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We consider the problem of code design for a set of parallel correlated Rayleigh fading channels. This design problem arises whenever a channel can be decomposed into parallel channels, for example in OFDM schemes using Weyl-Heisenberg bases over underspread fading channels [1]. Schemes involving rotations of integer lattices have been proposed in [2] as a… (More)

- B. Bagchia, S. Mallik, C. Quesneb, R. Roychoudhuryc, Prafulla Chandra

We consider a PT-symmetric partner to Khare-Mandal’s recently proposed non-Hermitian potential with complex eigenvalues. Our potential, which is quasi-exactly solvable, is shown to possess only real eigenvalues. PACS : 03.65.Bz, 03.65.Ge

- S. Mallik
- 1994

It is shown that the chiral nonanalytic terms generated by ∆33 resonance in the nucleon self-energy is reproduced in chiral perturbation theory by perturbing appropriate local operators contained in the pion-nucleon effective Lagrangian itself.

The simplest purely imaginary and piecewise constant PT -symmetric potential located inside a larger box is studied. Unless its strength exceeds a certain critical value, all the spectrum of its bound states remains real and discrete. We interpret such a model as an initial element of the generalized non-Hermitian Witten’s hierarchy of solvable Hamiltonians… (More)

In the framework of SUSYQM extended to deal with non-Hermitian Hamiltonians, we analyze three sets of complex potentials with real spectra, recently derived by a potential algebraic approach based upon the complex Lie algebra sl(2,C). This extends to the complex domain the well-known relationship between SUSYQM and potential algebras for Hermitian… (More)

- Siddhartha Mallik, Ralf Koetter
- EURASIP J. Adv. Sig. Proc.
- 2006

We study the problem of modulation and coding for doubly dispersive, i.e., time and frequency selective fading channels. Using the recent result that under-spread linear systems are approximately diagonalized by biorthogonal Weyl-Heisenberg bases, we arrive at a canonical formulation of modulation and code design. For coherent reception with maximum… (More)

- S Mallik
- 1997

We extend an earlier, configuration space method to find the Wilson coefficients of operators appearing in the short distance expansion of thermal correlation functions of different quark bilinears. Considering all the different correlation functions, there arise, up to dimension four, two new operators, in addition to the two appearing already in the… (More)

- Sourav Sarkar, B. K. Patra, V. J. Menon, S. Mallik, Bidhan Nagar
- 2001

This is a short review on the thermal, spectral representation in the real-time version of the finite temperature quantum field theory. After presenting a clear derivation of the spectral representation, we discuss the properties of its spectral function. Two applications of this representation are then considered. One is the solution of the Dyson equation… (More)

An important topic in strong interaction at non-zero temperature is the calculation of shifts in the masses and the couplings which hadrons suffer while moving through a heat bath. Apart from their immediate relevance in understanding the experimental data on heavy ion collisions, these shifts as functions of temperature provide an effective description of… (More)

Thermal QCD sum rules generally bring in additional local operators over those already present in the vacuum sum rules. The thermal averages of these new operators are not immediately known. Here we write sum rules for correlation functions of odd chirality, which do not have this problem. We also evaluate one such sum rule for the thermal quark condensate.… (More)