In a series of papers [1, 2, 3], the author exactly diagonalized the truncated Hamiltonian Hc , proposed by Bogoliubov [4, 5], as a low energy approximation for the weakly interacting boson gas. In addition to the well know collective excitations (CEs) resulting from the Bogoliubov Canonic Approximation (BCA) [6, 7], and denoted as quasi-phonons (QPs), the exact eigenstates of Hc exhibit a new kind of CEs (the `hidden side' which the title alludes to), that we denote as vacuons. Those CEs are created/annihilated by adsorp-tion/emission of a quantum of energy twice as large as the activation energy of a QP. Being momentless, they are reminiscent of Cooper pairs of bosons, with opposite moments. The e_ects of the vacuons on the dynamics of the gas are discussed, with their possible exper-imental evidence.In a series of papers [1, 2, 3], the author exactly diagonalized the truncated Hamiltonian Hc , proposed by Bogoliubov [4, 5], as a low energy approximation for the weakly interacting boson gas. In addition to the well know collective excitations (CEs) resulting from the Bogoliubov Canonic Approximation (BCA) [6, 7], and denoted as quasi-phonons (QPs), the exact eigenstates of Hc exhibit a new kind of CEs (the `hidden side' which the title alludes to), that we denote as vacuons. Those CEs are created/annihilated by adsorp-tion/emission of a quantum of energy twice as large as the activation energy of a QP. Being momentless, they are reminiscent of Cooper pairs of bosons, with opposite moments. The e_ects of the vacuons on the dynamics of the gas are discussed, with their possible exper-imental evidence.

Advances in Materials Science and EngineeringMar 3, 20180 citations

The Excitation Spectrum for Weakly Interacting Bosons

Robert Seiringer

arXiv:1008.5349Communications in Mathematical PhysicsMay 13, 2011112 citations

Disordered bosons: Critical phenomena and evidence for new low energy excitations

M. S. Makivić, Nandini Trivedi, Salman Ullah

We study the T=0 critical properties of the superfluid-insulator transition in 2D hard core Bose systems with disorder. Using quantum Monte Carlo simulations and finite size scaling on 64\ifmmode\times\else\texttimes\fi{}64 lattices we find the dynamical exponent z=0.5\ifmmode\pm\else\textpm\fi{}0.1 and the correlation length exponent \ensuremath{\nu}=2.2\ifmmode\pm\else\textpm\fi{}0.2. At the transition, the system is metallic with a conductivity ${\mathrm{\ensuremath{\sigma}}}_{\mathit{c}}$=(1.2\ifmmode\pm\else\textpm\fi{}0.2)( ${\mathit{e}}^{\mathrm{*}}$ ${)}^{2}$ /h and a nonzero compressibility \ensuremath{\kappa}\ensuremath{\ne}0. These conclusions differ from the existing scaling theory as well as from simulations on simplified models argued to be in the same universality class. Our results are suggestive of new low lying collective excitations (modified from usual phonons) in the disordered system.We study the T=0 critical properties of the superfluid-insulator transition in 2D hard core Bose systems with disorder. Using quantum Monte Carlo simulations and finite size scaling on 64\ifmmode\times\else\texttimes\fi{}64 lattices we find the dynamical exponent z=0.5\ifmmode\pm\else\textpm\fi{}0.1 and the correlation length exponent \ensuremath{\nu}=2.2\ifmmode\pm\else\textpm\fi{}0.2. At the transition, the system is metallic with a conductivity ${\mathrm{\ensuremath{\sigma}}}_{\mathit{c}}$=(1.2\ifmmode\pm\else\textpm\fi{}0.2)(${\mathit{e}}^{\mathrm{*}}$${)}^{2}$/h and a nonzero compressibility \ensuremath{\kappa}\ensuremath{\ne}0. These conclusions differ from the existing scaling theory as well as from simulations on simplified models argued to be in the same universality class. Our results are suggestive of new low lying collective excitations (modified from usual phonons) in the disordered system.

Physical Review LettersOct 4, 199394 citations

Dynamic response of trapped ultracold bosons on optical lattices

G. G. Batrouni, Fakher F. Assaad, Richard T. Scalettar +1 more

We study the dynamic response of ultracold bosons trapped in one-dimensional optical lattices using Quantum Monte Carlo simulations of the boson Hubbard model with a confining potential. The dynamic structure factor reveals the inhomogeneous nature of the low temperature state, which contains coexisting Mott insulator and superfluid regions. We present new evidence for local quantum criticality and discuss implications for the experimental excitation spectrum of $^{87}\mathrm{Rb}$ atoms confined in one dimension.We study the dynamic response of ultracold bosons trapped in one-dimensional optical lattices using Quantum Monte Carlo simulations of the boson Hubbard model with a confining potential. The dynamic structure factor reveals the inhomogeneous nature of the low temperature state, which contains coexisting Mott insulator and superfluid regions. We present new evidence for local quantum criticality and discuss implications for the experimental excitation spectrum of $^{87}\mathrm{Rb}$ atoms confined in one dimension.

arXiv:cond-mat/0503371Physical Review ASep 14, 200545 citations

{\mathit{e}}^{\mathrm{*}}

{)}^{2}

/h and a nonzero compressibility \ensuremath{\kappa}\ensuremath{\ne}0. These conclusions differ from the existing scaling theory as well as from simulations on simplified models argued to be in the same universality class. Our results are suggestive of new low lying collective excitations (modified from usual phonons) in the disordered system.

^{87}\mathrm{Rb}

atoms confined in one dimension.