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Sher Alam

Publications and source records attributed to Sher Alam.

22 records · Page 2Linked to original sources

Theoretical modeling for quantum liquids from 1d to 2d dimensional crossover using quantum groups

Recent experimental and theoretical work in strongly correlated electron system necessitates a formulation to deal with 1d to 2d dimensional crossover and raises several interesting questions. A particularly interesting question is what happens to the 1d Luttinger liquid, as we go from 1d to 2d? The main point of emphasis of the present note is that the transition from 1d to 2d has an underlying quantum group symmetry. This relationhip of 1d to 2d transition with quantum group symmetry ties in nicely with our previous proposal to model superconductivity, antiferromagnetism and related phases arising from strongly correlated electron states with quantum groups. A simple model based on two interacting chains with nearest neighbor and next to nearest neighbor interactions is suggested. It appears reasonable to assume that it is the interaction between the 1d Luttinger liquids which leads to the quantum group symmetry and the transition to 2d quantum liquid. The conditions under which this 2d quantum liquid deviates away from the 2d Fermi liquid is clearly of main interest to us. One of the prime motivations underlying our proposal is the experimental observation of stripe structure [phase] in high T_c superconductivity [HTSC] materials. In short a simple model of two coupled chains 1d chains is considered to answer an important question, how does one couple two 1d chains [Luttinger Liquid] to obtain non-Fermi liquid [NFL] or partial NFL behavior in 2d?

cond-mat.str-el↗

Quantum Group based Modelling for the description of high temperature superconductivity and antiferromagnetism

Following our recent conjecture to model the phenomenona of antiferromagnetism and superconductivity by quantum symmetry groups, we propose in the present note three toy models, namely, one based on $SO_{q}(3)$ the other two constructed with the $SO_{q}(4)$ and $SO_{q}(5)$ quantum groups. Possible motivations and rationale for these choices are outlined. One of the prime motivations underlying our proposal is the experimental observation of stripe structure [phase] in high T_c superconductivity [HTSC] materials. A number of experimental techniques have recently observed that the CuO_2 are rather inhomogeneous, providing evidence for phase separation into a two component system. i.e. carrier-rich and carrier-poor regions. In particular, extended x-ray absorption fine structure [EXAFS] demonstrated that these domains forms stripes of undistorted and distorted local structures alternating with mesoscopic length scale comparable with coherence length in HTSC.

cond-mat↗

A Conjecture for possible theory for the description of high temperature superconductivity and antiferromagnetism

Keeping in mind some salient features of quantum symmetry groups and in lieu of the interesting critique by Baskaran and Anderson of the hypothesis of the SO(5) model of Zhang and the related works of others such as Sachdev to describe superconductivity and antiferromagnetism we propose a conjecture to model these complex phenomenona by quantum groups, at least as a starting point.

cond-mat↗

Sum rules for $e^+e^- \to W^+W^-$ helicity amplitudes from BRS invariance

The BRS invariance of the electroweak gauge theory leads to relationships between amplitudes with external massive gauge bosons and amplitudes where some of these gauge bosons are replaced with their corresponding Nambu-Goldstone bosons. Unlike the equivalence theorem, these identities are exact at all energies. In this paper we discuss such identities which relate the process $e^+e^- \to W^+W^-$ to $W^\pmχ^\mp$ and $χ^+χ^-$ production. By using a general form-factor decomposition for $e^+e^- \to W^+W^-$, $e^+e^- \to W^\pm χ^\mp$ and $e^+e^- \to χ^+χ^-$ amplitudes, these identities are expressed as sum rules among scalar form factors. Because these sum rules may be applied order by order in perturbation theory, they provide a powerful test of higher order calculations. By using additional Ward-Takahashi identities we find that the various contributions are divided into separately gauge-invariant subsets, the sum rules applying independently to each subset. After a general discussion of the application of the sum rules we consider the one-loop contributions of scalar-fermions in the Minimal Supersymmetric Standard Model as an illustration.

hep-ph↗