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Vanadium dioxide (VO2) is a well-known phase-changing material that goes from a semiconducting state to a metallic one at a critical temperature of 68 °C, which is the closest to room temperature (25 °C). The electrical transition is also accompanied by structural and optical changes. The optical transition upon heating-also known as thermochromism-makes VO2 a possible coating for “intelligent” windows. In this work, the relationship between the thermochromic performance of VO2 films and the surface morphology was investigated using Temperature-dependent Atomic Force Microscopy (T-AFM) in conjunction with the X-ray Diffraction technique and Scanning Electron Microscopy. In particular, VO2 films were deposited using the rf sputtering technique on Silicon and glass substrates at a substrate temperature of 300 °C, which is one of the lowest for this technique to grow the thermochromic monoclinic phase of VO2. It was found that upon heating (25–100 °C), there was a decrease in RMS roughness for all films independent from the substrate; the value of RMS roughness, however, varied depending on the substrate. Finally, the thermochromic parameters of the VO2 films were correlated with the surface morphology and appeared to be dependent on the kind of substrate used.

We present a new approach to formulating open superstring field theory based on the covering of the supermoduli space of super-Riemann surfaces and explicitly construct a gauge-invariant action in the Neveu-Schwarz sector up to quartic interactions. The cubic interaction takes a form of an integral over an odd modulus of disks with three punctures and the associated ghost is inserted. The quartic interaction takes a form of an integral over one even modulus and two odd moduli, and it can be interpreted as the integral over the region of the supermoduli space of disks with four punctures which is not covered by Feynman diagrams with two cubic vertices and one propagator. As our approach is based on the covering of the supermoduli space, the resulting theory naturally realizes an $A_\infty$ structure, and the two-string product and the three-string product used in defining the cubic and quartic interactions are constructed to satisfy the $A_\infty$ relations to this order., Comment: 60 pages, 3 figures; v2: minor corrections and references added; v3: a proof that the quartic vertex is unambiguously defined for general off-shell states added in appendix A.5, version published in JHEP

International audience; Long poly-diacetylene chains are excellent candidates for planar, on-surface synthesizedmolecular electronic wires. Since hexagonal-Boron Nitride (h-BN) was identified as the bestavailable atomically flat insulator for the deposition of poly-diacetylene precursors, we demonstratethe polymerization patterns and rate on it under UV-light irradiation, with subsequent polymeridentification by atomic force microscopy. The results on h-BN indicate self-sensitization whichyields blocks comprised of several polymers, unlike on the well-studied graphite/diacetylene system,where the polymers are always isolated. In addition, the photo-polymerization proceeds at least170 times faster on h-BN, where it also results in longer polymers. Both effects are explained bythe h-BN bandgap, which is larger than the diacetylene electronic excitation energy, thus allowingthe transfer of excess energy absorbed by polymerized wires to adjacent monomers, triggeringtheir polymerization. This work sets the stage for conductance measurements of single molecularpoly-diacetylene wires on h-BN.

cited By 1; International audience; Single crystal sapphire and diamond surfaces are used as planar, atomically flat insulating surfaces, for the deposition of the diacetylene compound 10,12-nonacosadiynoic acid. The surface assembly is compared with results on hexagonal boron nitride (h-BN), highly oriented pyrolytic graphite (HOPG) and MoS2 surfaces. A perfectly flat-lying monolayer of 10,12-nonacosadiynoic acid self-assembles on h-BN like on HOPG and MoS2. On sapphire and oxidized diamond surfaces, we observed assemblies of standing-up molecular layers. Surface assembly is driven by surface electrostatic dipoles. Surface polarity is partially controlled using a hydrogenated diamond surface or totally screened by the deposition of a graphene layer on the sapphire surface. This results in a perfectly flat and organized SAM on graphene, which is ready for on-surface polymerization of long and isolated molecular wires under ambient conditions.

We construct a gauge invariant action for the Neveu-Schwarz and Ramond sectors of open superstring field theory realizing a cyclic $A_\infty$ structure, providing the first complete and fully explicit solution to the classical Batalin-Vilkovisky master equation in superstring field theory. We also demonstrate the equivalence of our action to the Wess-Zumino-Witten-based construction of Kunitomo and one of the authors., 41 pages, added discussion of PCO in subsection 3.1

To realize novel nanodevices beyond today's silicon-based transistors, a method is needed that will allow us to create nanowires at designated positions. In this review article, we introduce our method for creating a conjugated polymer nanowire by initiating a chain polymerization of organic molecules using the tip of a scanning tunneling microscope. We have demonstrated this method using a self-ordered monomolecular layer of amphiphilic diacetylene compound adsorbed on a graphite surface. The termination of the chain polymerization can also be controlled by making an artificial defect in advance. [DOI: 10.1380/ejssnt.2004.99]

The chain polymerization in a monomolecular layer of unsaturated organic compounds on a surface is investigated using a scanning tunneling microscope (STM). We used self-ordered layers of 10,12-pentacosadiynoic acid or 10,12-nonacosadiynoic acid of diacetylene compounds on a graphite substrate. Ultraviolet light irradiation on the molecular layer induced the chain polymerization, and the created polymers can be clearly imaged by STM. The tunneling electrons from an STM tip can also excite a molecule, and the excited molecule initiates the extended chain reaction. The termination of chain reaction can also be controlled by making an artificial defect in advance using an STM tip. As a result, we can control the initiation and termination of chain polymerization with a spatial precision of the order of 1 nm.

cited By 14; International audience; Bottom-up creation of huge molecular complexes by covalently interconnecting functional molecules and conductive polymers is a key technology for constructing nanoscale electronic circuits. In this study, we have created an array of molecule–polymer nanojunctions from C60 molecules and polydiacetylene (PDA) nanowires at designated positions on solid surfaces by controlling self-assemblies and intermolecular chemical reactions of molecular ingredients predeposited onto the surfaces. In the proposed method, the construction of each nanojunction spontaneously proceeds via two types of chemical reactions: a chain polymerization among self-assembled diacetylene compound molecules for creating a single PDA nanowire and a subsequent cycloaddition reaction between the propagating forefront part of the PDA backbone and a single C60 molecule adsorbed on the surface. Scanning tunneling microscopy has proved that the C60 molecule is covalently connected to each end of the π-conjugated PDA backbone. Furthermore, the decrease in the energy gap of the C60 molecule in nanojunctions is observed as compared with that of pristine C60 molecules, which is considered to be due to the covalent interaction between the PDA edge and the C60 molecule.

The one-loop effective action for general trajectories of D-particles in Matrix theory is calculated in the expansion with respect to the number of derivatives up to six, which gives the equation of motion consistently. The result shows that the terms with six derivatives vanish for straight-line trajectories, however, they do not vanish in general. This provides a concrete example that non-renormalization of twelve-fermion terms does not necessarily imply that of six-derivative terms., 18 pages, LaTeX2e, no figures, v2: a coefficient in (3.32) and the corresponding one in (3.33) corrected and a minor change

A (–Cu–O–) string on a Ag(110) surface defined by scanning tunneling microscopy (STM) was studied using the x-ray photoelectron spectroscopy (XPS), high resolution electron energy loss spectroscopy (HREELS). These data give the information about bonding properties which cannot be derived from the STM images. The combinative studies could show the structure as well as the growth mechanism of (–Cu–O–) strings on the Ag(110) surface. Deposition of Cu atoms on a p(2×1)-O Ag(110) surface resulted in a new O(1s) peak at 529.9 eV in the XPS and a new electron energy loss peak at 35 meV in the HREELS. These new peaks are assignable to the (Cu–O) bonding state on Ag(110), which is corresponding to the growth of new (–Cu–O–) strings in the [110] direction shown by the STM. These results suggest a stoichiometric reaction producing (–Cu–O–) strings according to an equation of (–Ag–O–)+Cu→(–Cu–O–)+Ag on the Ag(110) surface. The fact that the Ag atoms released by the chemical reaction make layered Ag islands and the (...

The Berkovits formulation of open superstring field theory is based on the large Hilbert space of the superconformal ghost sector. We discuss its relation to the Witten formulation based on the small Hilbert space. We introduce a one-parameter family of conditions for partial gauge fixing of the Berkovits formulation such that the cubic interaction of the theory under the partial gauge fixing reduces to that of the Witten formulation in a singular limit. The local picture-changing operator at the open-string midpoint in the Witten formulation is regularized in our approach, and the divergence in on-shell four-point amplitudes coming from collision of picture-changing operators is resolved. The quartic interaction inherited from the Berkovits formulation plays a role of adjusting different behaviors of the picture-changing operators in the $s$ channel and in the $t$ channel of Feynman diagrams with two cubic vertices, and correct amplitudes in the world-sheet theory are reproduced. While gauge invariance at the second order in the coupling constant is obscured in the Witten formulation by collision of picture-changing operators, it is well defined in our approach and is recovered by including the quartic interaction inherited from the Berkovits formulation., Comment: 50 pages, 2 figures; v2: references added, minor changes, version published in JHEP

We construct a complete action for open superstring field theory that includes the Neveu-Schwarz sector and the Ramond sector. For the Neveu-Schwarz sector, we use the string field in the large Hilbert space of the superconformal ghost sector, and the action in the Neveu-Schwarz sector is the same as the Wess-Zumino-Witten-like action of the Berkovits formulation. For the Ramond sector, it is known that the BRST cohomology on an appropriate subspace of the small Hilbert space reproduces the correct spectrum, and we use the string field projected to this subspace. We show that the action is invariant under gauge transformations that are consistent with the projection for the string field in the Ramond sector.

The WZW form of open superstring field theory has linearized gauge invariances associated with the BRST operator Q and the zero mode η [subscript 0] of the picture minus-one fermionic superconformal ghost. We discuss gauge fixing of the free theory in a simple class of gauges using the Faddeev-Popov method. We find that the world-sheet ghost number of ghost and antighost string fields ranges over all integers, except one, and at any fixed ghost number, only a finite number of picture numbers appear. We calculate the propagators in a variety of gauges and determine the field-antifield content and the free master action in the Batalin-Vilkovisky formalism. Unlike the case of bosonic string field theory, the resulting master action is not simply related to the original gauge-invariant action by relaxing the constraint on the ghost and picture numbers., United States. Dept. of Energy (Cooperative rRsearch Agreement DE-FG02-05ER41360.)

The level-truncation analysis of open string field theory for a class of periodic marginal deformations indicates that a branch of solutions in Siegel gauge exists only for a finite range of values of the marginal field. The periodicity in the deformation parameter is thus obscure. We use the relation between gauge-invariant observables and the closed string tadpole on a disk conjectured by Ellwood to construct a map between the deformation parameter of the boundary conformal field theory and the parameter labeling classical solutions of open string field theory. We evaluate the gauge-invariant observables for the numerical solutions in Siegel gauge up to level 12 and find that our results qualitatively agree with the analysis by Sen using the energy-momentum tensor and are consistent with the picture that the finite range of the branch covers one fundamental domain of the periodic moduli space., Comment: 27 pages, 15 figures; v2: references added, minor changes, version published in JHEP

We construct analytic solutions of open string field theory using boundary condition changing (bcc) operators. We focus on bcc operators with vanishing conformal weight such as those for regular marginal deformations of the background. For any Fock space state phi, the component string field of the solution Psi exhibits a remarkable factorization property: it is given by the matter three-point function of phi with a pair of bcc operators, multiplied by a universal function that only depends on the conformal weight of phi. This universal function is given by a simple integral expression that can be computed once and for all. The three-point functions with bcc operators are thus the only needed physical input of the particular open string background described by the solution. We illustrate our solution with the example of the rolling tachyon profile, for which we prove convergence analytically. The form of our solution, which involves bcc operators instead of explicit insertions of the marginal operator, can be a natural starting point for the construction of analytic solutions for arbitrary backgrounds., Comment: 21 pages, 1 figure, LaTeX2e; v2: minor changes, version published in JHEP

We develop a calculable analytic approach to marginal deformations in open string field theory using wedge states with operator insertions. For marginal operators with regular operator products, we construct analytic solutions to all orders in the deformation parameter. In particular, we construct an exact time-dependent solution that describes D-brane decay and incorporates all alpha' corrections. For marginal operators with singular operator products, we construct solutions by regularizing the singularity and adding counterterms. We explicitly carry out the procedure to third order in the deformation parameter., Comment: 34 pages, LaTeX2e, 1 figure; v2: minor corrections, version published in JHEP

We construct analytic solutions of open superstring field theory for any exactly marginal deformation in any boundary superconformal field theory when properly renormalized operator products of the marginal operator are given. Our construction is an extension of the general framework for marginal deformations developed in arXiv:0707.4472 for open bosonic string field theory, and the solutions are based on integrated vertex operators which are closely related to finite deformations in boundary superconformal field theory., 25 pages, no figures, LaTeX2e

We extend the calculable analytic approach to marginal deformations recently developed in open bosonic string field theory to open superstring field theory formulated by Berkovits. We construct analytic solutions to all orders in the deformation parameter when operator products made of the marginal operator and the associated superconformal primary field are regular., Comment: 17 pages, no figures; v2: the discussion on the reality condition corrected and expanded, a note on solutions satisfying the reality condition added; v3: a typo in (6.3) corrected, a reference added, minor changes

We construct analytic solutions of open bosonic string field theory for any exactly marginal deformation in any boundary conformal field theory when properly renormalized operator products of the marginal operator are given. We explicitly provide such renormalized operator products for a class of marginal deformations which include the deformations of flat D-branes in flat backgrounds by constant massless modes of the gauge field and of the scalar fields on the D-branes, the cosine potential for a space-like coordinate, and the hyperbolic cosine potential for the time-like coordinate. In our construction we use integrated vertex operators, which are closely related to finite deformations in boundary conformal field theory, while previous analytic solutions were based on unintegrated vertex operators. We also introduce a modified star product to formulate string field theory around the deformed background., 63 pages, 10 figures, LaTeX2e

Schnabl recently constructed an analytic solution for tachyon condensation in Witten's open string field theory. The solution consists of two pieces. Only the first piece is involved in proving that the solution satisfies the equation of motion when contracted with any state in the Fock space. On the other hand, both pieces contribute in evaluating the kinetic term to reproduce the value predicted by Sen's conjecture. We therefore need to understand why the second piece is necessary. We evaluate the cubic term of the string field theory action for Schnabl's solution and use it to show that the second piece is necessary for the equation of motion contracted with the solution itself to be satisfied. We also present the solution in various forms including a pure-gauge configuration and provide simpler proofs that it satisfies the equation of motion., 33 pages, 4 figures, LaTeX2e; v2: minor changes, version published in JHEP

We show that vacuum string field theory with the singular kinetic operator conjectured by Gaiotto, Rastelli, Sen and Zwiebach can be obtained by field redefinition from a regular theory constructed by Takahashi and Tanimoto. We solve the equation of motion both by level truncation and by a series expansion using the regulated butterfly state, and we find evidence that the energy density of a D25-brane is well defined and finite. Although the equation of motion naively factorizes into the matter and ghost sectors in the singular limit, subleading terms in the kinetic operator are relevant and the factorization does not strictly hold. Nevertheless, solutions corresponding to different D-branes can be constructed by changing the boundary condition in the boundary conformal field theory formulation of string field theory, and ratios of D-brane tensions are shown to be reproduced correctly., Comment: 31 pages, 1 figure, LaTeX2e; v2: one reference added, minor changes

We complete the construction of the Neveu-Schwarz sector of heterotic string field theory begun in hep-th/0406212 by giving a closed-form expression for the action and gauge transformations. Just as the Wess-Zumino-Witten (WZW) action for open superstring field theory can be constructed from pure-gauge fields in bosonic open string field theory, our heterotic string field theory action is constructed from pure-gauge fields in bosonic closed string field theory. The construction involves a simple alternative form of the WZW action which is consistent with the algebraic structures of closed string field theory., 22 pages, no figures, LaTeX2e

We construct the Neveu-Schwarz sector of heterotic string field theory using the large Hilbert space of the superghosts and the multi-string products of bosonic closed string field theory. No picture-changing operators are required as in Wess-Zumino-Witten-like open superstring field theory. The action exhibits a novel kind of nonpolynomiality: in addition to terms necessary to cover missing regions of moduli spaces, new terms arise from the boundary of the missing regions and its subspaces. We determine the action up to quintic order and a subset of terms to all orders., 15 pages, no figures, LaTeX2e; v2: minor cosmetic changes

We solve the equation of motion of Witten's cubic open string field theory in a series expansion using the regulated butterfly state. The expansion parameter is given by the regularization parameter of the butterfly state, which can be taken to be arbitrarily small. Unlike the case of level truncation, the equation of motion can be solved for an arbitrary component of the Fock space up to a positive power of the expansion parameter. The energy density of the solution is well-defined and remains finite even in the singular butterfly limit, and it gives approximately 68% of the D25-brane tension for the solution at the leading order. Moreover, it simultaneously solves the equation of motion of vacuum string field theory, providing support for the conjecture at this order. We further improve our ansatz by taking into account next-to-leading terms, and find two numerical solutions which give approximately 88% and 109%, respectively, of the D25-brane tension for the energy density. These values are interestingly close to those by level truncation at level 2 without gauge fixing studied by Rastelli and Zwiebach and by Ellwood and Taylor., 38 pages, no figures, LaTeX2e; v2: the footnote on hep-th/0302151 changed and moved to the introduction; v3: minor typos corrected, published version

Noncommutative Chern-Simons theory can be classically mapped to commutative Chern-Simons theory by the Seiberg-Witten map. We provide evidence that the equivalence persists at the quantum level by computing two and three-point functions of field strengths on the commutative side and their Seiberg-Witten transforms on the noncommutative side to the first nontrivial order in perturbation theory., Comment: 28 pages, 8 figures, 15 eps files, LaTeX2e; v2: a comment and references added in the discussion

We propose a description of open string fields on a D25-brane in vacuum string field theory. We show that the tachyon mass is correctly reproduced from our proposal and further argue that the mass spectrum of all other open string states is correctly obtained as well. We identify the string coupling constant from the three-tachyon coupling and show that the tension of a D25-brane is correctly expressed in terms of the coupling constant, which resolves the controversy in the literature. We also discuss a reformulation of our description which is rather similar to boundary string field theory., 54 pages (main part: 27 pages), 1 figure, LaTeX2e; v2: an analytic evaluation of the integral I_{3/2} in Appendix D, a reference added, minor changes, to appear in JHEP

We derive an exact expression for the Seiberg-Witten map of noncommutative gauge theory. It is found by studying the coupling of the gauge field to the Ramond-Ramond potentials in string theory. Our result also proves the earlier conjecture by Liu., Comment: 20 pages, LaTeX2e; v2: references added, typos corrected; v3: The proof improved. (The gauge theory proof of the Seiberg-Witten map is separated from discussion of its string theory origin.) References added. Version to appear in Phys. Rev. D

Polymer industries depend on the spontaneous polymerization of molecules into chains in response to an appropriate trigger. We have succeeded in inducing and guiding chain polymerization over tiny distances, initiating and terminating linear propagation at any chosen point to a spatial precision of about 1 nm by using the probe tip of a scanning tunnelling microscope. Being able to exert such fine control over nanoscale fabrication and interconnection should help to take molecular nanoelectronics beyond the present silicon-based-device technology.

We study coupling of noncommutative gauge theories on branes to closed string in the bulk. We derive an expression for the gauge theory operator dual to the bulk graviton, both in bosonic string theory and superstring theory. In either case, we find that the coupling is different from what was expected in the literature when the graviton is polarized in the noncommutative directions. In the case of superstring, the expression for the energy-momentum tensor is consistent with the way the bulk metric appears in the action for the noncommutative gauge theory. We also clarify some aspects of the correspondence between operators in the gauge theory and boundary conditions in the dual gravitational description., 31 pages, LaTeX2e; v2: a new section on superstring added; v3: typos corrected, version to appear in Nucl. Phys. B

It was argued that there are two different descriptions of the effective Lagrangian of gauge fields on D-branes by non-commutative gauge theory and by ordinary gauge theory in the presence of a constant B field background. In the case of bosonic string theory, however, it was found in the previous works that the two descriptions are incompatible under the field redefinition which relates the non-commutative gauge field to the ordinary one found by Seiberg and Witten. In this paper we resolve this puzzle to observe the necessity of gauge-invariant but B-dependent correction terms involving metric in the field redefinition which have not been considered before. With the problem resolved, we establish a systematic method under the alpha' expansion to derive the constraints on the effective Lagrangian imposed by the compatibility of the two descriptions where the form of the field redefinition is not assumed., 39 pages, LaTeX2e, no figures; v2: Appendix B corrected, minor changes; v3: Abstract, Introduction and Section 5 revised to emphasize our new results, minor changes, references updated, version to be published in Nucl. Phys. B

We consider the constraints on the effective Lagrangian of the rank-one gauge field on D-branes imposed by the equivalence between the description by ordinary gauge theory and that by non-commutative gauge theory in the presence of a constant B field. It is shown that we can consistently construct the two-derivative corrections to the Dirac-Born-Infeld Lagrangian up to the quartic order of field strength and the most general form which satisfies the constraints up to this order is derived., Comment: 20 pages, LaTeX2e, no figures; v2: (foot)notes added including an important one at the end of the paper, minor corrections, to appear in Nucl. Phys. B

As a continuation of our previous work on the multi-body forces of D-particles in supergravity and Matrix theory, we investigate the problem of motion. We show that the scattering of D-particles including recoil derived in Matrix theory is precisely reproduced by supergravity with the discrete light-cone prescription up to the second order in 11 dimensional Newton constant. An intimate connection of recoil and Galilei invariance in supergravity is pointed out and elucidated., 19 pages, no figures, LaTeX

We present detailed analyses of the 3-body interactions of D-particles from both sides of 11 dimensional supergravity and Matrix theory. In supergravity, we derive a complete expression for the classical bosonic effective action for D-particles including 2-and 3-body interaction terms. In Matrix theory, we compute 1-particle irreducible contributions to the eikonal phase shift in the two-loop approximation. The results precisely agree with the predictions from supergravity and thus provide a strong support to the discrete light-cone interpretation of the Matrix-theory conjecture as a possible nonperturbative definition of M-theory., 38 pages, no figures, a few minor typos are corrected

We discuss a T-duality transformation for the c=1/2 matrix model for the purpose of studying duality transformations in a possible toy example of nonperturbative frameworks of string theory. Our approach is to first investigate the scaling limit of the Schwinger-Dyson equations and the stochastic Hamiltonian in terms of the dual variables and then compare the results with those using the original spin variables. It is shown that the c=1/2 model in the scaling limit is T-duality symmetric in the sphere approximation. The duality symmetry is however violated when the higher-genus effects are taken into account, owing to the existence of global Z_2 vector fields corresponding to nontrivial homology cycles. Some universal properties of the stochastic Hamiltonians which play an important role in discussing the scaling limit and have been discussed in a previous work by the last two authors are refined in both the original and dual formulations. We also report a number of new explicit results for various amplitudes containing macroscopic loop operators., Comment: RevTex, 46 pages, 5 eps figures

We present a new class of matrix models which are manifestly symmetric under the T-duality transformation of the target space. The models may serve as a nonperturbative regularization for the T-duality symmetry in continuum string theory. In particular, it now becomes possible to extract winding modes explicitly in terms of extended matrix variables., Comment: REVTeX, 15 pages, no figures

not Available.

We construct analytic solutions for marginal deformations satisfying the reality condition in open superstring field theory formulated by Berkovits when operator products made of the marginal operator and the associated superconformal primary field are regular. Our strategy is based on the recent observation by Erler that the problem of finding solutions for marginal deformations in open superstring field theory can be reduced to a problem in the bosonic theory of finding a finite gauge parameter for a certain pure-gauge configuration labeled by the parameter of the marginal deformation. We find a gauge transformation generated by a real gauge parameter which infinitesimally changes the deformation parameter and construct a finite gauge parameter by its path-ordered exponential. The resulting solution satisfies the reality condition by construction., The Seitaro Nakamura Prize awarded, 16 pages, no figures; v2: a note on different conventions for the conjugation associated with the reality condition added, references added, minor changes

We consider twisted tachyons on C/Z_N orbifolds of bosonic closed string theory. It has been conjectured that these tachyonic instabilities correspond to decays of the orbifolds into flat space or into orbifolds with smaller deficit angles. We examine this conjecture using closed string field theory, with the string field truncated to low-level tachyons. We compute the tachyon potentials for C/Z_2 and C/Z_3 orbifolds and find critical points at depths that generate about 70% of the expected change in the deficit angle. We find that both twisted fields and untwisted modes localized near the apex of the cone acquire vacuum expectation values and contribute to the potential., 36 pages, 5 figures, LaTeX2e; v2: one reference added and minor cosmetic changes

The twisted butterfly state solves the equation of motion of vacuum string field theory in the singular limit. The finiteness of the energy density of the solution is an important issue, but possible conformal anomaly resulting from the twisting has prevented us from addressing this problem. We present a description of the twisted regulated butterfly state in terms of a conformal field theory with a vanishing central charge which consists of the ordinary bc ghosts and a matter system with c=26. Various quantities relevant to vacuum string field theory are computed exactly using this description. We find that the energy density of the solution can be finite in the limit, but the finiteness depends on the subleading structure of vacuum string field theory. We further argue, contrary to our previous expectation, that contributions from subleading terms in the kinetic term to the energy density can be of the same order as the contribution from the leading term which consists of the midpoint ghost insertion., 36 pages, no figures, LaTeX2e; v2: minor corrections; v3: typos corrected, published in JHEP; v4: a minor typo in (C.12) corrected