50 research outputs found
Dp-D(p+4) in Noncommutative Yang-Mills
An anti-self-dual instanton solution in Yang-Mills theory on noncommutative
with an anti-self-dual noncommutative parameter is constructed. The
solution is constructed by the ADHM construction and it can be treated in the
framework of the IIB matrix model. In the IIB matrix model, this solution is
interpreted as a system of a Dp-brane and D(p+4)-branes, with the Dp-brane
dissolved in the worldvolume of the D(p+4)-branes. The solution has a parameter
that characterises the size of the instanton. The zero of this parameter
corresponds to the singularity of the moduli space. At this point, the solution
is continuously connected to another solution which can be interpreted as a
system of a Dp-brane and D(p+4)-branes, with the Dp-brane separated from the
D(p+4)-branes. It is shown that even when the parameter of the solution comes
to the singularity of the moduli space, the gauge field itself is non-singular.
A class of multi-instanton solutions is also constructed.Comment: 16 pages. v2 eq.(3.28) and typos corrected, ref. added v3 extended to
25 pages including various examples and explanations v4 misleading comments
on the instanton position are correcte
Instantons on Noncommutative R^4 and Projection Operators
I carefully study noncommutative version of ADHM construction of instantons,
which was proposed by Nekrasov and Schwarz. Noncommutative is
described as algebra of operators acting in Fock space. In ADHM construction of
instantons, one looks for zero-modes of Dirac-like operator. The feature
peculiar to noncommutative case is that these zero-modes project out some
states in Fock space. The mechanism of these projections is clarified when the
gauge group is U(1). I also construct some zero-modes when the gauge group is
U(N) and demonstrate that the projections also occur, and the mechanism is
similar to the U(1) case. A physical interpretation of the projections in IIB
matrix model is briefly discussed.Comment: 29 pages, LaTeX, no figures, further explanations on holes on branes
added, minor mistakes correcte
On the No-ghost Theorem in String Theory
We give a simple proof of the no-ghost theorem in the critical bosonic string
theory by using a similarity transformation.Comment: 5 pages, v2: a note added and a ref. added, v3: minor refinement of
wording, published versio