Events and Seminars

• 2025/08/12

Disertante: Gerardo Aldazábal, CAB - Instituto Balseiro

Título: A traversal of confined parameter ranges, islands, and archipelagos within the Heterotic Landscape

Resumen: Despite extensive efforts to identify models derived from string compactifications, many regions remain unexplored. One example involves heterotic compactifications with reduced-rank gauge groups. An extreme case consists of so-called 'islands' of rank zero, featuring pure supergravity. We outline a general formalism based on asymmetric orbifolds involving the special Leech lattice, to construct heterotic models with gauge group rank reduction. We present concrete examples in both 6 and 4 dimensions.

• 2025/07/01

Disertante: Dmitry Melnikov, Instituto Internacional de Física de Natal

Título: Topological QFTs and quantum entanglement

Resumen: In this talk, I will explain how topological quantum field theories (TQFTs) capture quantum correlations. First, I will introduce a TQFT model and discuss basic avatars of entanglement. Next, I will discuss a classification of entanglement and compare it with the most common classification by Stochastic Local Operations and Classical Communication. Special attention will be paid to the classical limit of the theory, in which the classification becomes particularly simple. Entropy inequalities will also be reviewed in this limit. If time permits, I will discuss possible lessons for holography and multipartite entanglement beyond TQFT. 

• 2025/06/17

Speaker: Esteban Roulet, CAB

Title: Centaurus A as the main source of ultrahigh-energy cosmic rays

Abstract: The possibility that a dominant fraction of the ultrahigh energy cosmic rays is due the single source Centaurus~A is discussed. We focus on the properties of the source spectrum and composition required to reproduce the observations, showing that the nuclei are strongly suppressed either by a rigidity dependent source cutoff or by the photodisintegration interactions with the cosmic microwave background at the giant dipole resonance. The very mild attenuation effects taking place at lower energies imply that the secondary nuclei produced in photodisintegration processes during propagation from this nearby source provide a small contribution. Given the moderate anisotropies observed, the deflections in extragalactic and Galactic magnetic fields should play a crucial role. The diffusion in extragalactic fields as well as the finite source lifetime significantly affect the shape of the observed spectrum. The cosmic-ray flux at tens of EeV is dominated by the CNO component, being actually better reproduced by a mixture of C and O nuclei rather than by just N, while heavier nuclei become dominant above 70~EeV. The cosmic ray flux at a few EeV should mostly result from a more isotropic light component associated with a population of extragalactic sources. The inclusion of the subdominant contribution of heavy nuclei from the Galactic component helps to reproduce the observations around 1~EeV. 

• 2025/06/10

Speaker: Juan Fernández, Instituto Balseiro

Title: Efectos indirectos de un nuevo quark vectorial a la escala TeV

Abstract: Los quarks vectoriales son una posible ventana hacia física más allá del Modelo Estándar, con implicancias directas para uno de los problemas fundamentales actuales: el problema de la jerarquía. En esta charla se discutirá la viabilidad de una extensión que incorpora un quark vectorial en la misma representación que el quark top right del Modelo Estándar, evaluando su impacto en observables sensibles a su presencia, a la luz de los datos experimentales actuales.

• 2025/06/03

Speaker: Facundo Rigatuso, Instituto Balseiro

Title: Dimensionalidad de la actividad neuronal en sistemas aleatorios no-lineales

Abstract: Recientes avances en la tecnología de medición de la actividad neuronal han permitido el registro simultáneo de la actividad de cientos de neuronas simultáneamente. Estos registros han revelado que la actividad neuronal se desarrolla en un espacio de dimensión muy reducida con respecto a la dimensión máxima posible, el número total de neuronas. Este comportamiento, cuya causa aún no se comprende por completo, tiene implicaciones opuestas según la dimensión: espacios de alta dimensión facilitan tareas de clasificación y regresión, mientras que una dimensión reducida potencia la capacidad de generalización ante estímulos no entrenados. Además, la dimensionalidad varía según el área cerebral y el estado funcional (reposo vs. estímulo). Para tratar de entender este fenómeno típicamente se trabaja con una dinámica lineal alrededor de un punto fijo estable con entrada de ruido blanco, donde la región de actividad adopta forma elipsoidal. Su dimensión efectiva se cuantifica mediante la dimensión de participación (DPR). En este trabajo pretendemos extender este análisis a sistemas no lineales. Resultados numéricos preliminares indican que, como en el caso lineal, la DPR decrece con el tamaño medio de los acoplamientos, pero la dependencia incluye ahora un factor de escaleo adicional que depende de las no-linealidades del sistema. Proponemos aplicar teoría de campos para derivar de forma autoconsistente el factor de escalamiento adicional en la DPR en la región estable y emplear técnicas de reducción de dimensionalidad local para caracterizar la dinámica en el régimen de acoplamiento fuerte, donde las trayectorias ocupan variedades de geometría compleja. Finalmente, planeamos incorporar herramientas del grupo de renormalización sobre modelos neuronales estocásticos con el fin de identificar clases de universalidad y posibles transiciones críticas en la dinámica neuronal.

• 2025/05/27

Speaker: Martín Sasieta, Brandeis U.

Title: Geometric modular flows in 2d CFT and beyond

Abstract: We study geometric modular flows in two-dimensional conformal field theories. We explore which states exhibit a geometric modular flow with respect to a causally complete subregion and, conversely, how to construct a state from a given geometric modular flow. Given suitable boundary conditions, we find that generic geometric modular flows in the Rindler wedge are conformally equivalent. Based on this insight, we show how conformal unitaries can be used to explicitly construct a state for each flow. We analyze these states, deriving general formulas for the energy density and entanglement entropy. We also consider geometric flows beyond the Rindler wedge setting, and in higher dimensions.

• 2025/04/29

Speaker: Javier Magan, CAB

Title: Random circuits in the black hole interior

Abstract: TBA

• 2025/04/15

Speaker: Jacqueline Caminiti, Perimeter Institute

Title: Geometric modular flows in 2d CFT and beyond

Abstract: We study geometric modular flows in two-dimensional conformal field theories. We explore which states exhibit a geometric modular flow with respect to a causally complete subregion and, conversely, how to construct a state from a given geometric modular flow. Given suitable boundary conditions, we find that generic geometric modular flows in the Rindler wedge are conformally equivalent. Based on this insight, we show how conformal unitaries can be used to explicitly construct a state for each flow. We analyze these states, deriving general formulas for the energy density and entanglement entropy. We also consider geometric flows beyond the Rindler wedge setting, and in higher dimensions.

• 2025/04/08

Speaker: Alejandro Rodríguez, UBA

Title: Exploring Double Field Theory with N=1 Supersymmetry

Abstract: The low-energy limit of superstring theories is described by ten-dimensional supergravity theories, whose effective actions receive perturbative corrections governed by powers of α′, a parameter associated with the string length. These corrections have profound implications for compactifications and gravitational solutions - key aspects of string phenomenology. A promising framework to study them is Double Field Theory (DFT), which incorporates string theory’s T-duality as a manifest symmetry. In this talk, I will present the N=1 supersymmetric extension of DFT and discuss its applications in heterotic supergravity, including: rhe role of non-geometric transformations (duality group) in determining the effective action; first-order α′-corrections in both DFT and heterotic supergravity; a generalization of the Kerr-Schild ansatz to DFT, providing a tool to construct supersymmetric solutions within the duality formalism. Finally, I will outline future research directions based on DFT and its potential to explore new scenarios in gravity and string theory.

• 2025/03/19

Speaker: Javier Moreno, Universidad de Concepción, Chile

Title: Higher-dimensional Willmore energy as holographic entanglement entropy

Abstract: The vacuum entanglement entropy of a general conformal field theory (CFT) in five dimensions contains a universal term, F(A), which has a complicated and non-local dependence on the geometric details of the region A and the theory. Analogously to the previously known three-dimensional case, we prove that for CFTs in five dimensions which are holographically dual to Einstein gravity, F(A) is equal to a four-dimensional version of the “Willmore energy” associated to a doubled and closed version of the Ryu-Takayanagi (RT) surface of A embedded in R^5. The Willmore energy is shown to arise from a conformal-invariant codimension-two functional obtained by evaluating six-dimensional conformal gravity on the conically-singular orbifold of the replica trick. The new functional involves an integral over the doubled RT surface of a linear combination of three quartic terms in extrinsic curvatures and is free from ultraviolet divergences by construction. We verify explicitly the validity of our new formula for various entangling regions and argue that, as opposed to the three-dimensional case, F (A) is not globally minimized by a round ball. Rather, F(A) can take arbitrarily positive and negative values as a function of A. Hence, we conclude that the round ball is not a global minimizer of F(A) for general five-dimensional CFTs.

• 2025/03/11

Speaker: Diana López Nacir, Departamento de Física, Facultad de Ciencias Exactas y Naturales, UBA

Title: Materia oscura vectorial ultraliviana, anisotropías y modos adiabáticos cosmológicos

Abstract: Los modelos de materia oscura ultraliviana han ganado interés recientemente debido a sus predicciones a escalas pequeñas. Sus masas pequeñas pueden permitirles comportarse como una colección de ondas, lo que lleva a fenómenos nuevos como una supresión en el espectro de potencia de masa en escalas pequeñas, la presencia de patrones de interferencia característicos y la formación de núcleos solitónicos. En esta charla consideraré un modelo donde la  materia oscura consiste de un campo vectorial ultraliviano (VFDM) con un campo de fondo homogéneo que apunta en una dirección dada.  Un  campo de fondo tal genera   anisotropías en el universo temprano, caracterizadas por una métrica de  Bianchi I,  que decaen rápidamente una vez que la masa del campo se vuelve comparable con la tasa de expansión del universo,   lo que los convierte en candidatos viables para la materia oscura. Presentaré resultados recientes sobre el estudio de la evolución del universo de fondo con VFDM y de las  perturbaciones cosmológicas a gran escala en el régimen lineal,  tales como los espectros de potencia de la materia definidos para vectores de onda con una dirección dada.

• 2025/03/05 

Speaker: Filipe Freire, Leiden University

Title: My physics from cosmic rays to viable cosmological inflation models

• 2025/02/25

Speaker: Esteban Roulet, CAB

Title: The most energetic neutrino at KM3NeT

• 2024/02/20

Speaker: Martín Schvellinger

Title: String theory and hadron structure 

• 2024/02/27 

Speaker: Roberto Emparan

Title: Tearing down spacetime with quantum entanglement

• 2024/03/12

Speaker: Marco Fabbrichesi

Title: Quantum entanglement and Bell inequality violation at colliders

• 2024/03/19

Speaker: Tom Banks

Title: A hydrodynamic approach to quantum gravity

• 2024/03/21

Speaker: Tom Banks

Title: Holographic inflationary cosmology

• 2024/03/25

Speaker: Sebastián Franchino-Viñas

Title: From trace anomaly to non-conformal theories

• 2024/03/26

Speaker: Suvrat Raju

Title: Massive particles at spatial infinity

• 2024/04/23

Speaker: Markus Frob

Title: Modular hamiltonians, relative entropy and the entropy-area law in de Sitter spacetime

• 2024/08/14

Speaker: Dam Thanh Son

Title: General-coordinate invariant theory of guiding center motion

• 2024/08/27

Speaker: Stephanie Baines

Title: Looking for R-symmetries using generalised geometry

• 2024/09/10

Speaker: Leandro Da Rold

Title: ¿Qué sabemos del bosón de Higgs?

• 2024/10/01

Speaker: Lucía Cabrera

Title: De teorías de campos stringy y simetrías ocultas

• 2024/10/22

Speaker: Horacio Casini

Title: Invariancia modular como completitud

• 2024/10/29

Speaker: Brandon Rayhaun

Title: On symmetries, boundaries and entanglement entropy

• 2024/11/05

Speaker: Mariana Graña

Title: String phenomenology in non-geometric backgrounds

• 2024/11/12

Speaker: Nicolás Abate

Title: Información cuántica e irreversibilidad en de Sitter

• 2024/11/25

Speaker: Roberto Trinchero

Title: QED positronium and the exact renormalization group

Instituto Balseiro's Colloquia