arXiv subjects

Doron Gazit

Publications and source records attributed to Doron Gazit.

34 records · Page 2Linked to original sources

arXiv2009

Correlation between Charge Inhomogeneities and Structure in Graphene and Other Electronic Crystalline Membranes

Only one atom thick and not inclined to lattice defects, graphene represents the ultimate crystalline membrane. However, its structure reveals unique features not found in other crystalline membranes, in particular the existence of ripples with wavelength of 100-300 Angstroms. Here, I trace the origin of this difference to the free electrons in the membrane. The deformation energy of the lattice creates a coupling between charge fluctuations and the structure, resulting in ripples on the membrane, correlated with charge inhomogeneities. In graphene this mechanism reproduces the experimental result for both charge puddles and ripples.

cond-mat.mtrl-sci↗

arXiv2009

The Structure of Physical Crystalline Membranes within the Self-Consistent Screening Approximation

The anomalous exponents governing the long wavelength behavior of the flat phase of physical crystalline membranes are calculated within a self-consistent screening approximation (SCSA) applied to second order expansion in 1/d_C (d_C is the co-dimension), extending the seminal work of Le Doussal and Radzihovsky [Phys. Rev. Lett. 69, 1209 (1992)]. In particular, the bending rigidity is found to harden algebraically in the long wavelength limit with an exponent eta=0.789..., which is used to extract the elasticity softening exponent eta_u=0.422..., and the roughness exponent zeta=0.605.... The scaling relation eta_u=2-2eta is proven to hold to all orders in SCSA. Further, applying the SCSA to an expansion in 1/d_C, is found to be essential, as no solution to the self-consistent equations is found in a two bubble level, which is the naive second order expansion. Surprisingly, even though the expansion parameter for physical membrane is 1/d_C=1, the SCSA applied to second order expansion deviates only slightly from the first order, increasing zeta by mere 0.016. This supports the high quality of the SCSA for physical crystalline membranes, as well as improves the comparison to experiments and numerical simulations of these systems. The prediction of SCSA applied to first order expansion for the Poisson ratio is shown to be exact to all orders.

cond-mat.stat-mech↗

arXiv2009

Three-Nucleon Low-Energy Constants from the Consistency of Interactions and Currents in Chiral Effective Field Theory

The chiral low-energy constants c_D and c_E are constrained by means of accurate ab initio calculations of the A=3 binding energies and, for the first time, of the triton beta decay. We demonstrate that these low-energy observables allow a robust determination of the two undetermined constants. The consistency of the interactions and currents in chiral effective field theory is crucial to this remarkable result. The two- plus three-nucleon interactions from chiral effective field theory defined by properties of the A=2 system and the present determination of c_D and c_E are successful in predicting properties of the A=3, and 4 systems.

nucl-th↗

arXiv2009

6He beta-decay rate and the suppression of the axial constant in nuclear matter

We present a microscopic calculation of the 6He beta-decay into the ground state of 6Li. To this end, we use chiral perturbation theory at next-to-next-to-next-to-leading order to describe the nuclear weak-currents. The nuclear wave functions are derived from the J-matrix inverse scattering nucleon-nucleon potential (JISP), and the Schroedinger equation is solved using the hyperspherical-harmonics expansion. Our calculation brings the theoretical decay-rate within 3% of the measured one. This success is attributed to the use of chiral-perturbation-theory based mesonic currents, whose contribution is qualitatively different compared to standard nuclear physics approach, where the use of meson exchange currents worsens the comparison to experiment. The inherent inconsistency in the use of the JISP potential together with chiral-perturbation-theory based is argued not to affect this conclusion, though a more detailed investigation is called for. We conclude that any suppression of the axial constant in nuclear matter is included in this description of the weak interaction in the nucleus.

nucl-th↗

arXiv2009

Theory of the spontaneous buckling of doped graphene

Graphene is a realization of an esoteric class of materials -- electronic crystalline membranes. We study the interplay between the free electrons and the two-dimensional crystal, and find that it induces a substantial effect on the elastic structure of the membrane. For the hole-doped membrane, in particular, we predict a spontaneous buckling. In addition, attenuation of elastic waves is expected, due to the effect of corrugations on the bulk modulus. These discoveries have a considerable magnitude in graphene, affecting both its mesoscopic structure, and its electrical resistivity, which has an inherent asymmetry between hole- and electron-doped graphene.

cond-mat.mtrl-sci↗

arXiv2009

Weak reactions with light nuclei - 6He beta-decay as a test case for the nuclear weak current

We present a microscopic calculation of the 6He beta-decay into the ground state of 6Li. To this end we use the impulse approximation to describe the nuclear weak current. The ground state wave functions are obtained from the solution of the nuclear 6-body problem. The nucleonnucleon interaction is described via the J-matrix inverse scattering potential (JISP), and the nuclear problem is solved using the hyperspherical-harmonics approach. This approach results in numerical accuracy of about 2 per mil in the transition matrix element. Bearing in mind that the contribution of meson-exchange currents to the transition matrix element is about 5%, these results pave the way for accurate estimation of their effect.

nucl-th↗

arXiv2009

Weak Interaction in Holographic QCD

We present a recent proposal of a simple prescription for including low-energy weak-interactions into the framework of holographic QCD, based on the standard AdS/CFT dictionary of double-trace deformations. This opens a new perspective on phenomenological applications of holographic QCD: calculating weak observables in the strongly coupled regime of QCD. The idea is general enough to be implemented in any holographic model. Its efficiency and usefulness are demonstrated by performing few exemplar calculations of weak reactions involving mesons and baryons, within the Sakai-Sugimoto and hard/soft wall holographic models.

hep-th↗

arXiv2009

The weak structure of the nucleon from muon capture on 3He

I use a microscopic calculation of the weak capture process 3He(μ^{-},ν_μ)3H, to extract and constrain the weak form factors of the nucleon, particularly the induced pseudo-scalar, and the second-class currents. The induced pseudo-scalar form-factor is found to agree with the prediction of chiral perturbation theory. The constraint found on the conservation of vector current (CVC) hypothesis is the tightest to date.

nucl-th↗

arXiv2008

Weak-Interacting Holographic QCD

We propose a simple prescription for including low-energy weak-interactions into the framework of holographic QCD, based on the standard AdS/CFT dictionary of double-trace deformations. As our proposal enables us to calculate various electro-weak observables involving strongly coupled QCD, it opens a new perspective on phenomenological applications of holographic QCD. We illustrate efficiency and usefulness of our method by performing a few exemplar calculations; neutron beta decay, charged pion weak decay, and meson-nucleon parity non-conserving (PNC) couplings. The idea is general enough to be implemented in both Sakai-Sugimoto as well as Hard/Soft Wall models.

hep-th↗

arXiv2008

Electro-Weak Interactions in Light Nuclei

In this thesis, conducted in the field of few--body nuclear physics,I studied low energy inelastic reactions of electro--weak probes on light nuclei. Such interactions hold experimental and theoretical attention in recent years because of the role they play in various fields of physics, stretching from checking the standard model limits; through nuclear structure and dynamics research; up to microscopic interaction in astrophysical phenomena, such as supernova explosion and the nucleosynthesis of the elements. The reactions considered in this work are: (i) Neutrino interaction with A=3 and $^4$He nuclei, in energies typical to core-collapse supernova. For $^4$He both the neutral and charged current reactions were calculated, whereas only neutral current reactions are calculated for A=3 nuclei. (ii) Photoabsorption on $^4$He. This long standing problem has been the attraction of theoretical and experimental efforts in the last three decades. The calculations make use of two novel methods. the Lorentz Integral Transform (LIT) method, which is used to transform the scattering problem to a bound state like problem. The resulting equations are solved using the Effective Interaction in the Hyperspherical Harmonics (EIHH) method.

nucl-th↗

arXiv2008

Muon Capture on 3He and the Weak Structure of the Nucleon

The weak form factors of the nucleon, including the induced pseudoscalar form factor and second class terms, are constrained using a microscopic calculation of the weak capture process $^3He(μ^{-},ν_μ)^3{H}$. The calculation is parameter free, and yields a rate of 1499(16) Hz, in agreement with the remarkable experimental measurement 1496(4) Hz. The nuclear wave functions are obtained using the EIHH method with the Argonne V18 nucleon--nucleon potential and the Urbana-IX three nucleon force. The weak currents in the nuclei are described using HB$χ$PT formalism. The induced pseudoscalar form factor is found to agree with HB$χ$PT prediction. The result is compatible with vanishing second class currents, with the tightest constraint to date on the conservation of vector current (CVC) hypothesis.

nucl-th↗

arXiv2007

Few body Calculation of Neutrino Neutral Inelastic scattering on 4He

The inelastic neutral reaction of neutrino on 4He is calculated using two modern nucleon--nucleon potentials. Full final state interaction among the four nucleons is considered, via the Lorentz integral transform (LIT) method. The effective interaction hyperspherical-harmonic (EIHH) approach is used to solve the resulting Schrodinger like equations. A detailed energy dependent calculation is given in the impulse approximation.

nucl-th↗

arXiv2007

Low-Energy Inelastic Neutrino Reactions on 4He

The inelastic scattering of neutrino off 4He is calculated microscopically at energies typical for core collapse supernova environment. The calculation is carried out with the Argonne V18 nucleon--nucleon potential and the Urbana IX three nucleon force. Full final state interaction is included via the Lorentz integral transform (LIT) method. The contribution of axial meson exchange currents to the cross sections is taken into account from effective field theory of nucleons and pions to order O(Q^3).

nucl-th↗

arXiv2006

Photonuclear sum rules and the tetrahedral configuration of $^4$He

Three well known photonuclear sum rules (SR), i.e. the Thomas-Reiche-Kuhn, the bremsstrahlungs and the polarizability SR are calculated for 4He with the realistic nucleon-nucleon potential Argonne V18 and the three-nucleon force Urbana IX. The relation between these sum rules and the corresponding energy weighted integrals of the cross section is discussed. Two additional equivalences for the bremsstrahlungs SR are given, which connect it to the proton-neutron and neutron-neutron distances. Using them, together with our result for the bremsstrahlungs SR, we find a deviation from the tetrahedral symmetry of the spatial configuration of 4He. The possibility to access this deviation experimentally is discussed.

nucl-th↗

arXiv2004

A microscopic calculation of neutrino neutral reaction on 4He

An ab-initio calculation of the inelastic neutral reaction of neutrino on 4He is presented, including realistic nuclear force and full final state interaction among the four nucleons. The calculation uses the powerful combintation of the Lorentz integral transform (LIT) method and the hyperspherical-harmonic effective interaction approach (EIHH). The neutrino - nucleus interaction is taken in the impulse approximation. With respect to previous calculations, the current work predicts an increased reaction cross-section by 10%-30% for neutrino temperature up to 15 MeV.

nucl-th↗

arXiv2004

Neutrino neutral reaction on 4He, effects of final state interaction and realistic NN force

The inelastic neutral reaction of neutrino on 4He is calculated microscopically, including full final state interaction among the four nucleons. The calculation is performed using the Lorentz integral transform (LIT) method and the hyperspherical-harmonic effective interaction approach (EIHH), with a realistic nucleon-nucleon interaction. A detailed energy dependent calculation is given in the impulse approximation. With respect to previous calculations, this work predicts an increased reaction cross-section by 10%-30% for neutrino temperature up to 15 MeV.

nucl-th↗