Maximal supersymmetry and exceptional groups

The article is a tribute to my old mentor, collaborator and friend Murray Gell-Mann. In it I describe work by Pierre Ramond, Sung-Soo Kim and myself where we describe the N = 8 Supergravity in the light-cone formalism. We show how the Cremmer-Julia E7(7) non-linear symmetry is implemented and how the full supermultiplet is a representation of the E7(7) symmetry. I also show how the E7(7) symmetry is a key to understand the higher order couplings in the theory and is very useful when we discuss possible counterterms for this theory.Comment: Proceedings of Conference in Honour of Murray Gell-Mann's 80th Birthda

On the eikonal approach to nuclear diffraction dissociation

The study of nuclear breakup of halo and weakly bound particles has been one of the key ingredients in the understanding of exotic nuclei during the last thirty years. One of the most used methods to analyse data, in particular absolute breakup cross sections, has been the eikonal approximation. Here we revise critically the formalisms used for calculating the diffraction dissociation part of nuclear breakup and show that there is a formula that can be applied to breakup on any target, while a most commonly used formula must be restricted to light targets as it contains also the effect of Coulomb breakup calculated to first order in the sudden approximation which is well known for not being accurate.Comment: 5 pages, 1 figur

How massless are massless fields in AdSdAdS_d

Massless fields of generic Young symmetry type in $AdS_d$ space are analyzed. It is demonstrated that in contrast to massless fields in Minkowski space whose physical degrees of freedom transform in irreps of $o(d-2)$ algebra, $AdS$ massless mixed symmetry fields reduce to a number of irreps of $o(d-2)$ algebra. From the field theory perspective this means that not every massless field in flat space admits a deformation to $AdS_d$ with the same number of degrees of freedom, because it is impossible to keep all of the flat space gauge symmetries unbroken in the AdS space. An equivalent statement is that, generic irreducible AdS massless fields reduce to certain reducible sets of massless fields in the flat limit. A conjecture on the general pattern of the flat space limit of a general $AdS_d$ massless field is made. The example of the three-cell ``hook'' Young diagram is discussed in detail. In particular, it is shown that only a combination of the three-cell flat-space field with a graviton-like field admits a smooth deformation to $AdS_d$.Comment: 23 pages, LaTeX, a few typos correcte

Determining the Electron-Phonon Coupling Strength in Correlated Electron Systems from Resonant Inelastic X-ray Scattering

We show that high resolution Resonant Inelastic X-ray Scattering (RIXS) provides direct, element-specific and momentum-resolved information on the electron-phonon (e-p) coupling strength. Our theoretical analysis demonstrates that the e-p coupling can be extracted from RIXS spectra by determining the differential phonon scattering cross section. An alternative, very direct manner to extract the coupling is to use the one and two-phonon loss ratio, which is governed by the e-p coupling strength and the core-hole life-time. This allows measurement of the e-p coupling on an absolute energy scale.Comment: 4 pages, 3 figure

A relativistic treatment of pion wave functions in the annihilation antiproton-proton -> pi^-pi^+

Quark model intrinsic wave functions of highly energetic pions in the reaction \bar pp->\pi^-\pi^+ are subjected to a relativistic treatment. The annihilation is described in a constituent quark model with A2 and R2 flavor-flux topology and the annihilated quark-antiquark pairs are in 3P_0 and 3S_1 states. We study the effects of pure Lorentz transformations on the antiquark and quark spatial wave functions and their respective spinors in the pion. The modified quark geometry of the pion has considerable impact on the angular dependence of the annihilation mechanisms.Comment: 10 pages in revtex format, 3 figure

Three-body model calculations for 16C nucleus

We apply a three-body model consisting of two valence neutrons and the core nucleus $^{14}$C in order to investigate the ground state properties and the electronic quadrupole transition of the $^{16}$C nucleus. The discretized continuum spectrum within a large box is taken into account by using a single-particle basis obtained from a Woods-Saxon potential. The calculated B(E2) value from the first 2$^+$ state to the ground state shows good agreement with the observed data with the core polarization charge which reproduces the experimental B(E2) value for $^{15}$C. We also show that the present calculation well accounts for the longitudinal momentum distribution of $^{15}$C fragment from the breakup of $^{16}$C nucleus. We point out that the dominant ($d_{5/2})^2$ configuration in the ground state of $^{16}$C plays a crucial role for these agreement.Comment: 5 pages, 3 figures, 3 table

Supertraces on the algebra of observables of the rational Calogero model based on the classical root system

A complete set of supertraces on the algebras of observables of the rational Calogero models with harmonic interaction based on the classical root systems of B_N, C_N and D_N types is found. These results extend the results known for the case A_N. It is shown that there exist Q independent supertraces where Q(B_N)=Q(C_N) is a number of partitions of N into a sum of positive integers and Q(D_N) is a number of partitions of N into a sum of positive integers with even number of even integers.Comment: 10 pages, LATE