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Chuan-Jie Zhu

Publications and source records attributed to Chuan-Jie Zhu.

35 records · Page 2Linked to original sources
arXiv2003

Two-Loop Superstrings in Hyperelliptic Language I: the Main Results

Following the new gauging fixing method of D'Hoker and Phong, we study two-loop superstrings in hyperelliptic language. By using hyperelliptic representation of genus 2 Riemann surface we derive a set of identities involving the Szegö kernel. These identities are used to prove the vanishing of the cosmological constant and the non-renormalization theorem point-wise in moduli space by doing the summation over all the 10 even spin structures. Modular invariance is maintained at every stage of the computation explicitly. The 4-particle amplitude is also computed and an explicit expression for the chiral integrand is obtained. We use this result to show that the perturbative correction to the $R^4$ term in type II superstring theories is vanishing at two loops. In this paper, a summary of the main results is presented with detailed derivations to be provided in two subsequent publications.

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arXiv2003

Two-Loop Superstrings in Hyperelliptic Language II: the Vanishing of the Cosmological Constant and the Non-Renormalization Theorem

The vanishing of the cosmological constant and the non-renormali-zation theorem are verified at two loops by explicit computation using the hyperelliptic language and the newly obtained chiral measure of D'Hoker and Phong. A set of identities is found which is used in the verification of the non-renormalization theorem and leads to a great simplification of the calculation of the four-particle amplitude at two loops.

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arXiv2003

Two-Loop Superstrings in Hyperelliptic Language III: the Four-Particle Amplitude

We compute explicitly the four-particle amplitude in superstring theories by using the hyperelliptic language and the newly obtained chiral measure of D'Hoker and Phong. Although the algebra of the intermediate steps is a little bit involved, we obtain a quite simple expression for the four-particle amplitude. As expected, the integrand is independent of all the insertion points. As an application of the obtained result, we show that the perturbative correction to the $R^4$ term in type II superstring theories is vanishing point-wise in (even) moduli space at two loops.

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arXiv2002

Comments on Noncommutative ADHM Construction

We extend the method of matrix partition to obtain explicitly the gauge field for noncommutative ADHM construction in some general cases. As an application of this method we apply it to the U(2) 2-instanton and get explicit result for the gauge fields in the coincident instanton limit. We also easily apply it to the noncommutative 't Hooft instantons in the appendix.

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arXiv2002

Instantons on General Noncommutative R^4

We study the U(1) and U(2) instanton solutions of gauge theory on general noncommutative $\bf{R}^4$. In all cases considered we obtain explicit results for the projection operators. In some cases we computed numerically the instanton charge and found that it is an integer, independent of the noncommutative parameters $θ_{1,2}$.

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arXiv2000

A Self-tuning Exact Solution and the Non-existence of Horizons in 5d Gravity-Scalar System

We present an exact thick domain wall solution with naked sigularities to five dimensional gravity coupled with a scalar field with exponential potential. In our solution we found exactly the special coefficient of the exponent as coming from compactification of string theory with cosmological constant. We show that this solution is self-tuning when a 3-brane is included. In searching for solution with horizon we found a similar exact solution with fine-tuned exponent coefficient with an integration constant. Failed to find a solution with horizon we prove the non-existence of horizons. These naked sigularities actually can't be resolved by horizon. We also comment on the physical relevance of this solution.}

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arXiv1999

Evidence for Nonvanishing Cosmological Constant in NonSusy Superstring Models

We reanalyse the computation of the cosmological constant $Λ$ at two loops in recently proposed Superstring models without massless gravitini, both in the theta-function based formalism and by a detailed computation in the more explicit hyperelliptic description of the underlying genus two Riemann surface. $Λ$ is expressed as the integral over the surface moduli of an amplitude which is zero if susy is not completely broken, but we find it to be nonvanishing in the susy breaking models which can be given an explicitly workable fermionic formulation. Thus unfortunately the issue of getting realistic and perturbatively viable models from Superstring Theory remains open.

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arXiv1999

An Application of the Schwarzian Derivative

In this note we present an application of the Schwarzian derivative. By exploiting some properties of the Schwarzian derivative, we solve the equation appearing in the gravity-dilaton-antisymmetric tensor system. We also mention that this method can also be used to solve some other equations.

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arXiv1999

The Complete Black Brane Solutions in D-dimensional Coupled Gravity System

In this paper, we use only the equation of motion for an interacting system of gravity, dilaton and antisymmetric tensor to study the black brane solutions. By making use of the property of Schwarzian derivative, we obtain the complete solution of this system of equations. For some special values we obtain the well-known BPS brane and black brane solutions.

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arXiv1999

Explicit Modular Invariant Two-Loop Superstring Amplitude Relevant for R^4

In this note we derive an explicit modular invariant formula for the two loop 4-point amplitude in superstring theory in terms of a multiple integral (7 complex integration variables) over the complex plane which is shown to be convergent. We consider in particular the case of the leading term for vanishing momenta of the four graviton amplitude, which would correspond to the two-loop correction of the R^4 term in the effective Action. The resulting expression is not positive definite and could be zero, although we cannot see that it vanishes.

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arXiv1999

A Study of Brane Solutions in D-dimensional Coupled Gravity System

In this paper, we use only the equation of motion for an interacting system of gravity, dilaton and antisymmetric tensor to study the soliton solutions by making use of a Poincaré invariant ansatz. We show that the system of equations are completly integrable and the solution is unique with appropriate boundary conditions. Some new class of solutions are also given explicitly.

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arXiv1995

The structure of the ground ring in critical $W_3$ gravity

By explicit calculation, I determine the structure of the ground ring of the critical $W_3$ gravity and show that there is an $su(3)$ invariant quadratic relation among the six basic elements. By using this result, I also construct some discrete physical states of the critical $W_3$ gravity.

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arXiv1993

The BRST quantization of the nonlinear $WB_2$ and $W_4$ algebras

We construct the BRST operator for the nonlinear $WB_2$ and $W_4$ algebras. Contrary to the general belief, the nilpotent condition of the BRST operator doesn't determine all the coefficients. We find a three and seven parameter family of nilpotent BRST operator for $WB_2$ and $W_4$ respectively. These free parameters are related to the canonical transformation of the ghost antighost fields.

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arXiv1992

The Complete Structure of the Cohomology Ring and Associated Symmetries in $D=2$ String Theory

We determine explicitly all structure constants of the whole chiral BRST cohomology ring in $D=2$ string theory including both the discrete states and tachyon states. This is made possible by establishing several identities for Schur polynomials with operator argument and exploring associativity. Furthermore we find that the (chiral) symmetry algebra of the charges obtained by using the descent equations can actually be read off from the cohomology ring structure by simple operation involving the ghost field $b$. We also determine the enlarged symmetry algebra which contains the charges having ghost number $-1$ and $1$. Finally the complete symmetry transformation rules are derived for closed string discrete states by carefully combining the left and right sectors. It turns out that the new states introduced recently by Witten and Zwiebach are naturally created when symmetries act on the old states.

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