Publications

Order by: publication date number of citations

• Effect of next-nearest neighbor hopping on the single-particle excitations at finite temperature

  Harun Al Rashid, Dheeraj Kumar Singh

  SciPost Phys. 16, 107 (2024) · published 22 April 2024 | Toggle abstract · pdf

  In the half-filled one-orbital Hubbard model on a square lattice, we study the effect of next-nearest neighbor hopping on the single-particle spectral function at finite temperature using an exact-diagonalization + Monte-Carlo based approach to the simulation process. We find that the pseudogap-like dip, existing in the density of states in between the Néel temperature $T_N$ and a relatively higher temperature scale $T^*$, is accompanied with a significant asymmetry in the hole- and particle-excitation energy along the high-symmetry directions as well as along the normal-state Fermi surface. On moving from ($\pi/2, \pi/2$) toward $(\pi, 0)$ along the normal state Fermi surface, the hole-excitation energy increases, a behavior remarkably similar to what is observed in the $d$-wave state and pseudogap phase of high-$T_c$ cuprates, whereas the particle-excitation energy decreases. The quasiparticle peak height is the largest near ($\pi/2, \pi/2$) whereas it is the smallest near $(\pi, 0)$. These spectral features survive beyond $T_N$. The temperature window $T_N \lesssim T \lesssim T^*$ shrinks with an increase in the next-nearest neighbor hopping, which indicates that the next-nearest neighbor hopping may not be supportive to the pseudogap-like features.

• The Hoyle Family: break-up measurements to probe α-condensation in light nuclei

  Robin Smith, Jack Bishop, Joel Hirst, Tzany Kokalova, Carl Wheldon

  SciPost Phys. Proc. 3, 030 (2020) · published 26 February 2020 | Toggle abstract · pdf

  The 12C Hoyle state is a candidate for α-condensation, due to its large volume and α-cluster structure. This paper discusses precision break-up measurements and how they can elucidate α-condensate structures. Two experiments are discussed in detail, firstly concerning the break-up of 12C and then the decays of heavier nuclei. With more theoretical input, and increasingly complex detector setups, precision break-up measurements can, in principle, provide insight into the structures of states in α-conjugate nuclei. At present, such searches have not delivered evidence for α-condensation in 12C or 16O.

• Application of the JISP16 potential to the nucleon induced deuteron breakup process at E=13 MeV and E=65 MeV

  Volodymyr Soloviov1, Jacek Golak, Roman Skibiński, Kacper Topolnicki, and Henryk Witała

  SciPost Phys. Proc. 3, 032 (2020) · published 26 February 2020 | Toggle abstract · pdf

  The JISP16 nucleon-nucleon potential has been applied to investigations of the nucleon induced deuteron breakup reaction at the incoming nucleon laboratory energies E = 13 MeV and E = 65 MeV. We have found that for the studied process the JISP16 force gives a description of the exclusive cross section, which is generally similar to the ones obtained with the standard realistic nucleon-nucleon AV18 interaction. However, there are some regions of the phase space where the differential cross sections predicted by the JISP16 and AV18 models, differ by more than 100 %. These special kinematical configurations may possibly be useful to refit the JISP16 force parameters.

• An exact local mapping from clock-spins to fermions

  Simone Traverso, Christoph Fleckenstein, Maura Sassetti, Niccolò Traverso Ziani

  SciPost Phys. Core 6, 055 (2023) · published 15 August 2023 | Toggle abstract · pdf

  Clock-spin models are attracting great interest, due to both their rich phase diagram and their connection to parafermions. In this context, we derive an exact local mapping from clock-spin to fermionic partition functions. Such mapping, akin to techniques introduced by Fedotov and Popov for spin $\frac{1}{2}$ chains, grants access to well established numerical tools for the perturbative treatment of fermionic systems in the clock-spin framework. Moreover, in one dimension, it allows to use bosonization to access the low energy properties of clock-spin models. Finally, aside from the direct application in clock-spin models, this new mapping enables the conception of interesting fermionic models, based on the clock-spin counterparts.

• Measurements of $W$ and $Z/γ^*$ cross sections and their ratios in $pp$ collisions at STAR

  Jae Nam

  SciPost Phys. Proc. 8, 140 (2022) · published 14 July 2022 | Toggle abstract · pdf

  While the unpolarized parton distribution functions of the valence quarks ($d$ and $u$) are well determined from DIS experiments, the sea quark counterparts, $\bar{d}$ and $\bar{u}$, are much less constrained, in particular, near the valence region. Measurements of $W^+/W^-$ production ratio in $pp$ collider experiments, such as the STAR experiment at RHIC, can probe the $\bar{d}/\bar{u}$ ratio at a large $Q^2$ set by the $W$ mass. These proceedings will discuss recent results of $W$ and $Z$ cross-section measurements using the STAR $pp$ collision data at a center-of-mass energy of $\sqrt{s} = 500/510\;\mathrm{GeV}$ collected in 2011, 2012, 2013 and 2017.

• Recent progresses on BSM and dark matter searches with CUORE

  Antonio Branca on behalf of the CUORE Collaboration

  SciPost Phys. Proc. 12, 054 (2023) · published 5 July 2023 | Toggle abstract · pdf

  The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric $0\nu\beta\beta$ experiment to reach the one-tonne mass scale. The detector, located underground at the Laboratori Nazionali del Gran Sasso in Italy, consists of 988 TeO$_2$ crystals arranged in a compact cylindrical structure of 19 towers, operating at a base temperature of about 10 mK. After beginning its first physics data run in 2017, CUORE has since collected the largest amount of data ever acquired with a solid state detector and provided the most sensitive measurement of $0\nu\beta\beta$ decay in $^{130}$Te ever conducted. The large exposure, sharp energy resolution, segmented structure and radio-pure environment make CUORE an ideal instrument for a wide array of searches for rare events and symmetry violations. New searches for low mass dark matter, solar axions, CPT and Lorenz violations, and refined measurements of the $2\nu\beta\beta$ spectrum in CUORE have the potential to provide new insight and constraints on extensions to the standard model complementary to other particle physics searches. In this contribution, the recent progress on BSM and dark matter searches in CUORE are discussed.

• Fast tensor disentangling algorithm

  Kevin Slagle

  SciPost Phys. 11, 056 (2021) · published 13 September 2021 | Toggle abstract · pdf

  Many recent tensor network algorithms apply unitary operators to parts of a tensor network in order to reduce entanglement. However, many of the previously used iterative algorithms to minimize entanglement can be slow. We introduce an approximate, fast, and simple algorithm to optimize disentangling unitary tensors. Our algorithm is asymptotically faster than previous iterative algorithms and often results in a residual entanglement entropy that is within 10 to 40% of the minimum. For certain input tensors, our algorithm returns an optimal solution. When disentangling order-4 tensors with equal bond dimensions, our algorithm achieves an entanglement spectrum where nearly half of the singular values are zero. We further validate our algorithm by showing that it can efficiently disentangle random 1D states of qubits.

• Beryllium-9 in cluster effective field theory

  Elena Filandri, Paolo Andreatta, Carlo A. Manzata, Chen Ji, W. Leidemann, G. Orlandini

  SciPost Phys. Proc. 3, 034 (2020) · published 26 February 2020 | Toggle abstract · pdf

  We study the 9 Be ground-state energy with non-local αn and αα potentials derived from Cluster Effective Field Theory. The short-distance dependence of the interaction is regulated with a momentum cutoff. The potential parameters are fitted to reproduce scattering length and effective range. We implement such potential models in a Non-Symmetrized Hyperspherical Harmonics (NSHH) code in momentum space. In addition we calculate ground-state energies of various alpha nuclei. Work is in progress in view of the calculation of the photodisintegration of 9 Be with the Lorentz Integral Transform (LIT) method.

• Design constraints for Unruh-DeWitt quantum computers

  Eric W. Aspling, John A. Marohn, Michael J. Lawler

  SciPost Phys. Core 7, 019 (2024) · published 10 April 2024 | Toggle abstract · pdf

  The Unruh-DeWitt particle detector model has found success in demonstrating quantum information channels with non-zero channel capacity between qubits and quantum fields. These detector models provide the necessary framework for experimentally realizable Unruh-DeWitt quantum computers with near-perfect channel capacity. We propose spin-qubits with gate-controlled coupling to Luttinger liquids as a laboratory setting for Unruh-DeWitt detectors and explore general design constraints that underpin their feasibility in this and other settings. We present several experimental scenarios including graphene ribbons, edges states in the quantum spin Hall phase of HgTe quantum wells, and the recently discovered quantum anomalous Hall phase in transition metal dichalcogenides. Theoretically, through bosonization, we show that Unruh-DeWitt detectors can carry out quantum computations and identify when they can make perfect quantum communication channels between qubits via the Luttinger liquid. Our results point the way toward an all-to-all connected solid state quantum computer and the experimental study of quantum information in quantum fields via condensed matter physics.

• Rapid measurements and phase transition detections made simple by AC-GANs

  Jiewei Ding, Ho-Kin Tang, Wing Chi Yu

  SciPost Phys. Core 7, 035 (2024) · published 11 June 2024 | Toggle abstract · pdf

  In recent years, significant attention has been paid to using end-to-end neural networks for analyzing Monte Carlo data. However, the exploration of non-end-to-end generative adversarial neural networks remains limited. Here, we investigate classical many-body systems using generative adversarial neural networks. We employ the conditional generative adversarial network with an auxiliary classifier (AC-GAN) and integrate self-attention layers into the generator. This modification enables the network learn the distribution of the two-dimensional (2D) XY model's spin configurations and the physical quantities of interest. Utilizing the symmetry of the systems, we discover that AC-GAN can be trained with a very small raw dataset. This approach allows us to obtain reliable measurements for models typically demanding large samples, such as the large-sized 2D XY and the 3D constrained Heisenberg models. Moreover, we demonstrate the capability of AC-GAN to identify the phase transition points by quantifying the distribution changes in the spin configurations of the systems.