Community Detection with and without Prior Information (2009)
Allahverdyan, Armen E., Galstyan, Aram
We study the problem of graph partitioning, or clustering, in sparse networks with prior information about the clusters. Specifically, we assume that for a fraction $\rho$ of the nodes the true...
Thermodynamic efficiency of information and heat flow (2009)
Allahverdyan, Armen E., Janzing, Dominik, Mahler, Guenter
A basic task of information processing is information transfer (flow). Here we study a pair of Brownian particles each coupled to a thermal bath at temperature $T_1$ and $T_2$, respectively. The...
Optimal thermal refrigerator (2009)
Allahverdyan, Armen E., Hovhannisyan, Karen, Mahler, Guenter
We study a refrigerator model which consists of two $n$-level systems interacting via a pulsed external field. Each system couples to its own thermal bath at temperatures $T_h$ and $T_c$,...
Kinetics of the helix-coil transition (2009)
Allahverdyan, Armen E., Gevorkian, Sasun G., Simonian, Aleksandr
Based on the Zimm-Bragg model we study cooperative helix-coil transition driven by a finite-speed change of temperature. There is an asymmetry between the coil-to-helix and helix-to-coil transition:...
Replicators in Fine-grained Environment: Adaptation and Polymorphism (2009)
Allahverdyan, Armen E., Hu, Chin-Kun
Selection in a time-periodic environment is modeled via the two-player replicator dynamics. For sufficiently fast environmental changes, this is reduced to a multi-player replicator dynamics in a...
Quantum restrictions on transfer of matrix elements (2008)
Allahverdyan, Armen E., Hovhannisyan, Karen
We discuss restrictions imposed by quantum mechanics on the process of matrix elements transfer from the one system to another. This is relevant for various processes of partial state transfer...
Entropy of Hidden Markov Processes via Cycle Expansion (2008)
Hidden Markov Processes (HMP) is one of the basic tools of the modern probabilistic modeling. The characterization of their entropy remains however an open problem. Here the entropy of HMP is...
Employing feedback in adiabatic quantum dynamics (2008)
Allahverdyan, Armen E., Mahler, Guenter
We study quantum adiabatic dynamics, where the slowly moving field is influenced by system's state (feedback). The information for the feedback is gained from non-disturbating measurements done on an...
Work extremum principle: Structure and function of quantum heat engines (2007)
Allahverdyan, Armen E., Johal, Ramandeep S., Mahler, Guenter
We consider a class of quantum heat engines consisting of two subsystems interacting via a unitary transformation and coupled to two separate baths at different temperatures $T_h > T_c$. The purpose...
Relating the thermodynamic arrow of time to the causal arrow (2007)
Allahverdyan, Armen E., Janzing, Dominik
Consider a Hamiltonian system that consists of a slow subsystem S and a fast subsystem F. The autonomous dynamics of S is driven by an effective Hamiltonian, but its thermodynamics is unexpected. We...
The Quantum Measurement Process: Lessons from an Exactly Solvable Model (2007)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
The measurement of a spin-$\half$ is modeled by coupling it to an apparatus, that consists of an Ising magnetic dot coupled to a phonon bath. Features of quantum measurements are derived from the...
Phase transitions and quantum measurements (2005)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
In a quantum measurement, a coupling $g$ between the system S and the apparatus A triggers the establishment of correlations, which provide statistical information about S. Robust registration...
Dynamics of a quantum measurement (2004)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
We work out an exactly solvable hamiltonian model which retains all the features of realistic quantum measurements. In order to use an interaction process involving a system and an apparatus as a...
The quantum measurement process in an exactly solvable model (2004)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
An exactly solvable model for a quantum measurement is discussed which is governed by hamiltonian quantum dynamics. The $z$-component $\hat s_z$ of a spin-1/2 is measured with an apparatus, which...
Thomson's formulation of the second law for macroscopic and finite work sources (2004)
Armen E. Allahverdyan, Roger Balian, Theo M. Nieuwenhuizen
Abstract: Thomson's formulation of the second law states: no work can be extracted from an equilibrium system through a cyclic process. A simple, general proof is presented for the case of...
Thomson's formulation of the second law: an exact theorem and limits of its validity (2002)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
Thomson's formulation of the second law - no work can be extracted from a system coupled to a bath through a cyclic process - is believed to be a fundamental principle of nature. For the equilibrium...
Quantum Brownian motion and its conflict with the second law (2002)
Nieuwenhuizen, Theo M., Allahverdyan, Armen E.
The Brownian motion of a harmonically bound quantum particle and coupled to a harmonic quantum bath is exactly solvable. At low enough temperatures the stationary state is non-Gibbsian due to an...
Bath generated work extraction in two-level systems (2002)
Pombo, Claudia, Allahverdyan, Armen E., Nieuwenhuizen, Theo M.
The spin-boson model, often used in NMR and ESR physics, quantum optics and spintronics, is considered in a solvable limit to model a spin one-half particle interacting with a bosonic thermal bath....
Nieuwenhuizen, Theo M., Allahverdyan, Armen E.
The experimental verification of the Fluctuation Theorem by Wang et al. is not a violation but even a confirmation of the second law, resulting from their observations in a proper interpretation.
Curie-Weiss model of the quantum measurement process (2002)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
A hamiltonian model is solved, which satisfies all requirements for a realistic ideal quantum measurement. The system S is a spin-$\half$, whose $z$-component is measured through coupling with an...
Quantum measurement as driven phase transition: An exactly solvable model (2001)
Allahverdyan, Armen E., Balian, Roger, Nieuwenhuizen, Theo M.
A model of quantum measurement is proposed, which aims to describe statistical mechanical aspects of this phenomenon, starting from a purely Hamiltonian formulation. The macroscopic measurement...