The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
H. G. Ganev - One of the best experts on this subject based on the ideXlab platform.
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The proton-neutron symplectic model of nuclear collective motions
Journal of Physics: Conference Series, 2016Co-Authors: H. G. GanevAbstract:The proton-neutron symplectic model of nuclear collective motion is presented. It is shown that it appears as a natural multi-major-Shell Extension of the generalized proton- neutron SU(3) scheme which includes rotations with intrinsic vortex as well as monopole, quadrupole and dipole giant resonance vibrational degrees of freedom.
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Shell-model representations of the proton-neutron symplectic model
The European Physical Journal A, 2015Co-Authors: H. G. GanevAbstract:The representation theory of the recently introduced proton-neutron symplectic model in the many-particle Hilbert space is considered. The relation of the Sp (12, R ) irreducible representations (irreps) with the Shell-model classification of the basis states is considered by extending of the state space to the direct product space of SU _ p (3) ⊗ SU _ n (3) irreps, generalizing in this way the Elliott’s SU (3) model for the case of two-component system. The Sp (12, R ) model appears then as a natural multi-major-Shell Extension of the generalized proton-neutron SU (3) scheme, which takes into account the core collective excitations of monopole and quadrupole, as well as dipole type associated with the giant resonance vibrational degrees of freedom. Each Sp (12, R ) irreducible representation is determined by a symplectic bandhead or an intrinsic U (6) space which can be fixed by the underlying proton-neutron Shell-model structure, so the theory becomes completely compatible with the Pauli principle. It is shown that this intrinsic U (6) structure is of vital importance for the appearance of the low-lying collective bands without involving a mixing of different symplectic irreps. The full range of low-lying collective states can then be described by the microscopically based intrinsic U (6) structure, renormalized by coupling to the giant resonance vibrations.
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The proton-neutron symplectic model of nuclear collective motions
arXiv: Nuclear Theory, 2014Co-Authors: H. G. GanevAbstract:A proton-neutron symplectic model of collective motions, based on the non-compact symplectic group $Sp(12,R)$, is introduced by considering the symplectic geometry of the two-component many-particle nuclear system. The possible classical collective motions are determined by different dynamical groups that can be constructed from the symplectic generators. The relation of the $Sp(12,R)$ irreps with the Shell-model classification of the basis states is considered by extending of the state space to the direct product space of $SU_{p}(3) \otimes SU_{n}(3)$ irreps, generalizing in this way the Elliott's $SU(3)$ model for the case of two-component system. The $Sp(12,R)$ model appears then as a natural multi-major-Shell Extension of the generalized proton-neutron $SU(3)$ scheme which takes into account the core collective excitations of monopole and quadrupole, as well as dipole type associated with the giant resonance vibrational degrees of freedom. Each $Sp(12,R)$ irreducible representation is determined by a symplectic bandhead or an intrinsic $U(6)$ space which can be fixed by the underlying proton-neutron Shell-model structure, so the theory becomes completely compatible with the Pauli principle. It is shown that this intrinsic $U(6)$ structure is of vital importance for the appearance of the low-lying collective bands with both the positive and negative parity. The full range of low-lying collective states can then be described by the microscopically based intrinsic $U(6)$ structure, renormalized by coupling to the giant resonance vibrations.
Mirian Tsulaia - One of the best experts on this subject based on the ideXlab platform.
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On the tensionless limit of string theory, off-Shell higher spin interaction vertices and BCFW recursion relations
Journal of High Energy Physics, 2010Co-Authors: Angelos Fotopoulos, Mirian TsulaiaAbstract:We construct an off-Shell Extension of cubic interaction vertices between massless bosonic Higher Spin fields on a flat background which can be obtained from perturbative bosonic string theory. We demonstrate how to construct higher quartic interaction vertices using a simple particular example. We examine whether BCFW recursion relations for interacting Higher Spin theories are applicable. We argue that for several interesting examples such relations should exist, but consistency of the theories might require that we supplement Higher Spin field theories with extended and possibly non-local objects.
A. A. Tseytlin - One of the best experts on this subject based on the ideXlab platform.
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On four-point interactions in massless higher spin theory in flat space
Journal of High Energy Physics, 2017Co-Authors: R. Roiban, A. A. TseytlinAbstract:We consider a minimal interacting theory of a single tower of spin j = 0, 2, 4,… massless Fronsdal fields in flat space with local Lorentz-covariant cubic interaction vertices. We address the question of constraints on possible quartic interaction vertices imposed by the condition of on-Shell gauge invariance of the tree-level four-point scattering amplitudes involving three spin 0 and one spin j particle. We find that these constraints admit a local solution for quartic 000 j interaction term in the action only for j = 2 and j = 4. We determine the non-local terms in four-vertices required in the j ≥ 6 case and suggest that these non-localities may be interpreted as a result of integrating out a tower of auxiliary ghost-like massless higher spin fields in an extended theory with a local action, up to possible higher-point interactions of the ghost fields. We also consider the conformal off-Shell Extension of the Einstein theory and show that the perturbative expansion of its action is the same as that of the non-local action resulting from integrating out the trace of the graviton field from the Einstein action. Motivated by this example, we conjecture the existence of a similar conformal off-Shell Extension of a massless higher spin theory that may be related to the above extended theory. It may then have the same infinite-dimensional symmetry as the higher-derivative conformal higher spin theory and may thus lead to a trivial S matrix.
S. M. Troshin - One of the best experts on this subject based on the ideXlab platform.
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Mass dependence in vector--meson electroproduction
arXiv: High Energy Physics - Phenomenology, 2002Co-Authors: M. A. Perfilov, S. M. TroshinAbstract:We demonstrate that the explicit mass dependence of the exponent in the power--like energy behavior of the vector--meson production cross-section in the processes of virtual photon interactions with a proton gamma^*p --> Vp obtained in the off--Shell Extension of the approach based on unitarity is in a quantitative agreement with the high--energy HERA experimental data.
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Off-Shell unitarity and geometrical effects in deep-inelastic scattering and vector-meson electroproduction
arXiv: High Energy Physics - Phenomenology, 2001Co-Authors: S. M. Troshin, N. E. TyurinAbstract:Deep-inelastic scattering at low x and elastic vector meson production are considered on the basis of the off-Shell Extension of the s-channel unitarity. We discuss behavior of the structure function F_2(x,Q^2) at low x and the total cross-section of virtual photon-proton scattering and obtain, in particular, the dependence sigma^{tot}_{gamma^* p}\sim (W^2)^{lambda(Q^2)} where exponent lambda(Q^2) is related to the interaction radius of a constituent quark. The energy dependence of the total cross-section of gamma^*gamma^*-interactions is calculated. The explicit mass dependence of the exponent in the power energy behavior of the vector meson production in the processes of virtual photon interactions with a proton gamma^*p to Vp has been obtained. We also consider angular distributions at large momentum transfers.
Angelos Fotopoulos - One of the best experts on this subject based on the ideXlab platform.
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On the tensionless limit of string theory, off-Shell higher spin interaction vertices and BCFW recursion relations
Journal of High Energy Physics, 2010Co-Authors: Angelos Fotopoulos, Mirian TsulaiaAbstract:We construct an off-Shell Extension of cubic interaction vertices between massless bosonic Higher Spin fields on a flat background which can be obtained from perturbative bosonic string theory. We demonstrate how to construct higher quartic interaction vertices using a simple particular example. We examine whether BCFW recursion relations for interacting Higher Spin theories are applicable. We argue that for several interesting examples such relations should exist, but consistency of the theories might require that we supplement Higher Spin field theories with extended and possibly non-local objects.