This is a list of my preprints and publications in reversechronological order. You can use the buttons below to filter according to the various broad areas in which I have worked on.
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2022

2022
On the time dependence of holographic complexity for charged AdS black holes with scalar hair
Roberto Auzzi, Stefano Bolognesi, Eliezer Rabinovici, Fidel I. Schaposnik Massolo and
Gianni Tallarita
JHEP 2022
In the presence of a scalar hair perturbation, the Cauchy horizon of a ReissnerNordström black hole disappears and is replaced by the rapid collapse of the EinsteinRosen bridge, which leads to a Kasner singularity. We study the timedependence of holographic complexity, both for the volume and for the action proposals, in a class of models with hairy black holes. Volume complexity can only probe a portion of the black hole interior that remains far away from the Kasner singularity. We provide numerical evidence that the Lloyd bound is satisfied by the volume complexity rate in all the parameter space that we explored. Action complexity can instead probe a portion of the spacetime closer to the singularity. In particular, the complexity rate diverges at the critical time t_c for which the WheelerDeWitt patch touches the singularity. After the critical time the action complexity rate approaches a constant. We find that the Kasner exponent does not directly affect the details of the divergence of the complexity rate at t = t_c and the latetime behaviour of the complexity. The Lloyd bound is violated by action complexity at finite time, because the complexity rate diverges at t = t_c. We find that the Lloyd bound is satisfied by the asymptotic action complexity rate in all the parameter space that we investigated.

2022
Thermodynamic Bethe Ansatz past turning points: the (elliptic) sinhGordon model
Lucı́a Córdova, Stefano Negro and
Fidel I. Schaposnik Massolo
JHEP 2022
We analyze the Thermodynamic Bethe Ansatz (TBA) for various integrable Smatrices in the context of generalized TTbar deformations. We focus on the sinhGordon model and its elliptic deformation in both its fermionic and bosonic realizations. We confirm that the determining factor for a turning point in the TBA, interpreted as a finite Hagedorn temperature, is the difference between the number of bound states and resonances in the theory. Implementing the numerical pseudoarclength continuation method, we are able to follow the solutions to the TBA equations past the turning point all the way to the ultraviolet regime. We find that for any number k of resonances the pair of complex conjugate solutions below the turning point is such that the effective central charge is minimized. As k → ∞ the UV effective central charge goes to zero as in the elliptic sinhGordon model. Finally we uncover a new family of UV complete integrable theories defined by the bosonic counterparts of the Smatrices describing the Φ(1,3) integrable deformation of nonunitary minimal models M(2,2n+3).
2021

2021
Dynamics of global and local vortices with orientational moduli
JHEP 2021
The dynamics of both global and local vortices with nonAbelian orientational moduli is investigated in detail. Headon collisions of these vortices are numerically simulated for parallel, antiparallel and orthogonal internal orientations where we find interesting dynamics of the orientational moduli. A detailed study of the intervortex force is provided and a phase diagram separating Abelian and nonAbelian vortex types is constructed. Some results on scatterings with nonzero impact parameter and multivortex collisions are included.

2021
A Physaruminspired approach to the Euclidean Steiner tree problem
Scientific Reports 2021
This paper presents a novel biologicallyinspired exploreandfuse approach to solving a large array of problems. The inspiration comes from Physarum, a unicellular slime mold capable of solving the traveling salesman and Steiner tree problems. Besides exhibiting individual intelligence, Physarum can also share information with other Physarum organisms through fusion. These characteristics of Physarum imply that spawning many such organisms we can explore the problem space in parallel, each individual gathering information and forming partial solutions pertaining to a local region of the problem space. When the organisms meet, they fuse and share information, eventually forming one organism which has a global view of the problem and can apply its intelligence to find an overall solution to the problem. This approach can be seen as a “softer” method of divide and conquer. We demonstrate this novel approach, developing the Physarum Steiner Algorithm which is capable of finding feasible solutions to the Euclidean Steiner tree problem. This algorithm is of particular interest due to its resemblance to Physarum polycephalum, ability to leverage parallel processing, avoid obstacles, and operate on various shapes and topological surfaces including the rectilinear grid.
2019

2019
On volume subregion complexity in Vaidya spacetime
Roberto Auzzi, Giuseppe Nardelli,
Fidel I. Schaposnik Massolo,
Gianni Tallarita and Nicolò Zenoni
JHEP 2019
We study holographic subregion volume complexity for a line segment in the AdS3 Vaidya geometry. On the field theory side, this gravity background corresponds to a sudden quench which leads to the thermalization of the stronglycoupled dual conformal field theory. We find the timedependent extremal volume surface by numerically solving a partial differential equation with boundary condition given by the Hubeny–Rangamani–Takayanagi surface, and we use this solution to compute holographic subregion complexity as a function of time. Approximate analytical expressions valid at early and at late times are derived.

2019
Phases Of Melonic Quantum Mechanics
Frank Ferrari and
Fidel I. Schaposnik Massolo
Phys. Rev. D 2019
We explore in detail the properties of two melonic quantum mechanical theories which can be formulated either as fermionic matrix quantum mechanics in the new large D limit, or as disordered models. Both models have a mass parameter m and the transition from the perturbative large m region to the strongly coupled "blackhole" small m region is associated with several interesting phenomena. One model, with U(n)^2 symmetry and equivalent to complex SYK, has a line of firstorder phase transitions terminating, for a strictly positive temperature, at a critical point having nontrivial, nonmeanfield critical exponents for standard thermodynamical quantities. Quasinormal frequencies, as well as Lyapunov exponents associated with outoftimeordered fourpoint functions, are also singular at the critical point, leading to interesting new critical exponents. The other model, with reduced U(n) symmetry, has a quantum critical point at strictly zero temperature and positive critical mass m∗. For 0 < m < m∗, it flows to a new gapless IR fixed point, for which the standard scale invariance is spontaneously broken by the appearance of distinct scaling dimensions ∆+ and ∆− for the Euclidean twopoint function when t → +∞ and t → −∞ respectively. We provide several detailed and pedagogical derivations, including rigorous proofs or simplified arguments for some results that were already known in the literature.
2018

2018
Phase Diagram of Planar Matrix Quantum Mechanics, Tensor, and SachdevYeKitaev Models
Tatsuo Azeyanagi, Frank Ferrari and
Fidel I. Schaposnik Massolo
Phys. Rev. Lett. 2018
We compute the phase diagram of a U(N)^2×O(D) invariant fermionic planar matrix quantum mechanics [equivalently tensor or complex SachdevYeKitaev (SYK) models] in the new large D limit, dominated by melonic graphs. The SchwingerDyson equations can have two solutions describing either a high entropy, SYK blackholelike phase, or a low entropy one with trivial IR behavior. In the strongly coupled region of the masstemperature plane, there is a line of first order phase transitions between the high and low entropy phases. This line terminates at a new critical point which we study numerically in detail. The critical exponents are nonmean field and differ on the two sides of the transition. We also study purely bosonic unstable and stable melonic models. The former has a line of Kazakov critical points beyond which the SchwingerDyson equations do not have a consistent solution. Moreover, in both models the wouldbe SYKlike solution of the IR limit of the equations does not exist in the full theory.

2018
Roughening of kmer–growing interfaces in stationary regimes
M. D. Grynberg and
Fidel I. Schaposnik Massolo
Physical Review E Feb 2018
We discuss the steady state dynamics of interfaces with periodic boundary conditions arising from bodycentered solidonsolid growth models in 1+1 dimensions involving random aggregation of extended particles (dimers, trimers, ⋯, kmers). Roughening exponents as well as width and maximal height distributions can be evaluated directly in stationary regimes by mapping the dynamics onto an asymmetric simple exclusion process with ktype of vacancies. Although for k≥2 the dynamics is partitioned into an exponentially large number of sectors of motion, the results obtained in some generic cases strongly suggest a universal scaling behavior closely following that of monomer interfaces.
2016

2016
Integrabilidad en la correspondencia AdS/CFT
Fidel I. Schaposnik Massolo
Physical Review E Aug 2016
2015

2015
Ladder exponentiation for generic large symmetric representation Wilson loops
JHEP Aug 2015
A recent proposal was made for a large representation rank limit for which the expectation values of N= 4 super YangMills Wilson loops are given by the exponential of the 1loop result. We verify the validity of this exponentiation in the strong coupling limit using the holographic D3brane description for straight Wilson loops following an arbitrary internal space trajectory.

2015
Cusped Wilson lines in symmetric representations
JHEP Aug 2015
We study the cusped Wilson line operators and Bremsstrahlung functions associated to particles transforming in the rankk symmetric representation of the gauge group U(N) for N=4 super YangMills. We find the holographic D3brane description for Wilson loops with internal cusps in two different limits: small cusp angle and k λ^½ ≫ N. This allows for a nontrivial check of a conjectured relation between the Bremsstrahlung function and the expectation value of the ½ BPS circular loop in the case of a representation other than the fundamental. Moreover, we observe that in the limit of k ≫ N, the cusped Wilson line expectation value is simply given by the exponential of the 1loop diagram. Using group theory arguments, this eikonal exponentiation is conjectured to take place for all Wilson loop operators in symmetric representations with large k, independently of the contour on which they are supported.
2014

2014
Reformulating the TBA equations for the quark antiquark potential and their two loop expansion
Zoltán Bajnok, János Balog,
Diego H. Correa, Árpád Hegedüs,
Fidel I. Schaposnik Massolo and Gábor Zsolt Tóth
JHEP Aug 2014
The boundary thermodynamic Bethe Ansatz (BTBA) equations introduced in arXiv:1203.1913 and arXiv:1203.1617 to describe the cusp anomalous dimension contain imaginary chemical potentials and singular boundary fugacities, which make its systematic expansion problematic. We propose an alternative formulation based on real chemical potentials and additional source terms. We expand our equations to double wrapping order and find complete agreement with the direct twoloop gauge theory computation of the cusp anomalous dimension.
2013

2013
D5brane boundary reflection factors
JHEP Aug 2013
We compute the strong coupling limit of the boundary reflection factor for excitations on open strings attached to various kinds of D5branes that probe AdS(5)×S(5). We study the crossing equation, which constrains the boundary reflection factor, and propose that some solutions will give the boundary reflection factors for all values of the coupling. Our proposal passes various checks in the strong coupling limit by comparison with diverse explicit string theory computations. In some of the cases we consider, the D5branes correspond to Wilson loops in the kth rank antisymmetric representation of the dual field theory. In the other cases they correspond in the dual field theory to the addition of a fundamental hypermultiplet in a defect.