REF 2026 is the 13th edition in the series of workshops on Resummation, Evolution and Factorization. The workshop brings together specialists in different areas, from effective field theory to lattice to QCD factorization methods. It will be held at the Instituto Galego de Física de Altas Enerxías (IGFAE) from the University of Santiago de Compostela (Galicia, NW Spain).

Iberian Strings 2026 is the eighteenth edition of the annual meeting of the Spanish and Portuguese communities working on String Theory. 

Recent developments in supergravity, strings, branes, gauge theories and related topics will be discussed.

Directors: Xabier Cid Vidal, Titus Mombächer

Supervisor/s: Cibrán Santamarina Ríos, Elena González Ferreiro

Tutor: Elena González Ferreiro

Tribunal members:

- President: Dr./Dra. .Begoña De La Cruz Martínez. CIEMAT-CSIC

- Secretary: Abraham Antonio Gallas Torreira. Universidade de Santiago de Compostela

- Member: Benjamin Frédéric Didier Audurier. Commisariat à l\\\\\\\'ÉnergieAtomique el aux Énergies Alternatives (CEA)

The open quantum system framework allows one to compute quarkonium`s evolution in a medium, keeping track of the needed quantum features. However, computing this evolution is a computationally demanding task. QTRAJ is an efficient code that allows one to simulate the behavior of quarkonium in a medium in the case in which the medium sees quarkonium as a small color dipole rT << 1. While this limit is accurate for Upsilon(1S), its applicability to other quarkonium states is unclear. 

In this talk, we present a generalization of this code that incorporates the regime where rT ~ 1 in the one-gluon exchange approximation. In its new version, QTRAJ implements new jump operators connecting different states, which are then expanded in plane waves, giving rise to a variation of the algorithm present in QTRAJ 1.0 where jumps with Delta l > 1 are allowed. We will show a review of this approach comparing the rT << 1 and rT ~ 1 cases, and we present preliminary phenomenological results.

Zoom link: https://us06web.zoom.us/j/87201065290?pwd=NgcwZ0kLMZufKachaFRHOlpLHgaIdB.1

Mass estimates of white dwarfs via electromagnetic methods, often differ from those obtained through gravitational redshift measurements, in some cases with discrepancies ranging in the 5-15% range across independent datasets.

Although many of the discrepancies reported in large spectroscopic surveys and confirmed by high-precision techniques such as astrometric microlensing and wide-binary analyses may be attributable to thermal effects, model uncertainties or measurement errors prevent a complete description of some of the observations.

Here, we explore an alternative explanation based on the presence of a gravitationally coupled bosonic scalar field that contributes to the stellar mass while remaining electromagnetically invisible. We construct stationary, static mixed configurations consisting of a white dwarf that presents a bosonic scalar field (dark matter) component, forming a composite white dwarf–boson star system. We explore families of solutions showing that a scalar field fraction of 5-15% to the mass contribution can account for the observed redshift excess. Our models provide a physically motivated explanation for the mass bias, might offer new observational signatures, and allow us to place preliminary constraints on the mass and compactness of the scalar field configuration. Finally, using our theoretical framework in combination with Bayesian model selection we provide plausible bounds for the mass of the constituent (ultralight) bosonic particle.

This workshop brings together the international community working on solenoidal spectrometers to discuss recent advances and future directions. We aim to showcase high-quality contributions that reflect the current state of the art, both in terms of physics cases and instrumentation developments.

Through a combination of invited talks, selected oral presentations, and posters, the program will highlight the most relevant and impactful work in the field. We look forward to your participation in fostering fruitful discussions and new collaborations.

The workshop will cover a broad range of topics, including:

• Physics with solenoidal spectrometers – applications in experimental studies with emphasis on low-energy nuclear physics.
• Technology and operation of solenoidal spectrometers – active targets (e.g., TPCs), silicon detector systems, and other detection technologies.
• Data acquisition systems – architecture, design, and integration for complex experiments.
• Data analysis techniques and software tools – methods for event reconstruction, calibration, and interpretation.
• Theoretical aspects in low-energy nuclear physics – state-of-the-art models and frameworks.

More info at: https://indico.global/event/15272/

The pygmy dipole resonance (PDR) refers to a low-lying strength in the dipole response of nuclei, located near the neutron separation energy and linked to the neutron excess in nuclei. Initially interpreted as an oscillation of the neutron skin against a symmetric core, many questions remain open concerning its fine structure, highlighting the need for new experimental data to pin down its nature and refine theoretical models.

In experimental studies of the PDR, so-called multi-messenger investigations show clear advantages, as different probes provide complementary information on its nature. My PhD work fitted into this context and offered, for the first time, a study of the PDR using a neutron probe. The experiment was conducted in 2022 at the Neutrons For Science facility at GANIL-SPIRAL2 and was dedicated to the study of the PDR in the ¹⁴⁰Ce nucleus via neutron inelastic scattering (n,n’γ). The PARIS and MONSTER arrays were used for the γ-ray and scattered neutron detection, respectively.

In this seminar, I will present the results of my PhD, defended last September. I will first outline the scientific context and the experimental setup, before providing an overview of the analysis procedure and discussing the interpretation of the data in light of theoretical predictions. The results will then be placed within the framework of multi-messenger investigations and compared with previous results obtained using other probes. Finally, I will discuss the prospects offered by the neutron probe and the ongoing efforts to further elucidate the nature of the PDR.

In recent years, energy-flow (light-ray) operators have emerged as a common language linking theory and experiment for mapping the dynamics of quantum field theories.

In this talk, I will survey how multi-point energy correlators are used to characterize QCD matter in high-energy scattering, with emphasis on heavy ion collisions. I will review the theoretical status of light-ray correlation functions—including factorization, evolution, and medium-induced modifications—and summarize the corresponding experimental measurements. I will then argue that these observables provide controlled access to (non-vacuum) non-trivial quantum states, offering a bridge between collider phenomenology and formal developments in quantum field theory where such states remain poorly understood.

The seminar will be streamed via Zoom (link)