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- Cederwall, Martin, 1961, et al.
(författare)
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Deformations in closed string theory - canonical formulation and regularization
- 1995
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Ingår i: Nucl.Phys. B464 (1996) 117.
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Tidskriftsartikel (refereegranskat)abstract
- We study deformations of closed string theory by primary fields of conformal weight (1,1), using conformal techniques on the complex plane. A canonical surface integral formalism for computing commutators in a non-holomorphic theory is constructed, and explicit formulae for deformations of operators are given. We identify the unique regularization of the arising divergences that respects conformal invariance, and consider the corresponding parallel transport. The associated connection is metric compatible and carries no curvature.
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| 2. |
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| 3. |
- Sundell, Per, 1966
(författare)
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Vertex Operators, String Vertices and Conformal Field Theory Deformations
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We compute multi-string interaction vertices by sewing of basic string interaction vertex operators, so called dual Reggeon vertex operators. These operators describe the interaction between two complete external string sectors. They are particularly useful when the interactions involve twisted sectors. In paper I we check the dual vertex formalism by sewing multi-loop interactions in the bosonic string. We also construct the dual Reggeon vertex describing the interaction between a twisted and an untwisted bosonic string sektor. In papers II to IV we compute the string interaction vertex describing the interaction between two twisted fermion sectors of the RNS string. Nearby conformal field theories can be connected by so called marginal deformations. Papers V and VI deal with the regularization of such marginal deformations and the construction of connections on spaces of conformal field theories. The papers I to VI concern various aspects of string field theory. Sewing of Reggeon vertex operators may be thought of as interactions between second quantized strings fields. The spaces of conformal field theories may be thought of as the spaces of classical solutions to a string field action. In the introductory text we therefore provide some background material on conformal field theory and string field theory.
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| 5. |
- Telaretti Leggieri, Rosella, et al.
(författare)
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Polyester–melamine coil coating formulation reinforced with surface-modified cellulose nanofibrils
- 2023
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Ingår i: Progress in organic coatings. - : Elsevier B.V.. - 0300-9440 .- 1873-331X. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- In light of the need to redesign industrially produced materials by utilizing renewable resources, nanoscopic forms of cellulose are regarded as a valuable asset. In this work, the potential of cellulose nanofibrils (CNFs) as an unconventional nanoadditive for a polyester–melamine coil coating formulation is explored. CNFs, hydrophilic nanomaterials with high aspect ratios, were successfully incorporated in the solvent-borne formulation. Coatings were prepared with extremely low loadings of the nanoadditive (0.5 and 0.7 wt%). At these concentrations, the volume fraction of the nanofibrils in the coatings was calculated to be close to their percolation threshold. Two different pathways of CNF surface modification were applied to allow for a good compatibilization in the resin matrix, and the formulations were cured in two different settings. The effective compatibilization of the nanoadditive led to a significant variation of the viscoelastic properties in the coatings containing CNFs. The results from dynamic mechanical analysis (DMA) highlighted the effect of CNFs on the crosslinked network at the nanoscale, resulting in an increase in Tg. Additionally, an increase in the stress at break and Young's modulus was determined by tensile testing, while satisfactory elongation at break was preserved. Other relevant effects induced by the presence of CNFs on the properties of the coatings were highlighted, such as a significant matt effect, increased surface roughness and lower scratch resistance. A preliminary evaluation of the water barrier properties by electrochemical impedance spectroscopy (EIS) is also presented, suggesting that the incorporation of a hydrophilic nanoadditive did not lead to a deterioration of the coatings' performance. © 2023 The Authors
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