共查询到20条相似文献,搜索用时 31 毫秒
1.
Chandrasekhar Chatterjee Sunandan Gangopadhyay Arindam Ghosh Hazra Saurav Samanta 《International Journal of Theoretical Physics》2008,47(9):2372-2381
The appearance of non(anti)commutativity in superstring theory, satisfying the Neveu-Schwarz boundary conditions is discussed
in this paper. Both an open free superstring and also one moving in a background antisymmetric tensor field are analyzed to
illustrate the point that string non(anti)commutativity is a consequence of the nontrivial boundary conditions. The method
used here is quite different from several other approaches where boundary conditions were treated as constraints. An interesting
observation of this study is that, one requires that the bosonic sector satisfies Dirichlet boundary conditions at one end
and Neumann at the other in the case of the bosonic variables X
μ
being antiperiodic. The non(anti)commutative structures derived in this paper also leads to the closure of the super constraint
algebra which is essential for the internal consistency of our analysis. 相似文献
2.
《Physics letters. [Part B]》1988,206(4):625-630
We describe the calculation of one-loop β-functions for the Green-Schwarz heterotic superstring in a supergravity background. The calculation is considerably simplified by the use of a new set of superspace constraints. As expected, the one-loop β-functions vanish, since the constraints impose on the background the classical field equations of supergravity. 相似文献
3.
M. Chabab R. Markazi E.H. Saidi 《The European Physical Journal C - Particles and Fields》2000,13(3):543-549
Using the formal analogy between the Dick superstring inspired model and the problem of the building of an Eguchi–Hanson
metric in 4D N = 2 harmonic superspace (HS), we derive a general formula for the quark–quark interaction potential V(r) including the Dick confining potential. The interquark potential V(r) depends on the dilaton–gluon coupling and may be related to the parameterization of confinement by the quark and gluon vacuum
condensates. It is also shown how the axion field may be incorporated in agreement with 10D type IIB superstring requirements.
Others features are also discussed.
Received: 23 December 1999 / Published online: 6 March 2000 相似文献
4.
In this work we investigate the single- and the double-spin asymmetries at the collisions of polarized protons pp → (γ
*, Z
0, Z′) + X within the scope of QCD, the electroweak interaction and superstring E
6 theory. The helicity amplitude method is used. Analytical expressions for the single- and the double-spin asymmetries are
obtained and their dependence on the transverse momentum of the lepton pair is investigated at the three different values
of invariant masses of the lepton pair. The pure contribution coming from the superstring Z′ boson on the single- and double- spin asymmetries has been extracted. The results obtained allow investigation of the spin
structure of the proton. 相似文献
5.
《Physics letters. [Part B]》1986,167(2):187-190
Phenomenological constraints on the extra low-mass neutral gauge boson Z′ of present superstring models are presented and shown to imply a very fine tuning of the parameters involved in the Higgs potential. 相似文献
6.
We study the problem of a possible change in the number of constraints in linear relativistic wave equations (-iβ
μ
∂
μ
+m)ψ=0 for particles of unique mass, on introduction of minimal coupling to an external electromagnetic field. Complementing our
earlier work in which we obtained conditions for non-loss of constraints in equations characterised by the minimalβ-algebraβ
0
5 =β
0
3 we derive here the conditions for such theories not to generate more constraints than in the free case. The results are illustrated
by considering specific equations and a fallacy in certain conclusions of Kobayashi and Shamaly on this problem is pointed
out. 相似文献
7.
A space which receives covariant action is proposed for aD=10, N=1 superstring in a suitably extended configuration space having the following properties: a) a theory can be constructed dynamically
equivalent to the Green-Schwarz superstring, and b) the fermion links may be separated into types in an explicitly covariant
fashion, where the links of the first kind are irreducible.
Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 3–6. June, 1997. 相似文献
8.
Alexander Pavlov 《International Journal of Theoretical Physics》1997,36(10):2107-2113
A system with constraints is considered: a string theory whose Lagrangian is thenth power of the Gauss curvature of a space-time manifold (n∈N,n>1). The problem is solved exactly because after the constraints are utilized we deal with a variational problem with a trivial
Lagrangian, i.e., its Euler-Lagrange equations are satisfied identically. One can say that the constraints “swallow” all dynamical
degrees of freedom of the field theory. The investigation is a continuation of the 1989 work of Burlankov and Pavlov, who
solved the problem of two-dimensionalR
2-gravitation under the gauge γ=1. 相似文献
9.
Motivated by a desire to find a useful 2d Lorentz-invariant reformulation of the AdS5×S5 superstring world-sheet theory in terms of physical degrees of freedom we construct the “Pohlmeyer-reduced” version of the corresponding sigma model. The Pohlmeyer reduction procedure involves several steps. Starting with a coset space string sigma model in the conformal gauge and writing the classical equations in terms of currents one can fix the residual conformal diffeomorphism symmetry and kappa-symmetry and introduce a new set of variables (related locally to currents but non-locally to the original string coordinate fields) so that the Virasoro constraints are automatically satisfied. The resulting equations can be obtained from a Lagrangian of a non-Abelian Toda type: a gauged WZW model with an integrable potential coupled also to a set of 2d fermionic fields. A gauge-fixed form of the Pohlmeyer-reduced theory can be found by integrating out the 2d gauge field of the gauged WZW model. The small-fluctuation spectrum near the trivial vacuum contains 8 bosonic and 8 fermionic degrees of freedom with equal mass. We conjecture that the reduced model has world-sheet supersymmetry and is ultraviolet-finite. We show that in the special case of the AdS2×S2 superstring model the reduced theory is indeed supersymmetric: it is equivalent to the N=2 supersymmetric extension of the sine-Gordon model. 相似文献
10.
Kwan-Leung Chan 《Nuclear Physics B》1997,500(1-3):94-114
We systematically construct a large class of four-dimensional supersymmetric black hole solutions of toroidally compactified type IIA superstring theory by explicitly solving the Killing spinor equations. They correspond to orthogonally intersecting configurations in ten dimensions. With the Kaluza-Klein monopole, they are parameterized by four charges and preserve
of the N = 8 supersymmetry. We found a simple map to associate each charge with the corresponding Killing spinor constraints. The embedding of the N = 4 supersymmetry of a toroidally compactified heterotic string into the N = 8 supersymmetry of the IIA superstring was explicitly shown. We also found explicitly the configurations with only Ramond-Ramond charges, and those with both Neveu-Schwarz Neveu-Schwarz charges and Ramond-Ramond charges, including the dilaton and the internal metrics. The T-dual of these configurations were shown to satisfy the Killing spinor equations as well. 相似文献
11.
Conformal field theory representation and background-independent action for superstring field theory
《Nuclear Physics B》1988,310(2):428-460
The two-dimensional conformal field theory representation of Witten's open superstring field theory is discussed. We argue that the previously suggested cubic action for the superstring is actually dependent on the spacetime background, and suggest a modification which formally removes this dependence. The transformation from the new version of the superstring cubic action to Witten's action for open string states is discussed. A class of linearized solutions to the equations of motion of the open superstring cubic action are exhibited. These solutions are in one-to-one correspondence with the physical excitations (both massless and massive) of the open and closed type I superstrings. 相似文献
12.
The field equations of supersymmetric Yang–Mills theory in ten dimensions may be formulated as vanishing curvature conditions
on light-like rays in superspace. In this article, we investigate the physical content of the modified SO(7) covariant superspace constraints put forward earlier [11]. To this end, group-algebraic methods are developed which allow
to derive the set of physical fields and their equations of motion from the superfield expansion of the supercurl, systematically.
A set of integrable superspace constraints is identified which drastically reduces the field content of the unconstrained
superfield but leaves the spectrum including the original Yang–Mills vector field completely off-shell. A weaker set of constraints
gives rise to additional fields obeying first order differential equations. Geometrically, the SO(7) covariant superspace constraints descend from a truncation of Witten's original linear system to particular one-parameter
families of light-like rays.
Received: 20 April 2000 / Accepted: 10 September 2000 相似文献
13.
Ido Adam 《General Relativity and Gravitation》2009,41(4):691-705
14.
15.
16.
Canonical formalism for SO(2) is developed. This group can be seen as a toy model of the Hamilton-Dirac mechanics with constraints.
The Lagrangian and Hamiltonian are explicitly constructed and their physical interpretations are given. The Euler-Lagrange
and Hamiltonian canonical equations coincide with the Lie equations. It is shown that the constraints satisfy CCR. Consistency
of the constraints is checked.
Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005. 相似文献
17.
The group SO(6) ⊗ SO(5) is shown to be the gauge group as well as supersymmetry group of a four dimensional superstring model. Here, we discuss
how supersymmetry is realised in 4-dimensions and further, we successfully reproduce the gauge symmetry results. Using the
SO(6) ⊗ SO(5) group, all the known aspects of the string theory are obtained. The model reduces to the Standard Model which has the
capability of containing the ingredients of a successful theory of the present day physics. However, there are no Higgs in
the model. 相似文献
18.
The modified gravitational equations to describe a four-dimensional braneworld in the case with the Lorentz invariant violation
in a bulk spacetime is presented. It contains a trace part of the brane energy-momentum tensor and the coefficients of all
terms describe the Lorentz violation effects from the bulk spacetime. As an application, we apply this formalism to study
cosmology. In respect to standard effective Friedmann equations on the brane, Lorentz invariance violation in the bulk causes
a modification of this equations that can lead to significant physical consequences. In particular, the effective Friedmann
equation on the brane explicitly depends on the equation of state of the brane matter and the Lorentz violating parameters.
We show that the components of five-dimensional Weyl curvature are related to the matter on brane even at low energies. We
also find that the constraints on the theory parameters are depend on the equation of state of the energy components of the
brane matter. Finally, the stability of the model depend on the specific choices of initial conditions and the parameters
β
i
. 相似文献
19.
《Physics letters. [Part B]》1986,173(4):409-412
A gauge invariant action of free N=1 closed superstring field theory is presented using BRS charges. This action is shown to take a similar form to that of open superstring. The N=2 closed superstring is also discussed. 相似文献
20.
J. Walter C. Hartmann J. H. Maddocks 《The European physical journal. Special topics》2011,200(1):153-181
The most classic approach to the dynamics of an n-dimensional mechanical system constrained by d independent holonomic constraints is to pick explicitly a new set of (n − d) curvilinear coordinatesparametrizingthe manifold of configurations satisfying the constraints, and to compute the Lagrangian
generating the unconstrained dynamics in these (n − d) configuration coordinates. Starting from this Lagrangian an unconstrained Hamiltonian H(q,p) on 2(n−d) dimensional phase space can then typically be defined in the standard way via a Legendre transform. Furthermore, if the
system is in contact with a heat bath, the associated Langevin and Fokker-Planck equations can be introduced. Provided that
an appropriate fluctuation-dissipation condition is satisfied, there will be a canonical equilibrium distribution of the Gibbs
form exp(−βH) with respect to the flat measure dqdp in these 2(n − d) dimensional curvilinear phase space coordinates. The existence of (n − d) coordinates satisfying the constraints is often guaranteed locally by an implicit function theorem. Nevertheless in many
examples these coordinates cannot be constructed in any tractable form, even locally, so that other approaches are of interest.
In ambient space formulations the dynamics are defined in the full original n-dimensional configuration space, and associated 2n-dimensional phase space, with some version of Lagrange multipliers introduced so that the 2(n − d) dimensional sub-manifold of phase space implied by the holonomic constraints and their time derivative, is invariant under
the dynamics. In this article we review ambient space formulations, and explain that for constrained dynamics there is in
fact considerable freedom in how a Hamiltonian form of the dynamics can be constructed. We then discuss and contrast the Langevin
and Fokker-Planck equations and their equilibrium distributions for the different forms of ambient space dynamics. 相似文献