Transport properties of continuous-time quantum walks on Sierpinski fractals

We model quantum transport, described by continuous-time quantum walks (CTQW), on deterministic Sierpinski fractals, differentiating between Sierpinski gaskets and Sierpinski carpets, along with their dual structures. The transport efficiencies are defined in terms of the exact and the average return probabilities, as well as by the mean survival probability when absorbing traps are present. In the case of gaskets, localization can be identified already for small networks (generations). For carpets, our numerical results indicate a trend towards localization, but only for relatively large structures. The comparison of gaskets and carpets further implies that, distinct from the corresponding classical continuous-time random walk, the spectral dimension does not fully determine the evolution of the CTQW.Comment: 10 pages, 6 figure

Individually selected teletherapy technique for accelerated partial breast irradiation

Background: The aim of the study was to individualize accelerated partial breast irradiation based on optimal dose distribution, protect risk organ and predict most advantageous technique. Materials and methods: 138 breast cancer patients receiving postoperative APBI were enrolled. APBI plans were generated using 3D-conformal (3D-CRT), sliding window intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). In the case of superficial tumours, additional plans were developed by adding electron beam. To planning target volume (PTV) 37.5 Gy/10 fractions, 1 fraction/day was prescribed. A novel plan quality index (PQI) served as the basis for comparisons. Results: IMRT was the most advantageous technique regarding homogeneity. VMAT provided best conformity, 3D-CRT — the lowest lung and heart exposure. PQI was the best in 45 (32.61%) VMAT, 13 (9.42%) IMRT, 9 (6.52%) 3D-CRT plans. In 71 cases (51.45%) no difference was detected. In patients with large PTV, 3D-CRT was the most favourable. Additional electron beam improved PQI of 3D-CRT plans but had no meaningful effect on IMRT or VMAT. IMRT was superior to VMAT if the tumour was superficial (p < 0.001), situated in the medial (p = 0.032) or upper quadrant (p = 0.046). Conclusions: In half of all cases, individually selected teletherapy techniques provide superior results over others; relevance of a certain technique may be predicted by volume and PTV localization

Time evolution of continuous-time quantum walks on dynamical percolation graphs

We study the time evolution of continuous-time quantum walks on randomly changing graphs. At certain moments edges of the graph appear or disappear with a given probability as in percolation. We treat this problem in a strong noise limit. We focus on the case when the time interval between subsequent changes of the graph tends to zero. We derive explicit formulae for the general evolution in this limit. We find that the percolation in this limit causes an effective time rescaling. Independently of the graph and the initial state of the walk, the time is rescaled by the probability of keeping an edge. Both the individual trajectories for a single system and average properties with a superoperator formalism are discussed. We give an analytical proof for our theorem and we also present results from numerical simulations of the phenomena for different graphs. We also analyze the effect of finite step-size on the evolution

A turizmus munkaerő-helyzete a pandémia után

A turizmus a világgazdaság egyik legjelentősebb szektora. A foglalkoztatottak közül minden 11. ember itt talál munkát. A Covid-19 óriási károkat okozott a szektornak, sok millió munkavállaló elhagyta az ágazatot. Magyarországon is kulcskérdés a munkaerő-hiány. Vajon meg lehet-e oldani ezeket a problémákat, és van-e esély a szektor vonzerejének visszaállítására. Az EU részbeni finanszírozásában megvalósuló Next Tourism Generation projekt esélyt jelenthet a probléma megoldására