P.B. Medvedev

New Representation for String Field Solves the Consistency Problem for Open Superstring Field Theory

Abstract We modify Wittens action for the NSR superstring. Our proposal is based on the use of new “double-step” picture-changing operators. The modified action, in contrast to Wittens, generates N -point tree-level amplitudes which agree with the Koba-Nielsen amplitudes. The action is gauge invariant without any reference to a regularization and manifestly space-time supersymmetric. The algebra of the gauge transformations is closed and the classical equations of motion do not contain any picture-changing insertions.

Tachyon condensation in cubic superstring field theory

Abstract It has been conjectured that at the stationary point of the tachyon potential for the non-BPS D-brane or brane–anti-D-brane pair, the negative energy density cancels the brane tension. We study this conjecture using a cubic superstring field theory with insertion of a double-step inverse picture changing operator. We compute the tachyon potential at levels (1/2,1) and (2,6). In the first case we obtain that the value of the potential at the minimum is 97.5% of the non-BPS D-brane tension. Using a special gauge in the second case we get 105.8% of the tension.

Background formalism for superstring field theory

Abstract In the framework of the background formalism we analyse possible versions of the Witten-type NSR superstring field theory. We find the picture for string fields to be uniquely fixed by the requirement that the perturbative classical solutions are well-defined. This uniquely defined picture and the corresponding action are different from the ones in Wittens theory and coincide with the ones proposed from different reasons in our previous paper. Following the same background method we calculate the tree-level scattering amplitudes for the new action and argue that in contrast to the ones in Wittens original theory, the amplitudes are singularity-free and hence there is no need to add any tree-level counterterms. We also prove the amplitudes to reproduce correctly the first quantized results.

Tachyon solution in a cubic Neveu-Schwarz string field theory

We find a class of analytic solutions in a modified cubic theory of fermionic strings that includes the GSO(−) sector. This class contains a solution that involves a tachyon field from the GSO(−) sector and reproduces the correct value of the non-BPS D-brane tension.

Gauge invariance and tachyon condensation in cubic superstring field theory

Abstract The gauge invariance of cubic open superstring field theory is considered in a framework of level truncation, and applications to the tachyon condensation problem are discussed. As it is known, in the bosonic case the Feynman–Siegel gauge is not universal within the level truncation method. We explore another gauge that is more suitable for calculation of the tachyon potential for fermionic string at level (2,6). We show that this new gauge has no restrictions on the region of its validity at least at this level.

Neveu–Schwarz matter sliver

Abstract Using algebraic methods the Neveu–Schwarz fermionic matter sliver is constructed. Inspirited by the wedge algebra, two equations for the sliver, linear and quadratic, are considered. It is shown that both equations give the same nontrivial answer. The sliver is considered also using CFT methods where it is defined as the limit of the wedge states in the NS sector of the superstring.Using algebraic methods the Neveu-Schwarz fermionic matter sliver is constructed. Inspirited by the wedge algebra two equations for the sliver, linear and quadratic, are considered. It is shown that both equations give the same nontrivial answer. The sliver is considered also using CFT methods where it is defined as the limit of the wedge states in the NS sector of the superstring.

Chaos in M(atrix) theory

Abstract We consider the classical and quantum dynamics in M(atrix) theory. Using a simple ansatz we show that a classical trajectory exhibits a chaotic motion. We argue that the holographic feature of M(atrix) theory is related with the repulsive feature of energy eigenvalues in quantum chaotic system. Chaotic dynamics in N = 2 supersymmetric Yang—Mills theory is also discussed. We demonstrate that after the separation of “slow” and “fast” modes there is a singular contribution from the “slow” modes to the Hamiltonian of the “fast” modes.

Pure gauge configurations and solutions to fermionic superstring field theory equations of motion

Recent results on solutions to the equation of motion of the cubic fermionic string field theory and an equivalence of nonpolynomial and cubic string field theory are discussed. To have the possibility of dealing with both GSO(+) and GSO(−) sectors in the uniform way, a matrix formulation for the NS fermionic SFT is used. In constructions of analytical solutions to open-string field theories truncated pure gauge configurations parametrized by wedge states play an essential role. The matrix form of this parametrization for NS fermionic SFT is presented. Using the cubic open superstring field theory as an example we demonstrate explicitly that for the large parameter of the perturbation expansion these truncated pure gauge configurations give divergent contributions to the equations of motion on the subspace of the wedge states. The perturbation expansion is corrected by adding extra terms that are just those necessary for the equation of motion contracted with the solution itself to be satisfied.

Truncation, picture-changing operation and space time supersymmetry in Neveu-Schwarz-Ramond string field theory

Abstract The representation of the inverse picture-changing operator in terms of an appropriate truncation operator is found, which means that truncated Ramond string fields are inherent to the Witten construction. Equivalence of the Witten supertransformations and the supertransformations acting on the old truncated fields is established.

CHAOS–ORDER TRANSITION IN MATRIX THEORY

Classical dynamics in SU(2) matrix theory is investigated. A classical chaos–order transition is found. For small enough angular momentum (even for small coupling constant), the system exhibits a chaotic behavior, for large enough angular momentum, the system is regular.