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**Subject:** ELFT HÍRADÓ

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**From**: Andras Palyi <palyi AT mail.bme.hu>**To**: FIZINFO AT lists.kfki.hu**Subject**: [Fizinfo] Balazs Hetenyi's talk at BME next Monday**Date**: Fri, 25 Oct 2019 16:26:31 +0200

Dear Colleagues,

Next Monday Balazs Hetenyi will give a talk at the BME Exotic Quantum Phases

seminar.

Speaker: Balazs Hetenyi (Bilkent & BME)

Title: Superfluid weight and polarization amplitude in the one-dimensional

bosonic Hubbard model

Time: Oct 28, Monday, 14:00 (sharp)

Location: seminar room of the theory department (Department of Theoretical

Physics, Building F, stairway III., 1111 Budapest, Budafoki ut 8.)

Abstract: "We calculate the superfluid weight and the polarization amplitude

for the one-dimensional bosonic Hubbard model focusing on the strong-coupling

regime. Other than analytic calculations we apply two methods: variational

Monte Carlo based on the Baeriswyl wave function and exact diagonalization.

The former gives zero superfluid response at integer filling, while the

latter gives a superfluid response at finite hopping. From the polarization

amplitude we derive the variance and the associated size scaling exponent.

Again, the variational study does not produce a finite superfluid weight at

integer filling (size scaling exponent is near one), but the Fourier

transform of the polarization amplitude behaves in a similar way to the

result of exact diagonalization, with a peak at small hopping, and suddenly

decreasing at the insulator-superfluid transition. On the other hand, exact

diagonalization studies result in a finite spread of the total position which

increases with the size of the system. In the superfluid phase the size

scaling exponent is two as expected. Importantly, our work addresses the

ambiguities that arise in the calculation of the superfluid weight in

variational calculations, and we comment on the prediction of Anderson about

the superfluid response of the model at integer filling."

Best regards,

Andras Palyi

**[Fizinfo] Balazs Hetenyi's talk at BME next Monday**,*Andras Palyi, 10/25/2019*

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