Integrable S matrix, mirror TBA and spectrum for the stringy AdS3×S3×S3×S1\text{AdS}_{3}\times\text{S}^3\times\text{S}^3\times\text{S}^1 WZW model

We compute the tree-level bosonic S matrix in light-cone gauge for superstrings on pure-NSNS $\text{AdS}_{3}\times\text{S}^3\times\text{S}^3\times\text{S}^1$. We show that it is proportional to the identity and that it takes the same form as for $\text{AdS}_{3} \times \text{S}^3\times\text{T}^4$ and for flat space. Based on this, we make a conjecture for the exact worldsheet S matrix and derive the mirror thermodynamic Bethe ansatz (TBA) equations describing the spectrum. Despite a non-trivial vacuum energy, they can be solved in closed form and coincide with a simple set of Bethe ansatz equations - again much like $\text{AdS}_{3}\times\text{S}^3\times\text{T}^4$ and flat space. This suggests that the model may have an integrable spin-chain interpretation. Finally, as a check of our proposal, we compute the spectrum from the worldsheet CFT in the case of highest-weight representations of the underlying Ka\v{c}-Moody algebras, and show that the mirror-TBA prediction matches it on the nose.Comment: 38 pages, Version accepted for publication in JHE

Integrable spin chain for stringy Wess-Zumino-Witten models

Building on arXiv:1804.01998 we investigate the integrable structure of the Wess-Zumino-Witten (WZW) model describing closed strings on $AdS_3\times S^3\times T^4$. Using the recently-proposed integrable S matrix we show analytically that all wrapping corrections cancel and that the theory has a natural spin-chain interpretation. We construct the integrable spin chain and discuss its relation with the WZW description. Finally we compute the spin-chain spectrum in closed form and show that it matches the WZW prediction on the nose.Comment: 46 pages, 3 figures, 9 tables; misprints corrected, references adde

Stress-energy tensor correlators from the world-sheet

The large $N$ limit of symmetric orbifold theories was recently argued to have an AdS/CFT dual world-sheet description in terms of an $\mathfrak{sl}(2,\mathbb{R})$ WZW model. In previous work the world-sheet state corresponding to the symmetric orbifold stress-energy tensor was identified. We calculate certain 2- and 3-point functions of the corresponding vertex operator on the world-sheet, and demonstrate that these amplitudes reproduce exactly what one expects from the dual symmetric orbifold perspective.Comment: 16+9 page

Evaluating the impact of eDoS attacks to cloud facilities

The complexity of modern cloud facilities requires attentive management policies that should encompass all aspects of the system. Security is a critical issue, as intrusions, misuse or denial of service attacks may damage both the users and the cloud provider including its reputation on the market. Disruptive attacks happen fast, cause evident and short term damages and are usually the result of operations that are hard to disguise. On the other hand, Energy oriented Denial of Service (eDoS) attacks aim at producing continuous minor damages, eventually with long term consequences. These long lasting attacks are difficult to detect. In this paper we model and analyse the behaviour of a system under eDoS attack. We study the impact in terms of cloud energy consumption of an attack strategy previously proposed in the literature and compare it with other strategies that we propose. Our findings show that the strategy previously proposed in the literature, based on keeping the cloud close to saturation, is not optimal (from the point of view of the attacker) in presence of non-constant workload and that there is a trade-off between the aggressiveness of the attacker and the duration of the attack in order to maximise the damage

Free field world-sheet correlators for AdS3{\rm AdS}_3

We employ the free field realisation of the $\mathfrak{psu}(1,1|2)_1$ world-sheet theory to constrain the correlators of string theory on ${\rm AdS}_3\times {\rm S}^3\times \mathbb{T}^4$ with unit NS-NS flux. In particular, we directly obtain the unusual delta function localisation of these correlators onto branched covers of the boundary ${\rm S}^2$ by the (genus zero) world-sheet -- this is the key property which makes the equivalence to the dual symmetric orbifold manifest. In our approach, this feature follows from a remarkable `incidence relation' obeyed by the correlators, which is reminiscent of a twistorial string description. We also illustrate our results with explicit computations in various special cases.Comment: 42 page

Conferimento della Laurea magistrale ad honorem in scienze archivistiche e biblioteconomiche a Michele Casalini / Award of the Laurea magistrale ad honorem in Library and information Science to Michele Casalini

On the 21st May 2019, the University of Florence awarded Michele Casalini an honorary degree for his dedication and his important contribution in the field of Library and Archival Sciences. The ceremony, which was held in the Rectorate's Aula Magna in Florence, represents the first recognition of merit for modern library science and the second for library and archival sciences to ever be granted by an Italian university. The text features the complete speeches by Luigi Dei, Rector, by Andrea Zorzi, Director of the SAGAS Department, the Laudatio by Mauro Guerrini, president of the Degree in Library and Archival Sciences and the Lectio Doctoralis by Michele Casalini, entitled La centralità delle biblioteche per il progresso e la democrazia. All the texts are published in Italian and English