Jiang, H. C., Krüger, F., Moore, J. E., Sheng, D. N., Zaanen, J., Weng, Z. Y.
We study the S=1 square lattice Heisenberg antiferromagnet with spatially anisotropic nearest neighbor couplings $J_{1x}$, $J_{1y}$ frustrated by a next-nearest neighbor coupling $J_{2}$ numerically...
Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors (2008)
Krüger, F., Kumar, S., Zaanen, J., Brink, J. Van Den
We develop an understanding of the anomalous metal state of the parent compounds of recently discovered iron based superconductors starting from a strong coupling viewpoint, including orbital degrees...
Pacifying the Fermi-liquid: battling the devious fermion signs (2008)
Zaanen, J., Krüger, F., Sadri, D., Mukhin, S. I.
The fermion sign problem is studied in the path integral formalism. The standard picture of Fermi liquids is first critically analyzed, pointing out some of its rather peculiar properties. The...
Magnetic fluctuations in n-type high-$T_c$ superconductors reveal breakdown of fermiology (2007)
Krüger, F., Wilson, S. D., Shan, L., Li, S., Huang, Y., ...
By combining experimental measurements of the quasiparticle and dynamical magnetic properties of optimally electron-doped Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$ with theoretical calculations we demonstrate...
Influence of the seismic noise characteristics on noise correlations in the Baltic shield (2007)
Pedersen, Helle A., Krüger, F.
It has recently been shown that correlations of seismic noise can contain significant information about the Green's function along the station profile. Using an array of 38 temporary broad-band...
Influence of the seismic noise characteristics on noise correlations in the Baltic shield (2007)
Pedersen, Helle A., Krüger, F.
It has recently been shown that correlations of seismic noise can contain significant information about the Green's function along the station profile. Using an array of 38 temporary broad-band...
Seismic array analysis of Tornillo-like signals recorded in Tuscany (2006)
Braun, T.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma1, Roma, Italia, Dahm, T.; Inst. F. Geophysik, Uni Hamburg, Krüger, F.; Inst. F. Geowissenschaften, Uni Potsdam, Ohrnberger, M.; Inst. F. Geowissenschaften, Uni Potsdam, Scherbaum, F.; Inst. F. Geowissenschaften, Uni Potsdam
With the scientific purpose to monitor the micro-seismicity in the Central Apennines, we recently deployed in Eastern Tuscany (Casentino) a temporary 12 element seismic array, composed exclusively of...
Spin wave dispersion in orbitally ordered La1/2Sr3/2MnO4 (2006)
Senff, D, Krüger, F, Scheidl, S, Benomar, M, Sidis, Y, Demmel, F, ...
More Model-Independent Analysis of b->s Processes (2003)
We study model-independently the implications of non-standard scalar and pseudoscalar interactions for the decays b ->s gamma, b -> s g, b -> s l^+l^- (l=e,mu) and B_s -> mu^+ mu^-. We find sizeable...
Bobeth, C., Ewerth, T., Krüger, F., Urban, J.
We extend our previous analysis of the decays B_{d,s} -> mu^+ mu^- in the Minimal Supersymmetric Standard Model (MSSM) to include gluino and neutralino contributions. We provide analytic formulae,...
Bobeth, C., Buras, A. J., Krüger, F., Urban, J.
We compute for the first time QCD corrections to the rare decays B -> X_{d,s} nu nubar, B_{d,s} -> l^+ l^-, K -> pi nu nubar and K_L -> mu^+ mu^-, where l=e or mu, in the context of a supersymmetric...
Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard Model (2001)
Branco, Gustavo Castello, Krüger, F, Romão, J C, Teixeira, A M
We re-examine spontaneous $\cp$ violation (SCPV) at the tree level in the context of the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs doublets and a gauge singlet field. We...
Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard Model (2001)
Branco, G. C., Krüger, F., Romão, J. C., Teixeira, A. M.
We re-examine spontaneous $\cp$ violation (SCPV) at the tree level in the context of the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs doublets and a gauge singlet field. We...
Analysis of Neutral Higgs-Boson Contributions to the Decays B_s -> l^+l^- and B -> K l^+l^- (2001)
Bobeth, C., Ewerth, T., Krüger, F., Urban, J.
We report on a calculation of Higgs-boson contributions to the decays B_s -> l^+l^- and B -> K l^+l^- (l=e, mu) which are governed by the effective Hamiltonian describing b -> s l^+ l^-. Compact...
Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard Model Revisited (2000)
Branco, Gustavo Castello, Krüger, F, Romão, J C, Teixeira, A F F
We re-examine spontaneous CP violation at the tree level in the context of the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs doublets H_{1,2} and a gauge singlet field N....
Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard Model Revisited (2000)
Branco, G. C., Krüger, F., Romão, J. C., Teixeira, A. M.
We re-examine spontaneous CP violation at the tree level in the context of the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs doublets and a gauge singlet field. We analyse the...
Looking for Novel CP-Violating Effects in B->K^*l^+l^- (2000)
The CP-violating asymmetries in the exclusive decay B->K^*l^+l^- (l=e,mu,tau) are predicted to be exceedingly small in the standard model (SM), thereby offering an opportunity to assess various...
Flavour-Conserving CP Phases in Supersymmetry and Implications for Exclusive B Decays (2000)
We study rare exclusive B decays based on the quark-level transition b->s(d)l^+l^-, where l=e or mu, in the context of supersymmetric theories with minimal flavour violation. We present analytic...
Angular Distribution and CP Asymmetries in the Decays B->K^-pi^+e^-e^+ and B->pi^-pi^+e^-e^+ (1999)
Krüger, F., Sehgal, L. M., Sinha, N., Sinha, R.
The short-distance Hamiltonian describing b->s(d)e^-e^+ in the standard model is used to obtain the decay spectrum of \bar{B}->K^-pi^+e^-e^+ and \bar{B}->pi^-pi^+e^-e^+, assuming the Kpi and pipi...
A Real CKM Matrix and Physics Beyond the Standard Model (1999)
Branco, G. C., Cagarrinho, F., Krüger, F.
We study the possible existence of a real Cabibbo-Kobayashi-Maskawa (CKM) matrix, with CP violation originating from physics beyond the standard model (SM). We show that present experimental data...
CP Violation in Selected B Decays (1997)
We summarize the results of two papers in which we have studied CP violation in inclusive and exclusive decays b -> d e^+e^-. Two CP-violating effects are calculated: the partial rate asymmetry...
CP Violation in the Exclusive Decays B -> pi e^+e^- and B -> rho e^+e^- (1997)
As a sequel to the calculation of the CP-violating asymmetry in the decay rates of b -> d l^+l^- and \bar{b} -> \bar{d} l^+l^-, we address in this paper the asymmetry in exclusive channels \bar{B} ->...
CP Violation in the Decay B \to X_d e^+ e^- (1996)
The decay $b\to d e^+e^-$ has an amplitude containing comparable contributions proportional to $V_{tb}V_{td}^{*}$, $V_{cb}V_{cd}^{*}$ and $V_{ub}V_{ud}^{*}$. These pieces involve different unitarity...
Lepton Polarization in the Decays $B\to X_s\mu^+\mu^-$ and $B\to X_s\tau^+\tau^-$ (1996)
The effective Hamiltonian for the decay $b\to s l^+ l^-$ predicts a characteristic polarization for the final state lepton, which can serve as an important test of the underlying theory. The lepton...
Gremm, M., Köpp, G., Krüger, F., Sehgal, L. M.
We consider the effects of quark-binding on the angular distribution and polarization characteristics of the inclusive decays $\Lambda_b \to X_s \gamma$ and $\Lambda_b \to X_c l \bar{\n}_l$ $(l=e,...
Gremm, M., Krüger, F., Sehgal, L. M.
We study the angular distribution of photons produced in the inclusive decay of a polarized $\Lambda_b$, $\Lambda_b\to X_s\,\gamma$, using the technique of Heavy Quark Effective Theory. Finite...