இழை 2
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Extra dimensions. String theory requires a definite number of spacetime
dimensions, ten.2 The field equations have solutions with four
large flat and six small curved dimensions, with four-dimensional
physics that resembles the Standard Model.
5. Supersymmetry. Consistent string theories require spacetime supersymmetry,
as either a manifest or a spontaneously broken symmetry
-------------------------------------
Volume one is an introduction to bosonic string theory. This is not a
realistic theory — it does not have fermions, and as far as is known has no
stable ground state. The philosophy here is the same as in starting a course
on quantum field theory with a thorough study of scalar field theory.
----------------
weyl algebra
non commutative algebra
------------------------
D-brane in the type I, IIA, and IIB string theories, a dynamical object on
which strings can end. The term is a contraction of Dirichlet brane. The
coordinates of the attached strings satisfy Dirichlet boundary conditions
in the directions normal to the brane and Neumann conditions in the
directions tangent to the brane. A Dp-brane is p-dimensional, with p taking
any even value in the IIA theory, any odd value in the IIB theory, and
the values 1, 5, and 9 in the type I theory; a D9-brane fills space and so
corresponds to an ordinary Neumann boundary condition. The Dp-brane
is a source for the (p + 1)-form R–R gauge field. The mass or tension
of a D-brane is intermediate between that of an ordinary quantum or a
fundamental string and that of a soliton. The low energy fluctations of Dbranes
are described by supersymmetric gauge theory, which is non-Abelian
for coincident branes.
0000000000000000000000000000000000000000000
Planck length the natural length scale of quantum gravity, LP = M−1
P = 1.6 ×
10−33 cm, constructed from ¯h, c, and GN.
Planck mass the natural mass scale of quantum gravity, MP = 1.22×1019 GeV,
constructed from ¯h, c, and GN.
000000000000000000000000000000000000000000000
--------------
Extra dimensions. String theory requires a definite number of spacetime
dimensions, ten.2 The field equations have solutions with four
large flat and six small curved dimensions, with four-dimensional
physics that resembles the Standard Model.
5. Supersymmetry. Consistent string theories require spacetime supersymmetry,
as either a manifest or a spontaneously broken symmetry
-------------------------------------
Volume one is an introduction to bosonic string theory. This is not a
realistic theory — it does not have fermions, and as far as is known has no
stable ground state. The philosophy here is the same as in starting a course
on quantum field theory with a thorough study of scalar field theory.
----------------
weyl algebra
non commutative algebra
------------------------
D-brane in the type I, IIA, and IIB string theories, a dynamical object on
which strings can end. The term is a contraction of Dirichlet brane. The
coordinates of the attached strings satisfy Dirichlet boundary conditions
in the directions normal to the brane and Neumann conditions in the
directions tangent to the brane. A Dp-brane is p-dimensional, with p taking
any even value in the IIA theory, any odd value in the IIB theory, and
the values 1, 5, and 9 in the type I theory; a D9-brane fills space and so
corresponds to an ordinary Neumann boundary condition. The Dp-brane
is a source for the (p + 1)-form R–R gauge field. The mass or tension
of a D-brane is intermediate between that of an ordinary quantum or a
fundamental string and that of a soliton. The low energy fluctations of Dbranes
are described by supersymmetric gauge theory, which is non-Abelian
for coincident branes.
0000000000000000000000000000000000000000000
Planck length the natural length scale of quantum gravity, LP = M−1
P = 1.6 ×
10−33 cm, constructed from ¯h, c, and GN.
Planck mass the natural mass scale of quantum gravity, MP = 1.22×1019 GeV,
constructed from ¯h, c, and GN.
000000000000000000000000000000000000000000000
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