5,345 research outputs found
Exact Quantum Many-Body Scar States in the Rydberg-Blockaded Atom Chain
A recent experiment in the Rydberg atom chain observed unusual oscillatory
quench dynamics with a charge density wave initial state, and theoretical works
identified a set of many-body "scar states" showing nonthermal behavior in the
Hamiltonian as potentially responsible for the atypical dynamics. In the same
nonintegrable Hamiltonian, we discover several eigenstates at \emph{infinite
temperature} that can be represented exactly as matrix product states with
finite bond dimension, for both periodic boundary conditions (two exact
states) and open boundary conditions (two states and one each ). This discovery explicitly demonstrates violation of strong
eigenstate thermalization hypothesis in this model and uncovers exact quantum
many-body scar states. These states show signatures of translational symmetry
breaking with period-2 bond-centered pattern, despite being in one dimension at
infinite temperature. We show that the nearby many-body scar states can be well
approximated as "quasiparticle excitations" on top of our exact scar
states, and propose a quasiparticle explanation of the strong oscillations
observed in experiments.Comment: Published version. In addition to (v2): (1) Add additional proofs to
the exact scar states and intuitions behind SMA and MMA to the appendices.
(2) Add entanglement scaling of SMA and MMA to the appendice
Explicit construction of quasi-conserved local operator of translationally invariant non-integrable quantum spin chain in prethermalization
We numerically construct translationally invariant quasi-conserved operators
with maximum range M which best-commute with a non-integrable quantum spin
chain Hamiltonian, up to M = 12. In the large coupling limit, we find that the
residual norm of the commutator of the quasi-conserved operator decays
exponentially with its maximum range M at small M, and turns into a slower
decay at larger M. This quasi-conserved operator can be understood as a dressed
total "spin-z" operator, by comparing with the perturbative Schrieffer-Wolff
construction developed to high order reaching essentially the same maximum
range. We also examine the operator inverse participation ratio of the
operator, which suggests its localization in the operator Hilbert space. The
operator also shows almost exponentially decaying profile at short distance,
while the long-distance behavior is not clear due to limitations of our
numerical calculation. Further dynamical simulation confirms that the
prethermalization-equilibrated values are described by a generalized Gibbs
ensemble that includes such quasi-conserved operator.Comment: 22 pages with 13 pages of main text, 9 figures and 5 appendices
(published version
Unified structure for exact towers of scar states in the AKLT and other models
Quantum many-body scar states are many-body states with finite energy density in non-integrable models that do not obey the eigenstate thermalization hypothesis. Recent works have revealed "towers" of scar states that are exactly known and are equally spaced in energy, specifically in the AKLT model, the spin-1 XY model, and a spin-1/2 model that conserves number of domain walls. We provide a common framework to understand and prove known exact towers of scars in these systems, by evaluating the commutator of the Hamiltonian and a ladder operator. In particular we provide a simple proof of the scar towers in the integer-spin 1d AKLT models by studying two-site spin projectors. Through this picture we deduce a family of Hamiltonians that share the scar tower with the AKLT model, and also find common parent Hamiltonians for the AKLT and XY model scars. We also introduce new towers of exact states, organized in a "pyramid" structure, in the spin-1/2 model through successive application of a non-local ladder operator
MiR-624-5p enhances cell resistance against cisplatin via PDGFRA/Stat3/PI3K axis in ovarian cancer
Purpose: The purpose of this study was to evaluate the role of miR-624-5p in ovarian cancer.Methods: MiR-624-5p expression in ovarian cancer {OC) cell lines and normal cells (NCs) was evaluated and compared the differential miR-624-5p in OC A2780 cells and cisplatin-resistant OC cell line (A2780/DDP). CCK-8 was used to evaluate changes in cell viability of the A2780 and A2780/DDP cell lines as well as silenced miR-624-5p. Western Blot examined the Stat3 and phosphorylated Pi3k. The binding between PDGFRA and miR-624-5p was predicted on Targetscan and verified through Luciferase Reporter Assay. The role of PDGFRA in A2780/DDP by overexpressing PDGFRA was evaluated by RT-qPCR and CCK-8 assays. RT-qPCR assay also measured miR-624-5p expression responsive to different dosages of cisplatin and CCK8 examined viability levels correspondingly. In addition, the interplay of PDGFRA and miR-624-5p by combined downregulation of both miR-624-5pand PDGFRA were evaluated.Results: OC cells had higher miR-624-5p expression than NCs but lower compared to cisplatinresistant A2780/DDP cells. A2780/DDP cells had higher viability than OC cell line A2780. Stat3 and phosphorylated PI3K were activated in A2780/DDP cells. Silencing miR-624-5p led to lower viability inA2780/DDP cells. miR-624-5p expression dropped as the cisplatin concentration increased, resulting in decreasing viability respectively. Luciferase Reporter assay validated the binding of miR-624-5p and PDGFRA in A2780/DDP cells. Overexpressed PDGFRA induced lower cell viability in A2780/DDP cells. Downregulation of PDGFRA partially restored the lowered viability and inhibited Stat3 as well as phosphorylated Pi3k induced by miR-624-5p inhibitor.Conclusion: MiR-624-5p could add to the cellular resistance to cisplatin in OC in-vitro model, which indicated that it might help unveil the mystery of drug-resistance in clinical stage of ovarian cancer.
Keywords: MiR-624-5p, resistance, cisplatin, PDGFRA/Stat3/PI3K, ovarian cance
Quasiparticle explanation of the weak-thermalization regime under quench in a nonintegrable quantum spin chain
The eigenstate thermalization hypothesis provides one picture of thermalization in a quantum system by looking at individual eigenstates. However, it is also important to consider how local observables reach equilibrium values dynamically. Quench protocol is one of the settings to study such questions. A recent numerical study [Bañuls, Cirac, and Hastings, Phys. Rev. Lett. 106, 050405 (2007)] of a nonintegrable quantum Ising model with longitudinal field under such a quench setting found different behaviors for different initial quantum states. One particular case called the “weak-thermalization” regime showed apparently persistent oscillations of some observables. Here we provide an explanation of such oscillations. We note that the corresponding initial state has low energy density relative to the ground state of the model. We then use perturbation theory near the ground state and identify the oscillation frequency as essentially a quasiparticle gap. With this quasiparticle picture, we can then address the long-time behavior of the oscillations. Upon making additional approximations which intuitively should only make thermalization weaker, we argue that the oscillations nevertheless decay in the long-time limit. As part of our arguments, we also consider a quench from a BEC to a hard-core boson model in one dimension. We find that the expectation value of a single-boson creation operator oscillates but decays exponentially in time, while a pair-boson creation operator has oscillations with a t^(−3/2) decay in time. We also study dependence of the decay time on the density of bosons in the low-density regime and use this to estimate decay time for oscillations in the original spin model
Out-of-time-ordered correlators in short-range and long-range hard-core boson models and Luttinger liquid model
We study out-of-time-ordered correlators (OTOCs) in hard-core boson models with short-range and long-range hopping and compare the results to the OTOCs in the Luttinger-liquid model. For density-density correlations, a related expectation value of the squared commutator starts at zero and decays back to zero after the passage of the wavefront in all three models, while the wavefront broadens as t^(1/3) in the short-range model and shows no broadening in the long-range model and the Luttinger-liquid model. For the boson creation operator, the corresponding commutator function shows saturation inside the light cone in all three models, with similar wavefront behavior as in the density-density commutator function, despite the presence of a nonlocal string in terms of Jordan-Wigner fermions. For the long-range model and the Luttinger-liquid model, the commutator function decays as a power law outside the light cone in the long-time regime when following different fixed-velocity rays. In all cases, the OTOCs approach their long-time values in a power-law fashion, with different exponents for different observables and short-range versus long-range cases. Our long-range model appears to capture exponents in the Luttinger-liquid model (which are found to be independent of the Luttinger parameter in the model). This conclusion also comes to bear on the OTOC calculations in conformal field theories, which we propose correspond to long-ranged models
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