On stability of the three-dimensional fixed point in a model with three coupling constants from the ϵ\epsilon expansion: Three-loop results

The structure of the renormalization-group flows in a model with three quartic coupling constants is studied within the $\epsilon$-expansion method up to three-loop order. Twofold degeneracy of the eigenvalue exponents for the three-dimensionally stable fixed point is observed and the possibility for powers in $\sqrt{\epsilon}$ to appear in the series is investigated. Reliability and effectiveness of the $\epsilon$-expansion method for the given model is discussed.Comment: 14 pages, LaTeX, no figures. To be published in Phys. Rev. B, V.57 (1998

Autologous anti-SOX2 antibody responses reflect intensity but not frequency of antigen expression in small cell lung cancer

Background: Anti-SOX2 antibody responses are observed in about 10 to 20% of small cell lung cancer (SCLC) patients. The aim of this study was to determine whether such responses reflect a particular pattern of SOX2 protein expression in the tumor and whether this pattern associates with clinical outcome. Methods. Paraffin embedded tumor tissues, obtained from SCLC patients who had no evidence of paraneoplastic autoimmune degeneration, were evaluated for SOX2 expression by immunohistochemistry for both intensity and extent of staining. Sera from the same patients were tested for autologous antibodies against recombinant SOX2 by enzyme-linked immunosorbent assay (ELISA). Correlates between overall survival and various clinical parameters including SOX2 staining and serology were determined. Results: SOX2 protein expression was observed in tumor tissue in 89% of patients. Seventeen patients (29%) were seropositive for SOX2 antibodies and, in contrast to SOX2 staining, the presence of antibody correlated with limited disease stage (p = 0.05). SOX2 seropositivity showed a significant association with the intensity of SOX2 staining in the tumor (p = 0.02) but not with the frequency of SOX2 expressing cells. Conclusion: Anti-SOX2 antibodies associate with better prognosis (limited stage disease) while SOX2 protein expression does not; similar to reports from some earlier studies. Our data provides an explanation for this seemingly contrasting data for the first time as SOX2 antibodies can be observed in patients whose tumors contain relatively few but strongly staining cells, thus supporting the possible presence of active immune-surveillance and immune-editing targeting SOX2 protein in this tumor type. © 2014 Atakan et al.; licensee BioMed Central Ltd

Autologous anti-SOX2 antibody responses reflect intensity but not frequency of antigen expression in small cell lung cancer

Cataloged from PDF version of article.Background: Anti-SOX2 antibody responses are observed in about 10 to 20% of small cell lung cancer (SCLC) patients. The aim of this study was to determine whether such responses reflect a particular pattern of SOX2 protein expression in the tumor and whether this pattern associates with clinical outcome. Methods. Paraffin embedded tumor tissues, obtained from SCLC patients who had no evidence of paraneoplastic autoimmune degeneration, were evaluated for SOX2 expression by immunohistochemistry for both intensity and extent of staining. Sera from the same patients were tested for autologous antibodies against recombinant SOX2 by enzyme-linked immunosorbent assay (ELISA). Correlates between overall survival and various clinical parameters including SOX2 staining and serology were determined. Results: SOX2 protein expression was observed in tumor tissue in 89% of patients. Seventeen patients (29%) were seropositive for SOX2 antibodies and, in contrast to SOX2 staining, the presence of antibody correlated with limited disease stage (p = 0.05). SOX2 seropositivity showed a significant association with the intensity of SOX2 staining in the tumor (p = 0.02) but not with the frequency of SOX2 expressing cells. Conclusion: Anti-SOX2 antibodies associate with better prognosis (limited stage disease) while SOX2 protein expression does not; similar to reports from some earlier studies. Our data provides an explanation for this seemingly contrasting data for the first time as SOX2 antibodies can be observed in patients whose tumors contain relatively few but strongly staining cells, thus supporting the possible presence of active immune-surveillance and immune-editing targeting SOX2 protein in this tumor type. © 2014 Atakan et al.; licensee BioMed Central Ltd

Propagation of a hole on a Neel background

We analyze the motion of a single hole on a N\'eel background, neglecting spin fluctuations. Brinkman and Rice studied this problem on a cubic lattice, introducing the retraceable-path approximation for the hole Green's function, exact in a one-dimensional lattice. Metzner et al. showed that the approximationalso becomes exact in the infinite-dimensional limit. We introduce a new approach to this problem by resumming the Nagaoka expansion of the propagator in terms of non-retraceable skeleton-paths dressed by retraceable-path insertions. This resummation opens the way to an almost quantitative solution of the problemin all dimensions and, in particular sheds new light on the question of the position of the band-edges. We studied the motion of the hole on a double chain and a square lattice, for which deviations from the retraceable-path approximation are expected to be most pronounced. The density of states is mostly adequately accounted for by the retra\-ce\-able-path approximation. Our band-edge determination points towards an absence of band tails extending to the Nagaoka energy in the spectrums of the double chain and the square lattice. We also evaluated the spectral density and the self-energy, exhibiting k-dependence due to finite dimensionality. We find good agreement with recent numerical results obtained by Sorella et al. with the Lanczos spectra decoding method. The method we employ enables us to identify the hole paths which are responsible for the various features present in the density of states and the spectral density.Comment: 26 pages,Revte

Flow Equations for U_k and Z_k

By considering the gradient expansion for the wilsonian effective action S_k of a single component scalar field theory truncated to the first two terms, the potential U_k and the kinetic term Z_k, I show that the recent claim that different expansion of the fluctuation determinant give rise to different renormalization group equations for Z_k is incorrect. The correct procedure to derive this equation is presented and the set of coupled differential equations for U_k and Z_k is definitely established.Comment: 5 page

Correlations in Ising chains with non-integrable interactions

Two-spin correlations generated by interactions which decay with distance r as r^{-1-sigma} with -1 <sigma <0 are calculated for periodic Ising chains of length L. Mean-field theory indicates that the correlations, C(r,L), diminish in the thermodynamic limit L -> \infty, but they contain a singular structure for r/L -> 0 which can be observed by introducing magnified correlations, LC(r,L)-\sum_r C(r,L). The magnified correlations are shown to have a scaling form F(r/L) and the singular structure of F(x) for x->0 is found to be the same at all temperatures including the critical point. These conclusions are supported by the results of Monte Carlo simulations for systems with sigma =-0.50 and -0.25 both at the critical temperature T=Tc and at T=2Tc.Comment: 13 pages, latex, 5 eps figures in a separate uuencoded file, to appear in Phys.Rev.

Critical behavior of three-dimensional magnets with complicated ordering from three-loop renormalization-group expansions

The critical behavior of a model describing phase transitions in 3D antiferromagnets with 2N-component real order parameters is studied within the renormalization-group (RG) approach. The RG functions are calculated in the three-loop order and resummed by the generalized Pade-Borel procedure preserving the specific symmetry properties of the model. An anisotropic stable fixed point is found to exist in the RG flow diagram for N > 1 and lies near the Bose fixed point; corresponding critical exponents are close to those of the XY model. The accuracy of the results obtained is discussed and estimated.Comment: 10 pages, LaTeX, revised version published in Phys. Rev.

On critical behavior of phase transitions in certain antiferromagnets with complicated ordering

Within the four-loop \ve expansion, we study the critical behavior of certain antiferromagnets with complicated ordering. We show that an anisotropic stable fixed point governs the phase transitions with new critical exponents. This is supported by the estimate of critical dimensionality $N_c^C=1.445(20)$ obtained from six loops via the exact relation $N_c^C={1/2} N_c^R$ established for the real and complex hypercubic models.Comment: Published versio