Joanna Karczmarek has been testing the waters with a downloadable version of the…
**Aaron:**Susskind on wormholes (April 11, 2005)- Lenny Susskind was recently here and discussed his recent paper on wormholes. As you probably know, he’s mentioned some…
**Urs Schreiber:**Lessons from low Dimensions (April 9, 2005)- I am currently visting a CFT workshop at University of Bonn, Lessons from low Dimensions - the many Aspects of Conformal Field Theory.
**Urs Schreiber:**New preprint: From Loop Groups to 2-Groups (and the String Group) (April 7, 2005)- We have a new preprint demonstrating a relation between weak Lie 2-algebras, 2-groups coming from centrally extended loop groups and the group String(n).
**Urs Schreiber:**2-NCG: First Refinement (April 1, 2005)- Is 2-NCG an April Fool’s joke?
**Urs Schreiber:**Akhmedov: Nonabelian 2-Holonomy using TFT (March 31, 2005)- Discussion of Akhmedov’s paper on 2-holonomy.
**Urs Schreiber:**Derived Categories for Dummies, Part IV (March 22, 2005)- How branes and strings are described by the derived category of coherent sheaves.
**Urs Schreiber:**Derived Categories for Dummies, Part III (March 20, 2005)- Elementary aspects of derived categories of quiver representations – plus a remark on how this relates to 2-bundles.
**Urs Schreiber:**Derived Categories for Dummies, Part II (March 19, 2005)- Review of the definition of derived functors.
**Urs Schreiber:**Rasetti: Quantum Computers based on TQFT (March 19, 2005)- Rasetti proposes that topological quantum field theories may be models for P=NP-quantumcomputers.
**Urs Schreiber:**Talk at IIASS: Nonabelian Strings (March 16, 2005)- Slides for my talk at the IIASS on nonabelian strings.
**Urs Schreiber:**Derived categories for dummies, Part I (March 13, 2005)- Some facts about derived categories. And an open question…
**Urs Schreiber:**Quiver reps and vector 2-bundles (March 11, 2005)- A note on how quiver reps seem to be related to vector 2-bundles as in Baas,Dundas&Rognes.
**Urs Schreiber:**What’s next (February 24, 2005)- I have just returned from my two week visit of John Baez’s group at UC Riverside, which was extremely nice…
**Urs Schreiber:**Project: 2-NCG (February 15, 2005)- A discussion of categorified NCG and its relation to superstrings.
**Urs Schreiber:**Conversation with Kea: Categorified NCG (February 11, 2005)- Conversation with Kea on NCG and categorification.
**Robert H.:**To baldly go where no man went before (February 10, 2005)- In his reference frame, Lubos reports on a seminar by Reall on higher dimensional black holes and black rings and…
**Urs Schreiber:**Categorified Gauge Theory and M-Theory (February 9, 2005)- Does categorification of gauge theory know about the dimensions of the fundamental objects in M-theory?
**Urs Schreiber:**2-Holonomy LEGO (February 3, 2005)- Category LEGO used to define and discuss global nonabelian 2-holonomy.
**Urs Schreiber:**New paper: 2-Connections on 2-Bundles (December 30, 2004)- Mine and John Baez’s paper ‘2-connections on 2-bundles’ is available as a preprint.
**Urs Schreiber:**Re: Categorified Gauge Theory (December 27, 2004)- Comments on how nonabelian surface holonomy relates to nonabelian volume integrals.
**Urs Schreiber:**Nonabelian Self-Duality (December 15, 2004)- This is a followup to Peter Woit’s recent blog entry Langlands Program and Physics. There, Peter mentions the following…
**Urs Schreiber:**Re: Category Theory and Physics (December 3, 2004)- Reply to Lubos’s comments on the last entry on categories and strings.
**Urs Schreiber:**Categorified Points: Strings as Morphisms (November 24, 2004)- Over at sci.math.research there are some comments on categorification and its relation to string theory. Of course categories, being…
**Urs Schreiber:**Weak groups, hard computation (November 18, 2004)- Results on 2-bundles with coherent structure 2-groups.
**Urs Schreiber:**Nonabelian gerbes with connection and curving from 2-bundles with 2-holonomy (November 3, 2004)- A proof that a 2-bundle with 2-holonomy defines a nonabelian gerbe with certain connection and curving.
**Robert H.:**Effective theories and gravity (October 29, 2004)- To rebut fears that having my own blog would let me forget about the coffee table i would like…
**Urs Schreiber:**Thoughts on n-cube Scaling on 5-Branes (October 27, 2004)- Some thoughts on possible formal reasons for the n-cube scaling of degrees of freedom on 5-branes.
**Urs Schreiber:**Re: Self-dual strings and M5-brane anomalies (October 22, 2004)- Comment on Lubos’ comment on Berman&Harvey’s Self-Dual String Anomalies.
**Urs Schreiber:**2-bundles (October 19, 2004)- Finally there is a paper on 2-bundles.
**Urs Schreiber:**Tensionless strings and Polyakov’s loops (October 14, 2004)- Aspects of tensionless strings.
**Robert M.:**Bryce DeWitt (October 3, 2004)- In my last post I didn’t give very many details about the talks at the Quantum Theory of Black…
**Robert M.:**Finally! (September 19, 2004)- Okay, I’m a bit embarassed but I’ve finally gotten around to contributing something to the String Coffee Table. I’m embarassed…
**Urs Schreiber:**DDF=Pohlmeyer known in 1981 (September 16, 2004)- Readers of this blog will recall that I was involved in some thinking about Pohlmeyer invariants. It all started with…
**Urs Schreiber:**States of string in non-abelian 2-form background (September 12, 2004)- Strings in non-abelian 2-form backgrounds again: Some conceptual issues.
**Urs Schreiber:**r-flatness = 2-associativity (August 30, 2004)- I am further discussing loop space-, surface- and and 2-group-holonomy with those interested. While trying to convince the 2-group-theorists…
**Urs Schreiber:**News release on emergent string spacetime (August 27, 2004)- My friend Rüdiger Vaas, who is working as a science journalist for the german science magazin Bild der Wissenschaft,…
**Urs Schreiber:**On loop space and 2-group holonomy (August 27, 2004)- A pdf with my notes on the relation between loop space holonomy and 2-group holonomy is now available.
**Urs Schreiber:**Why does 2-group theory miss surface holonomies with nonvanishing B+F? (August 24, 2004)- One more observation about the relation between 2-group theory and loop space holonomy.
**Urs Schreiber:**1+1D LQG is really about boundary states (August 23, 2004)- What does LQG have to do with boundary states?
**Urs Schreiber:**Super-Pohlmeyer invariants and boundary states for non-abelian gauge fields (August 20, 2004)- I have just submitted the following to the preprint server: Urs Schreiber: Super-Pohlmeyer invariants and boundary states for non-abelian…
**Urs Schreiber:**Everybody agrees on the non-abelian boundary state! (August 19, 2004)- I realize that the different definitions of the non-abelian boundary state in the literature all agree.
**Urs Schreiber:**Microscopic relation between loop space connections and 2-group holonomies (August 18, 2004)- I discuss how loop space holonomies and 2-group holonomies are related.
**Urs Schreiber:**Escape from the Fog (August 16, 2004)- Report from vacation in Norway - and the inevitable remarks on some string theory.
**Urs Schreiber:**On Holiday (July 30, 2004)- I’ll be on holiday the next two weeks.
**Urs Schreiber:**A bird, a plane? No, super-Pohlmeyer! (July 27, 2004)- Recently I had talked about how I think Pohlmeyer invariants are related to boundary states of D-branes with gauge…
**Urs Schreiber:**More remarks on flat loop space connections (July 23, 2004)- More comments on flat connections on loop space and their relation to surface holonomies.
**Urs Schreiber:**Three ways to loop flatness (July 22, 2004)- Today I was contacted by Luiz Agostinho Ferreira who kindly called my attention to the paper Orlando Alvarez &…
**Urs Schreiber:**To loose or not to loose information (July 22, 2004)- Comment on Hawking’s talk on the black hole information loss problem.
**Urs Schreiber:**Talking to ’t Hooft about tossing TVs (July 19, 2004)- Summary of a talk by ’t Hooft.
**Urs Schreiber:**Mathematical loop space literature (July 15, 2004)- Readers of my writings will have noticed that I mention the tem loop space from time to time. Now, I…
**Urs Schreiber:**Nonabelian B-field equations of motion (July 13, 2004)- I try to derive the equations of motion of a nonabelian B-field from boundary state divergences.
**Urs Schreiber:**Not Abelian - but Flat (July 12, 2004)- The crucial condition for non-abelian 2-form connections is their flatness in loop space.
**Urs Schreiber:**Scandinavian but not Abelian (July 9, 2004)- I have attended a conference in Karlstad and thought about nonabelian 2-forms.
**Urs Schreiber:**From Paris to Karlstad (via Bonn) (July 4, 2004)- I am preparing for talks in Bonn and Karlstad.
**Urs Schreiber:**Cabinet de Curiosites dot com - STRINGS 04 (June 30, 2004)- The annual string theory conference is taking place at College de France in Paris this year. Fortunately this is…
**Urs Schreiber:**Nonabelian 2-form connection from SCFT deformation (June 21, 2004)- I show how the loop space connection of a nonabelian 2-form arises from the obvious SCFT deformation.
**Urs Schreiber:**Pohlmeyer invariants and states of the IIB matrix model (June 13, 2004)- Discussion of a relation between Pohlmeyer invariants and distributions of D(-1) branes which solve the IIB matrix model.
**Urs Schreiber:**Open string backgrounds from boundary state deformations (June 11, 2004)- Review of some aspects of the boundary state deformation technique studied by Koji Hashimoto.
**Urs Schreiber:**String entropy and black hole correspondence (June 10, 2004)- Brief summary of aspects of the string/black hole correspondence principle.
**Urs Schreiber:**Experiments probing quantum gravity (June 10, 2004)- List of experiments that try to probe quantum gravity in one way or another.
**Urs Schreiber:**Sigh. (June 7, 2004)- Bogdanov and Bogdanov have done it again.
**Robert H.:**Unlooping the LQG string (May 26, 2004)- A report on Thomas Thiemann’s seminar at DAMTP on his quantization of the bosonic string.
**Urs Schreiber:**CFTs from OSFT! (May 19, 2004)- The relation between classical SFT solutions and (boundary) conformal field theories is further discussed.
**Urs Schreiber:**Referee reports on SCFT deformations and Pohlmeyer invariants (May 13, 2004)- Readers of this weblog will recall that we had discussed here two drafts which I have meanwhile submitted to JHEP….
**Urs Schreiber:**Talk: N=2 NCG, fields and strings (May 3, 2004)- I am giving a talk at the Hamburg theory seminar on discrete NCG, fields and strings.
**Urs Schreiber:**CFTs from OSFT? (April 29, 2004)- A comment about a relation between string field theory and deformed CFTs on the worldsheet.
**Urs Schreiber:**Billiards at half-past E10 (April 26, 2004)- Aspects of sigma-models on Kac-Moody groups.
**Urs Schreiber:**New York, New York (April 23, 2004)- I have visited Ioannis Giannakis in New York, discussing superfconformal deformations.
**Urs Schreiber:**Power Supply (April 14, 2004)- I am visiting the AEI in Potsdam, discussing Pohlmeyer invariants and issues of quantization of string.
**Urs Schreiber:**Billiards, random matrices, M-theory and all that (April 8, 2004)- I am currently at a seminar on quantum chaos and related stuff. You cannot enjoy meetings like these without…
**Urs Schreiber:**Notions of string-localization (March 30, 2004)- Bert Schroer made me aware of the notion of ‘string-localized fields’, which are quite different from ordinary string fields.
**Urs Schreiber:**Visualization of Superstring States (March 18, 2004)- Heuristic visualization of the massless states of superstring.
**Urs Schreiber:**DPG Symposium 2004 (March 13, 2004)- I am on my way to the spring conference of the German Physical Society, the Frühjahrstagung der Deutschen Physikalischen Gesellschaft…
**Urs Schreiber:**Introductory String Theory Seminar (March 11, 2004)- List of introductory literature for string theory.
**Urs Schreiber:**Poll for sci.physics.strings (March 9, 2004)- Probably everybody has seen the Call for Votes for the creation of a new USENET newsgroup with the proposed…
**Urs Schreiber:**Simple but not trivial (March 8, 2004)- Discussion of a paper concerned with constant R-R 2-form background in NSR formalism.
**Urs Schreiber:**Before the flood (March 5, 2004)- On how to approach Type II strings by abstract differential calculus.
**Urs Schreiber:**[Admin.] How to participate in the String Coffee Table dicussion (February 21, 2004)- A list of tips and tricks for how to participate in the discussion at the String Coffee Table.
**Urs Schreiber:**The joy of IIB Matrix Models (February 20, 2004)- As readers of sci.physics.research might remember, a while ago I had learned about the IIB Matrix Model and had…
**Urs Schreiber:**Torsion Gravity from String Theory (February 15, 2004)- I was asked by A. Pelster, who has worked on torsion gravity together with H. Kleinert and F. Hehl,…
**Urs Schreiber:**[Review] DDF states (January 29, 2004)- The recent discussion about attempts to quantize the (super-)string by studying its algebra of classical invariants (i.e. of phase…
**Urs Schreiber:**Pohlmeyer charges, DDF states and string-gauge duality (January 29, 2004)- It’s half past two in the morning here in central Europe and a can’t sleep because my brain is thinking…
**Urs Schreiber:**Thiemann’s quantization of the Nambu-Goto action (January 27, 2004)- Aspects of the recent paper by Th. Thiemann on the ‘LQG-string’ are discussed.
**Urs Schreiber:**The search for discrete differential geometry (January 26, 2004)- At first it may look like a trivial problem whose solution should have been known for ages, being used…
**Urs Schreiber:**[Review] Type II on AdS_3, Part I: Lightcone spectrum (January 26, 2004)- The calculation of the exact lightcone spectrum of superstrings on AdS_3 x S^3 is reviewed as a preparation for a demonstration of perturbative calculations of the same thing using curvature corrections to the Penrose limit.
**Urs Schreiber:**[Exercise] Canonical analysis of D-string action (January 15, 2004)- The author tries to work his way through the canonical anaylsis of the D-string action. Help him! :-)
**Urs Schreiber:**Classical deformations of 2d SCFTs - Part II: Algebra Isomorphisms (December 30, 2003)- It has been shown in Part I (see also hep-th/0401175) that the modes of the KK-deformed exterior derivative d…
**Urs Schreiber:**Classical deformations of 2d SCFTs - Part I: Loop space (December 23, 2003)- Motivated by the representation of the classical super Virasoro constraints as generalized Dirac-Kaehler constraints (d±d +)|ψ⟩=0(\mathbf{d} \pm \mathbf{d}^+)|\psi\rangle =…
**Urs Schreiber:**Cosmic F- and D-strings (December 17, 2003)- In the paper Copeland, Myers, Polchinski, Cosmic F- and D-strings the authors discuss cosmic strings and F/D-strings on the same…
**Luboš:**Join the stringy discussion on news.groups (December 17, 2003)- Dear Ladies and Gentlemen! A very interesting discussion has been started at news.groups - it is a name of a…
**Arvind:**Ed’s latest (December 16, 2003)- Ed Witten’s latest: Is weakly coupled (N=4) Yang-Mills-theory also a perturbative string theory? He conjectures that it is, and…
**Urs Schreiber:**deformation of SCFTs (December 15, 2003)- This environment is very inspiring, I’ll start with a couple of questions right away: :-) Is there anything known about…
**Luboš:**Thanks to Jacques (December 15, 2003)- It seems that this string coffee table works, because you are able to see this sentence. Thanks to Jacques. So…
**Distler:**Inaugural Post (December 15, 2003)- Welcome Aaron Bergman, Robert Helling, Lubos Motl, Arvind Rajaraman and Urs Schreiber, and their brand-new blog, The String Coffee…

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