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R R Metsaev - One of the best experts on this subject based on the ideXlab platform.
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Light Cone superstring in ads space time
Nuclear Physics, 2001Co-Authors: R R Metsaev, Charles B Thorn, Arkady A TseytlinAbstract:We consider fixing the bosonic Light-Cone gauge for string in AdS space in the phase space framework, i.e., by choosing x+=τ, and by choosing σ so that P+ is distributed uniformly (its density P+ is independent of σ). We discuss classical bosonic string in AdSd and superstring in AdS5×S5. In the latter case the starting point is the action found in hep-th/0007036, where the κ-symmetry is fixed by a fermionic Light-Cone type gauge. We derive the Light-Cone Hamiltonian in the AdS5×S5 case and in the case of superstring in AdS3×S3. We also obtain a realization of the generators of the basic superalgebra psu(2,2|4) in terms of AdS5×S5 superstring coordinate 2-d fields in the Light-Cone gauge.
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superstring action in ads 5 x s 5 kappa symmetry Light Cone gauge
Physical Review D, 2001Co-Authors: R R Metsaev, Arkady A TseytlinAbstract:As part of program to quantize superstrings in AdS_5 x S^5 background in Light Cone approach we find the explicit form of the corresponding Green-Schwarz action in fermionic Light-Cone kappa-symmetry gauge. The resulting action is quadratic and quartic in fermions. In the flat space limit it reduces to the standard Light-Cone Green-Schwarz action, and also has the correct superparticle limit. We discuss fixing the bosonic Light-Cone gauge and a reformulation of the action in terms of 2-d Dirac spinors.
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Light Cone superstring in ads space time
arXiv: High Energy Physics - Theory, 2000Co-Authors: R R Metsaev, Charles B Thorn, Arkady A TseytlinAbstract:We consider fixing the bosonic Light-Cone gauge for string in AdS in the phase space framework, i.e. by choosing $x^+ = \tau$, and by choosing $\sigma$ so that $P^+$ is distributed uniformly (its density is independent of $\sigma$). We discuss classical bosonic string in AdS space and superstring in AdS_5 x S^5. In the latter case the starting point is the action found in hep-th/0007036 where the kappa-symmetry is fixed by a fermionic Light Cone gauge. We derive the Light Cone Hamiltonian in the AdS_5 x S^5 case and in the case of superstring in AdS_3 x S^3. We also obtain a realization of the generators of the basic symmetry superalgebra psu(2,2|4) in terms of the AdS_5 x S^5 superstring coordinate fields.
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Light Cone form of field dynamics in anti de sitter space time and ads cft correspondence
Nuclear Physics, 1999Co-Authors: R R MetsaevAbstract:Abstract The Light-Cone form of field dynamics in anti-de Sitter space-time is developed. Using field theoretic and group theoretic approaches the Light-Cone representation for generators of the anti-de Sitter algebra acting as differential operators on bulk fields is found. We also present a Light-Cone reformulation of the boundary conformal field theory representations. Making use of these explicit representations of the AdS algebra as an isometry algebra in the bulk and the algebra of conformal transformations at the boundary a precise correspondence between the bulk fields and the boundary operators is established.
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Light Cone form of field dynamics in anti de sitter space time and ads cft correspondence
arXiv: High Energy Physics - Theory, 1999Co-Authors: R R MetsaevAbstract:Light-Cone form of field dynamics in anti-de Sitter space-time is developed. Using field theoretic and group theoretic approaches the Light-Cone representation for generators of anti-de Sitter algebra acting as differential operators on bulk fields is found. We also present Light-Cone reformulation of the boundary conformal field theory representations. Making use of these explicit representations of AdS algebra as isometry algebra in the bulk and the algebra of conformal transformations at the boundary a precise correspondence between the bulk fields and the boundary operators is established.
Risto Paatelainen - One of the best experts on this subject based on the ideXlab platform.
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one loop corrections to Light Cone wave functions the dipole picture dis cross section
Annals of Physics, 2018Co-Authors: H Hanninen, T Lappi, Risto PaatelainenAbstract:Abstract We develop methods to perform loop calculations in Light Cone perturbation theory using a helicity basis, refining the method introduced in our earlier work. In particular this includes implementing a consistent way to contract the four-dimensional tensor structures from the helicity vectors with d -dimensional tensors arising from loop integrals, in a way that can be fully automatized. We demonstrate this explicitly by calculating the one-loop correction to the virtual photon to quark–antiquark dipole Light Cone wave function. This allows us to calculate the deep inelastic scattering cross section in the dipole formalism to next-to-leading order accuracy. Our results, obtained using the four dimensional helicity scheme, agree with the recent calculation by Beuf using conventional dimensional regularization, confirming the regularization scheme independence of this cross section.
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one loop corrections to Light Cone wave functions the dipole picture dis cross section
arXiv: High Energy Physics - Phenomenology, 2017Co-Authors: H Hanninen, T Lappi, Risto PaatelainenAbstract:We develop methods needed to perform loop calculations in Light Cone perturbation theory using a helicity basis, refining the method introduced in our earlier work. In particular this includes implementing a consistent way to contract the four-dimensional tensor structures from the helicity vectors with d-dimensional tensors arising from loop integrals, in a way that can be fully automatized. We demonstrate this explicitly by calculating the one-loop correction to the virtual photon to quark-antiquark dipole Light Cone wave function. This allows us to calculate the deep inelastic scattering cross section in the dipole formalism to next-to-leading order accuracy. Our results, obtained using the four dimensional helicity scheme, agree with the recent calculation by Beuf using conventional dimensional regularization, confirming the regularization scheme independence of this cross section.
Abraham Loeb - One of the best experts on this subject based on the ideXlab platform.
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reionization on large scales iv predictions for the 21 cm signal incorporating the Light Cone effect
The Astrophysical Journal, 2014Co-Authors: P La Plante, N Battaglia, Aravind Natarajan, J B Peterson, Hy Trac, Abraham LoebAbstract:We present predictions for the 21 cm brightness temperature power spectrum during the Epoch of Reionization (EoR). We discuss the implications of the 'Light Cone' effect, which incorporates evolution of the neutral hydrogen fraction and 21 cm brightness temperature along the line of sight. Using a novel method calibrated against radiation-hydrodynamic simulations, we model the neutral hydrogen density field and 21 cm signal in large volumes (L = 2 Gpc h {sup –1}). The inclusion of the Light Cone effect leads to a relative decrease of about 50% in the 21 cm power spectrum on all scales. We also find that the effect is more prominent at the midpoint of reionization and later. The Light Cone effect can also introduce an anisotropy along the line of sight. By decomposing the 3D power spectrum into components perpendicular to and along the line of sight, we find that in our fiducial reionization model, there is no significant anisotropy. However, parallel modes can contribute up to 40% more power for shorter reionization scenarios. The scales on which the Light Cone effect is relevant are comparable to scales where one measures the baryon acoustic oscillation. We argue that due to its large comoving scalemore » and introduction of anisotropy, the Light Cone effect is important when considering redshift space distortions and future application to the Alcock-Paczynski test for the determination of cosmological parameters.« less
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reionization on large scales iv predictions for the 21 cm signal incorporating the Light Cone effect
The Astrophysical Journal, 2014Co-Authors: P La Plante, N Battaglia, Aravind Natarajan, J B Peterson, Hy Trac, Renyue Cen, Abraham LoebAbstract:We present predictions for the 21 cm brightness temperature power spectrum during the Epoch of Reionization (EoR). We discuss the implications of the "Light Cone" effect, which incorporates evolution of the neutral hydrogen fraction and 21 cm brightness temperature along the line of sight. Using a novel method calibrated against radiation-hydrodynamic simulations, we model the neutral hydrogen density field and 21 cm signal in large volumes (L = 2 Gpc h –1). The inclusion of the Light Cone effect leads to a relative decrease of about 50% in the 21 cm power spectrum on all scales. We also find that the effect is more prominent at the midpoint of reionization and later. The Light Cone effect can also introduce an anisotropy along the line of sight. By decomposing the 3D power spectrum into components perpendicular to and along the line of sight, we find that in our fiducial reionization model, there is no significant anisotropy. However, parallel modes can contribute up to 40% more power for shorter reionization scenarios. The scales on which the Light Cone effect is relevant are comparable to scales where one measures the baryon acoustic oscillation. We argue that due to its large comoving scale and introduction of anisotropy, the Light Cone effect is important when considering redshift space distortions and future application to the Alcock-Paczynski test for the determination of cosmological parameters.
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Light Cone distortion of the clustering and abundance of massive galaxies at high redshifts
Monthly Notices of the Royal Astronomical Society, 2008Co-Authors: Joseph A Munoz, Abraham LoebAbstract:Observational surveys of galaxies are not trivially related to single-epoch snapshots from computer simulations. Observationally, an increase in the distance along the line of sight corresponds to an earlier cosmic time at which the properties of the surveyed galaxy population may change. The effect of observing a survey volume along the Light Cone must be considered in the regime where the mass function of galaxies varies exponentially with redshift. This occurs when the haloes under consideration are rare, that is either when they are very massive or observed at high redshift. While the effect of the Light Cone is negligible for narrow-band surveys of Lyα emitters, it can be significant for dropout surveys of Lyman-break galaxies (LBGs) where the selection functions of the photometric bands are broad. Since there are exponentially more haloes at the low-redshift end of the survey, the low-redshift tail of the selection function contains a disproportionate fraction of the galaxies observed in the survey. This leads to a redshift probability distribution for the dropout LBGs with a mean less than that of the photometric selection function (PHSF) by an amount of order the standard deviation of the PHSF. The inferred mass function of galaxies is then shallower than the true mass function at a single redshift with the abundance at the high-mass end being twice or more as large as expected. Moreover, the statistical moments of the count of galaxies calculated ignoring the Light-Cone effect deviate from the actual values.
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Light Cone distortion of the clustering and abundance of massive galaxies at high redshifts
arXiv: Astrophysics, 2007Co-Authors: Joseph A Munoz, Abraham LoebAbstract:Observational surveys of galaxies are not trivially related to single-epoch snapshots from computer simulations. Observationally, an increase in the distance along the line-of-sight corresponds to an earlier cosmic time at which the properties of the surveyed galaxy population may change. The effect of observing a survey volume along the Light-Cone must be considered in the regime where the mass function of galaxies varies exponentially with redshift. This occurs when the halos under consideration are rare, that is either when they are very massive or observed at high-redshift. While the effect of the Light-Cone is negligible for narrow-band surveys of Lyman-alpha emitters, it can be significant for drop-out surveys of Lyman-break galaxies (LBGs) where the selection functions of the photometric bands are broad. Since there are exponentially more halos at the low-redshift end of the survey, the low-redshift tail of the selection function contains a disproportionate fraction of the galaxies observed in the survey. This leads to a redshift probability distribution (RPD) for the dropout LBGs with a mean less than that of the photometric selection function (PHSF) by an amount of order the standard deviation of the PHSF. The inferred mass function of galaxies is then shallower than the true mass function at a single redshift with the abundance at the high-mass end being twice or more as large as expected. Moreover, the statistical moments of the count of galaxies calculated ignoring the Light-Cone effect, deviate from the actual values.
Alexander Khodjamirian - One of the best experts on this subject based on the ideXlab platform.
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pion Light Cone distribution amplitude from the pion electromagnetic form factor
Physical Review D, 2020Co-Authors: Shan Cheng, Alexander Khodjamirian, Aleksey V RusovAbstract:We suggest to probe the pion Light-Cone distribution amplitude, applying a dispersion relation for the pion electromagnetic form factor. Instead of the standard dispersion relation, we use the equation between the spacelike form factor ${F}_{\ensuremath{\pi}}({Q}^{2})$ and the integrated modulus of the timelike form factor. For ${F}_{\ensuremath{\pi}}({Q}^{2})$, the QCD Light-Cone sum rule with a dominant twist-2 term is used. Adopting for the pion twist-2 distribution amplitude a certain combination of the first few Gegenbauer polynomials, it is possible to fit their coefficients ${a}_{2,4,6,..}$. (Gegenbauer moments) from this equation, employing the measured pion timelike form factor. For the exploratory fit we use the data of the BABAR collaboration. The results definitely exclude the asymptotic twist-2 distribution amplitude. Also the model with a single ${a}_{2}\ensuremath{\ne}0$ is disfavored by the fit. Considering the models with ${a}_{ng2}\ensuremath{\ne}0$, we find that the fitted values of the second and fourth Gegenbauer moments cover the intervals ${a}_{2}(1\text{ }\text{ }\mathrm{GeV})=(0.22--0.33)$, ${a}_{4}(1\text{ }\text{ }\mathrm{GeV})=(0.12--0.25)$. The higher moments starting from ${a}_{8}$ are consistent with zero, albeit with large uncertainties. The spacelike pion form factor obtained in two different ways, from the dispersion relation and from the Light-Cone sum rule, agrees, within uncertainties, with the measurement by the Jefferson Lab ${F}_{\ensuremath{\pi}}$ collaboration.
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form factors and strong couplings of heavy baryons from qcd Light Cone sum rules
Journal of High Energy Physics, 2011Co-Authors: Alexander Khodjamirian, Th Mannel, Ch Klein, Y M WangAbstract:We derive QCD Light-Cone sum rules for the hadronic matrix elements of the heavy baryon transitions to nucleon. In the correlation functions the Λ c , Σ c and Λ b -baryons are interpolated by three-quark currents and the nucleon distribution amplitudes are used. To eliminate the contributions of negative parity heavy baryons, we combine the sum rules obtained from different kinematical structures. The results are then less sensitive to the choice of the interpolating current. We predict the Λ b → p form factor and calculate the widths of the Λ b → plν l and Λ b → pπ decays. Furthermore, we consider double dispersion relations for the same correlation functions and derive the Light-Cone sum rules for the Λ c ND (∗) and Σ c ND (∗) strong couplings. Their predicted values can be used in the models of charm production in \( p\bar{p} \) collisions.
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form factors and strong couplings of heavy baryons from qcd Light Cone sum rules
arXiv: High Energy Physics - Phenomenology, 2011Co-Authors: Alexander Khodjamirian, Th Mannel, Ch Klein, Y M WangAbstract:We derive QCD Light-Cone sum rules for the hadronic matrix elements of the heavy baryon transitions to nucleon. In the correlation functions the $\Lambda_c,\Sigma_c$ and $\Lambda_b$ -baryons are interpolated by three-quark currents and the nucleon distribution amplitudes are used. To eliminate the contributions of negative parity heavy baryons, we combine the sum rules obtained from different kinematical structures. The results are then less sensitive to the choice of the interpolating current. We predict the $\Lambda_{b}\to p$ form factor and calculate the widths of the $\Lambda_{b}\to p\ell\nu_l$ and $\Lambda_{b}\to p \pi$ decays. Furthermore, we consider double dispersion relations for the same correlation functions and derive the Light-Cone sum rules for the $\Lambda_cND^{(*)}$ and $\Sigma_cND^{(*)}$ strong couplings. Their predicted values can be used in the models of charm production in $p\bar{p}$ collisions.
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Light Cone sum rules for b pi form factors revisited
Journal of High Energy Physics, 2008Co-Authors: G Duplancic, Alexander Khodjamirian, Th Mannel, Blaženka Melic, Nils OffenAbstract:We reconsider and update the QCD Light-Cone sum rules for B → π form factors. The gluon radiative corrections to the twist-2 and twist-3 terms in the correlation functions are calculated. The b-quark mass is employed, instead of the one-loop pole mass used in the previous analyses. The Light-Cone sum rule for f+Bπ(q2) is fitted to the measured q2-distribution in B → πlνl, fixing the input parameters with the largest uncertainty: the Gegenbauer moments of the pion distribution amplitude. For the B → π vector form factor at zero momentum transfer we predict f+Bπ(0) = 0.26+0.04−0.03. Combining it with the value of the product |Vubf+Bπ(0)| extracted from experiment, we obtain |Vub| = (3.5±0.4±0.2±0.1) × 10−3. In addition, the scalar and penguin B → π form factors f0Bπ(q2) and fTBπ(q2) are calculated.
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form factors from Light Cone sum rules with b meson distribution amplitudes
Physical Review D, 2007Co-Authors: Alexander Khodjamirian, Thomas Mannel, Nils OffenAbstract:New sum rules for B{yields}{pi},K and B{yields}{rho},K* form factors are derived from the correlation functions expanded near the Light Cone in terms of B-meson distribution amplitudes. The contributions of quark-antiquark and quark-antiquark-gluon components in the B meson are taken into account. Models for the B-meson three-particle distribution amplitudes are suggested, based on QCD sum rules in heavy-quark effective theory. Employing the new Light-Cone sum rules, we calculate the form factors at small momentum transfers, including SU(3)-violation effects. The results agree with the predictions of the conventional Light-Cone sum rules.
Kweichou Yang - One of the best experts on this subject based on the ideXlab platform.
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form factors ofbu d sdecays intop wave axial vector mesons in the Light Cone sum rule approach
Physical Review D, 2008Co-Authors: Kweichou YangAbstract:We calculate the vector and axial-vector form factors of B{sub u,d,s} decays into P-wave axial-vector mesons in the Light-Cone sum rule approach. For the sum rule results, we have included corrections of order m{sub A}/m{sub b}, where m{sub A} is the mass of the axial-vector meson A. The results are relevant to the Light-Cone distribution amplitudes of the axial-vector mesons. It is important to note that, owing to the G parity, the chiral-even two-parton Light-Cone distribution amplitudes of the {sup 3}P{sub 1} ({sup 1}P{sub 1}) mesons are symmetric (antisymmetric) under the exchange of quark and antiquark momentum fractions in the SU(3) limit. For chiral-odd Light-Cone distribution amplitudes, it is the other way around. The predictions for decay rates of B{sub u,d,s}{yields}Ae{nu}{sub e} are also presented.
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Light Cone distribution amplitudes of axial vector mesons
Nuclear Physics, 2007Co-Authors: Kweichou YangAbstract:Abstract We have presented a detailed study of twist-2 and twist-3 Light-Cone distribution amplitudes of 1 P 1 3 and 1 P 1 1 axial-vector mesons, based on QCD conformal partial wave expansion. Applying equations of motion, the twist-three two-parton Light-Cone distribution amplitudes can be expressed in terms of leading-twist and twist-three three-parton Light-Cone distribution amplitudes. The relevant G-parity invariant and violating parameters, containing the corrections due to the SU ( 3 ) breaking effects, are evaluated from the QCD sum rule method. The results for axial-vector decay constants of 1 P 1 3 states are presented. The values of tensor decay constants and Gegenbauer moments of the leading twist distribution amplitudes for 1 P 1 1 states are updated. Using Gell-Mann–Okubo mass formula, the mixing angle for the f 8 and f 1 of 1 P 1 3 states is θ P 1 3 ∼ 38 ° , and that for h 8 and h 1 of 1 P 1 1 states is θ P 1 1 ∼ 10 ° . The detailed properties for physical states f 1 ( 1285 ) , f 1 ( 1420 ) , h 1 ( 1170 ) , and h 1 ( 1380 ) are given. Assuming the mixing angle between K 1 A and K 1 B to be θ K = 45 ° or −45°, we also give the detailed study for K 1 ( 1270 ) and K 1 ( 1400 ) . Using the conformal partial wave expansion, we obtain the models for Light-Cone distribution amplitudes, containing contributions up to conformal spin 9/2. It is interesting to note that some distribution amplitudes have significant asymmetric behaviors, which should be phenomenologically attractive.