# Effect of discrete breathers on the specific heat of a nonlinear chain

## TL;DR

This study investigates how discrete breathers influence the specific heat of a nonlinear chain, revealing that they can either reduce or increase specific heat depending on the type of anharmonicity.

## Contribution

It demonstrates the impact of discrete breathers on specific heat in nonlinear chains with different anharmonicities, a novel insight into energy localization effects.

## Key findings

- Discrete breathers affect the specific heat depending on anharmonicity type.
- Hard-type anharmonicity reduces specific heat with DBs.
- Soft-type anharmonicity increases specific heat with DBs.

## Abstract

A nonlinear chain with six-order polynomial on-site potential is used to analyze the evolution of the total to kinetic energy ratio during development of modulational instability of extended nonlinear vibrational modes. For the on-site potential of hard-type (soft-type) anharmonicity, the instability of $q=\pi$ mode ($q=0$ mode) results in the appearance of long-living discrete breathers (DBs) that gradually radiate their energy and eventually the system approaches thermal equilibrium with spatially uniform and temporally constant temperature. In the hard-type (soft-type) anharmonicity case, the total to kinetic energy ratio is minimal (maximal) in the regime of maximal energy localization by DBs. It is concluded that DBs affect specific heat of the nonlinear chain and for the case of hard-type (soft-type) anharmonicity they reduce (increase) the specific heat.