The El Gordo galaxy cluster challenges {\Lambda}CDM for any plausible collision velocity

El Gordo (ACT-CL J0102-4915) is an extraordinarily large and bright galaxy cluster collision. In a previous study, we found that El Gordo is in $6.2\sigma$ tension with the $\Lambda$CDM standard model when assuming the nominal mass and infall velocity values from the hydrodynamical simulations of Zhang et al. ($M_{200} = 3.2 \times 10^{15} M_{\odot}$ and $V_{\textrm{infall}} = 2500~\textrm{km~s}^{-1}$, respectively). The recent weak lensing study of Kim et al. showed that the mass of El Gordo is actually $2.13^{+0.25}_{-0.23} \times 10^{15} M_{\odot}$. Here we explore the level of tension between El Gordo and $\Lambda$CDM for the new mass estimate, assuming several $V_{\textrm{infall}}$ values. We find that in order to reduce the tension below the $5\sigma$ level, the El Gordo subclusters should have $V_{\textrm{infall}} < 2300~\textrm{km~s}^{-1}$ ($V_{\textrm{infall}} < 1800~\textrm{km~s}^{-1}$ when considering the combined tension with the Bullet Cluster). To the best of our knowledge, the El Gordo hydrodynamical simulations conducted so far require $V_{\textrm{infall}} \geq 2500~\textrm{km~s}^{-1}$ to simultaneously reproduce its morphology and its high X-ray luminosity and temperature. We therefore conclude that El Gordo still poses a significant challenge to $\Lambda$CDM cosmology. Whether the properties of El Gordo can be reconciled with a lower $V_{\textrm{infall}}$ should be tested with new hydrodynamical simulations that explore different configurations of the interaction.Comment: 8 pages, 1 figure. Accepted for publication in The Astrophysical Journal in this for

Observation and analysis of Fano-like lineshapes in the Raman spectra of molecules adsorbed at metal interfaces

Surface enhanced Raman spectra from molecules (bipyridyl ethylene) adsorbed on gold dumbells are observed to become increasingly asymmetric (Fano-like) at higher incident light intensity. The electronic temperature (inferred from the anti-Stokes (AS) electronic Raman signal increases at the same time while no vibrational AS scattering is seen. These observations are analyzed by assuming that the molecule-metal coupling contains an intensity dependent contribution (resulting from light-induced charge transfer transitions as well as renormalization of the molecule metal tunneling barrier). We find that interference between vibrational and electronic inelastic scattering routes is possible in the presence of strong enough electron-vibrational coupling and can in principle lead to the observed Fano-like feature in the Raman scattering profile. However the best fit to the observed results, including the dependence on incident light intensity and the associated thermal response is obtained from a model that disregards this coupling and accounts for the structure of the continuous electronic component of the Raman scattering signal. The temperatures inferred from the Raman signal are argued to be only of qualitative value.Comment: 20 pages, 12 figure

Degree of Complementarity Determines the Nonlocality in Quantum Mechanics

Complementarity principle is one of the central concepts in quantum mechanics which restricts joint measurement for certain observables. Of course, later development shows that joint measurement could be possible for such observables with the introduction of a certain degree of unsharpness or fuzziness in the measurement. In this paper, we show that the optimal degree of unsharpness, which guarantees the joint measurement of all possible pairs of dichotomic observables, determines the degree of nonlocality in quantum mechanics as well as in more general no-signaling theories.Comment: Close to published versio

Exotic phases in compact stars

We discuss how the co-existence of hyperons, antikaon condensate and color superconducting quark matter in neutron star interior influences the gross properties of compact stars such as, the equation of state and mass-radius relationship. We compare our results with the recent observations. We also discuss about superdense stars in the third family branch which may contain a pure color-flavor-locked (CFL) core.Comment: 6 pages, presented in "Strange Quarks in Matter" (SQM2003) conference, Atlantic Beach, NC, USA, March 12-17, 2003 and to be published in J. Phys.

Strange matter in rotating compact stars

We have constructed equations of state involving various exotic forms of matter with large strangeness fraction such as hyperon matter, Bose-Einstein condensates of antikaons and strange quark matter. First order phase transitions from hadronic to antikaon condensed and quark matter are considered here. The hadronic phase is described by the relativistic field theoretical model. Later those equations of state are exploited to investigate models of uniformly rotating compact stars. The effect of rotation on the third family branch for the equation of state involving only antikaon condensates is investigated. We also discuss the back bending phenomenon due to a first order phase transition from $K^-$ condensed to quark matter.Comment: 8 pages, 4 figures; Plenary talk delivered at Strangeness in Quark Matter (SQM) 2004 held in Cape Town, South Africa from 15-20 September; Accepted for publication in the proceedings in Journal of Physics

Kaons production at finite temperature and baryon density in an effective relativistic mean field model

We investigate the kaons production at finite temperature and baryon density by means of an effective relativistic mean-field model with the inclusion of the full octet of baryons. Kaons are considered taking into account of an effective chemical potential depending on the self-consistent interaction between baryons. The obtained results are compared with a minimal coupling scheme, calculated for different values of the anti-kaon optical potential.Comment: 3 pages, contribution presented to the International Conference on Exotic Atoms and Related Topic

Density dependent hadron field theory for neutron stars with antikaon condensates

We investigate $K^-$ and $\bar K^0$ condensation in $\beta$-equilibrated hyperonic matter within a density dependent hadron field theoretical model. In this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. Density dependent meson-baryon coupling constants are obtained from microscopic Dirac Brueckner calculations using Groningen and Bonn A nucleon-nucleon potential. It is found that the threshold of antikaon condensation is not only sensitive to the equation of state but also to antikaon optical potential depth. Only for large values of antikaon optical potential depth, $K^-$ condensation sets in even in the presence of negatively charged hyperons. The threshold of $\bar K^0$ condensation is always reached after $K^-$ condensation. Antikaon condensation makes the equation of state softer thus resulting in smaller maximum mass stars compared with the case without any condensate.Comment: 20 pages, 7 figures; final version to appear in Physical Review