III Russian-Spanish Congress

8 Sept 2015, 07:00 → 11 Sept 2015, 18:00 Europe/Zurich

Santiago de Compostela

A joint meeting among leading Russian and Spanish Scientists will take place in Santiago de Compostela, September 8th-11th. The purpose of the meeting is to strengthen the already existing collaborations and initiate new ones. The organization expects to cover living expenses of around 10-15 russian scientists. The deadline for applications is 15 May-2015. The conference fee is 130 euros. Russian scientists are exempt. The organization will cover the hotel and living expenses of a limited number of russian participants.

Tuesday 8 September

1 Reception

Session 1

Convener: Mikhail Braun

2 Welcome

Speaker: Carlos Pajares Vales (Universidade de Santiago de Compostela (ES))

3 Low-energy signals of dynamical electroweak symmetry breaking

Strongly-coupled electroweak scenarios are characterized by a spectrum of massive states at high scales. Using effective field theory techniques, we analyse their phenomenological implications at low energies. Integrating out the heavy particles, one gets a definite pattern of low-energy couplings in the resulting effective Lagrangian, which depends on the quantum numbers associated with the integrated states and the ultraviolet properties of the underlying dynamics. A systematic study of these patterns will help to infer useful dynamical information from any future experimental signals indicating small deviations from the Standard Model predictions.

Speaker: Antonio Pich (University of Valencia)

4 The case of a strongly interacting electroweak symmetry breaking sector at the LHC

The current data concerning the Higgs discovered at the LHC are compatible with having a strongly interacting electroweak symmetry breaking dynamics for the Higgs and the would-be Goldstone bosons. In this work we review this possibility and the consequences for LHC II.

Speaker: Antonio Dobado (Universidad Complutense (ES))

5 Running vacuum energy in the expanding Universe: from inflation to our dark energy era

An accelerated universe should naturally have a vacuum energy density determined by its dynamical curvature. The so-called cosmological constant is most likely a temporary description of a cosmic variable that has been drastically evolving from the early inflationary era to the present. In this talk, I will discuss a unified picture (in fact a class of models) of the expansion history of our Universe implementing such an idea. The main stages, from inflation and its (``graceful'') exit into a standard radiation regime, as well as the matter and dark energy epochs, are accounted for. Furthermore, for a generic Grand Unified Theory associated to the inflationary phase, the amount of entropy generated from primeval vacuum decay within this class of models can explain the huge value measured today.

Speaker: Prof. Joan Solà (Universitat de Barcelona)

6 Cosmological perturbations of the Higgs vev

The standard Higgs mechanism for electroweak symmetry breaking predicts, apart from the existence of a scalar boson, the presence of a constant vacuum expectation value of the Higgs field. The Higgs vev, being determined by the effective potential, can however acquire space-time fluctuations from loop effects in inhomogeneous metric backgrounds. In this talk, we will present recent results on the determination of the finite part of the one-loop effective potential in perturbed Robertson-Walker backgrounds which has been obtained by means of dimensional regularization techniques. Potential astrophysical or cosmological signatures will be also discussed.

Speaker: Antonio Lopez Maroto

11:15 Break

Session 2

Convener: Dmitri Kazakov (JINR/ITEP)

7 Axion-Higgs interplay in the two Higgs-doublet model

We study the Dine-Fischler-Srednicki (DFS) model in the light of the recent Higgs LHC results and electroweak precision data. The DFS model is a natural extension of the two-Higgs doublet model endowed with a Peccei-Quinn symmetry and leading to a physically acceptable axion. For generic couplings, the model reproduces the minimal Standard Model showing only tiny deviations (extreme decoupling scenario) whereas all additional degrees of freedom (with the exception of the axion) are very heavy. Recently, new corners of this model have been highlighted where it may exhibit enlarged global symmetries making the corresponding models technically natural (naturalness scenario). In some cases an additional Higgs could be present at the weak scale. In this case, the new light 0+ state would be accompanied by relatively light charged and neutral pseudoscalar Higgses. We will use the oblique corrections, particularly Δρ, to constrain the mass spectrum in this case. As a final result, we also work out the non-linear parametrization of the DFS model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale

Speaker: Domenec Espriu Climent (University of Barcelona (ES))

8 Bottom-up holographic approach to QCD

One of the most known result of the string theory consists in the idea that some strongly coupled gauge theories may have a dual description in terms of a higher dimensional weakly coupled gravitational theory --- the so-called AdS/CFT correspondence or gauge/gravity correspondence. The attempts to apply this idea to the real QCD are often referred to as "holographic QCD" or "AdS/QCD approach". One of directions in this field is to start from the real QCD and guess a tentative dual higher dimensional weakly coupled field model following the principles of gauge/gravity correspondence. The ensuing phenomenology can be then developed and compared with experimental data and with various theoretical results. Such a bottom-up holographic approach turned out to be unexpectedly successful in many cases. In the given talk, we make a short review of the bottom-up holographic approach to QCD and some of its applications.

Speaker: Sergey Afonin (Saint Petersburg State University)

9 Cold holographic matter

After a brief review of the Landau Fermi liquid theory, we will discuss a holographic modeling of cold matter in terms of D-brane intersections. We will analyze the different regimes of these systems as a function of the temperature and, in particular, their zero-sound and diffusion modes.

Speaker: Prof. Alfonso Ramallo (University of Santiago de Compostela)

13:00 Lunch

Session 3

Convener: Antonio Dobado

10 Topological entropy, holography and renormalization group flows

We will review the latest developments on global properties of the renormalization group flow in different space-time dimensions (c-theorem, a-theorem and F-theorem). In particular, we will address the case of odd dimensions where new entropic conjectures have been recently formulated.

Speaker: Prof. Manuel Asorey (Universidad de Zaragoza)

11 Recent developments in Skyrme models: theory and applications

The foundations of new Skyrme models with integrability and BPS properties, are presented. Their main applications for hadrons, nuclei and nuclear matter are briefly reviewed. A new field theortical thermodinamics and a geometric theory of matter are thereby established and explained.

Speaker: Prof. Joaquin SANCHEZ-GUILLEN (USC)

12 Complete EOS of Neutron Stars described with the microscopically based Barcelona-Catania-Paris-Madrid Energy Density Functional

To be announced.

Speaker: Prof. Xavier Viñas (University of Barcelona)

16:00 Break

Session 4

Convener: Domenec Espriu Climent (University of Barcelona (ES))

13 BPS Skyrme model and neutron stars, a two-fold approach

The Skyrme model was conceived as a low energy effective field theory of strong interactions where the fundamental degrees of freedom are the pions and nuclei appear as collective excitations. In this talk, we will focus on a special case of these Skyrme theories called BPS Skyrme Model, which allows for a good description of binding energies of high nuclei. Further, here we will present two different approaches to the study of neutron stars. On the one hand, a full theory description with the gravity back-reaction taken into account. On the other hand, a mean-field approach allowing to the usual TOV calculations. Other interesting new results will be presented.

Speaker: Mr Carlos Naya (USC)

14 Modeling of interaction of quantum fields with extended object in the framework of Symanzik approach

The results obtained in the models of interaction 2-dimensional material objects with QED fields, constructed on the basis of Symanzik approach are presented. The possibility of applications of such methods for modeling the interaction of photons and electrons with hadrons and nuclei is discussed.

Speaker: Prof. Yuri Pismak (Saint-Petersburg State University)

15 Perturbation analysis in no local cosmological models

Speaker: Sergey Vernov (Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow Stat)

16 Heavy Quark Spin Symmetry and the partners of the $X(3872)$

The discovery of the $X(3872)$ by the Belle collaboration [1] and its confirmation by BaBar and CDF has provided the best candidate to an exotic structure in the meson sector. Because of its proximity to the $D^*D$ threshold a description of this state in terms of a $c\bar c$ state coupled to a $D^*D$ molecular structure seems to be natural. For the heavy quark sector, the spin-dependent interactions are of the order $1/m_Q$ and vanish in the heavy quark limit $m_Q\rightarrow \infty$. Then the dynamics involving heavy quarks are independent of their spin leading to heavy quark spin symmetry (HQSS). This symmetry has been often used to constrain effective hadronic models. Recently the LHCb Collaboration has determined unambiguously the $X(3872)$ quantum numbers to be $J^{PC}=1^{++}$. Based on this result HQSS suggest the existence of $X(3872)$ partners either in the $c\bar c$ sector with $J^{PC}=2^{++}$ or in the $b\bar b$ sector with $J^{PC}=1^{++}$ or $2^{++}$. An extensive experimental search has been done by LHCb for the $J^{PC}=1^{++}$ bottom partner of the $X(3872)$, the so-called $X_b$ through its decay to different channels, but no evidence of an $X_b$ signal has been observed. In this work we perform a calculation of the possible partners of the $X(3872)$ using a constituent quark model which has been successful in describing the hadronic phenomenology [2]. In this framework the $X(3872)$ resonance is understood as a mixture of a P-wave charmonium $\chi_{c1}(2P)$ and a S-wave $DD^*$ molecule. The $D-D^*$ residual interaction, driven basically by one pion exchange, is not enough attractive to form a $DD^*$ bound state but the coupling with the $c\bar c$ state, slightly above the $DD^*$ threshold produces the attraction necessary to bind the system. This is not the case of the $J^{PC}=2^{++}$ $D^*D^*$ molecule where the absence of a $c\bar c$ state nearby avoid the formation of a bound states. In the bottom sector the situation is different. In this case, as the bottom quark mass is larger than the charm quark mass, the interaction in the $BB^*$ and the $B^*B^*$ systems is enough attractive to produce loosely bound states. However in the $BB^*$ $J^{PC}=1^{++}$ case a $b\bar b$ state exists just below threshold. The coupling with this states produces repulsion and the $BB^*$ bound state disappears. In the $B^*B^*$ system any nearby $b\bar b$ state does exit and the $J^{PC}=2^{++}$ remains as a bound state with a mass of 10650 MeV.$/c^2$ Therefore, although HQSS predicts more bound states the coupled channels dynamics breaks the symmetry and only the $B^*B^*$ $J^{PC}=2^{++}$ state survives. Similar effects are analyzed in the heavy baryon sector. \vspace{12pt} [1] S. K. Choi $\it et al$ (Belle Collaboration) Phys. Rev. L $\bf 91$ 262001 (2003). [2] J. Vijande, F. Fern\'andez, and A. Valcarce, J. Phys. G {\bf 31}, 481 (2005). J. Segovia, A. M. Yasser, D. R Entem and F. Fern\'andez, Phys. Rev. D {\bf 78} 114033 (2008).

Speaker: Prof. Francisco Fernandez (Universidad de Salamanca)

Wednesday 9 September

Session 5

Convener: Antonio Pich (University of Valencia)

17 New method of quantization of the Yang-Mills theory

A new method of quantization of the nonabelian gauge theories is reviewed

Speaker: Andrey Slavnov (Steklov Mathematical Institute and Moscow State University)

18 Summation of UV divergences in maximally supersymmetric Yang-Mills theories in diverse dimensions

We consider the UV divergences in scattering amplitudes in maximally supersymmetric Yang-Mills theories in diverse dimensions: (D=6, N=2), (D=8, N=1) and (D=10, N=1) cases. The recurrence relation is found that allows one to get the leading divergences in all orders of PT for the four point amplitude. It is checked by explicit calculations in several loops. Infinite summation of the leading divergences leads to finite results in the limit when regularization is removed. We discuss the meaning of this observation which might have the far reaching consequences.

Speaker: Prof. Dmitry Kazakov (JINR)

19 Zero modes, heat kernel expansions, spectral zeta functions. A novel approach.

Many phenomena in statistical physics and quantum field theory are effectively described by means of spectral zeta function techniques. In particular, one-loop quantum fluctuations around classical backgrounds engender divergences that may be regularized via spectral zeta function analytic continuation regularization. Tipically, in solitonic and/or gravitational backgrounds, e.g., magnetic monopoles, domain walls, black holes, there are zero energy fluctuation modes. These zero modes cause infrared divergences in the low temperature or long proper imaginary time asymptotics of the heat kernel expansion. The heat kernel expansion is a necessary ontermediate tool to obtain the zeta function through Mellin's transform. In this talk I wll describe a new method to deal with the infrared regime of the fluctuation spectrum by performing the expansion with respect to an operator with an algebraic kernel of the same dimension as the Hessian operator. In absence of zero modes the heat kernel expansion starts from the heat kernel of the usual Laplace operator. The new technique will be applied to control the infrared divergent fluctuations around instantons in quantum mechanics, kinks in one-dimensional QFT, two-dimensional self-dual vortices in superconducting systems, and domain walls in scalar 3D QFT.

Speaker: Dr Mateos Guilarte Juan (Universidad de Salamanca)

20 Renormalization-group improved inflationary scalar electrodynamics and SU(5) scenarios

The possibility to construct inflationary models for the renormalization-group (RG) improved potentials corresponding to scalar electrodynamics and to SU(2) and SU(5) models is investigated. In all cases, the tree-level potential, which corresponds to the cosmological constant in the Einstein frame, is seen to be nonsuitable for inflation. Rather than adding the Hilbert-Einstein term to the action, quantum corrections to the potential, coming from the RG equation, are included. The inflationary scenario is analyzed with unstable de Sitter solutions that correspond to positive values of the coupling function, only. We show that, for the finite SU(2) model and SU(2) gauge model, there are no de Sitter solutions suitable for inflation, unless exit from it occurs according to some weird, nonstandard scenarios. Inflation is realized both for scalar electrodynamics and for SU(5) RG-improved potentials, and the corresponding values of the coupling function are seen to be positive. It is shown that, for quite reasonable values of the parameters, the inflationary models obtained both from scalar electrodynamics and from the SU(5) RG-improved potentials are in good agreement with the most recent observational data. Report is based on E. Elizalde, S. D. Odintsov, E. O. Pozdeeva and S. Yu. Vernov, PHYSICAL REVIEW D 90, 084001 (2014)

Speaker: Ekaterina Pozdeeva (SINP MSU)

21 Nonlocal gravity from generalised spacetime structure

There are two basic ways of modifying gravity: considering either more general theories for the metric or allowing spacetime degrees of freedom besides the metric. Here the aim is to find possible relations between gravitational theories obtained within these two seemingly distinct approaches. In the framework of the so called C-theories the spacetime connection has a prescribed relation to the curvature of the spacetime, generalising the usual Palatini theories. On the other hand, they can be related to non-local metric models. This hints at a novel geometrical interpretation of a nonlocal structure as an emergent property of non-Riemannian spacetime structure.

Speaker: Alexey Golovnev

11:00 Break

Session 6

Convener: Lev Lipatov (P)

22 Signatures of parity violations in heavy ion collisions

Speaker: Vladimir Andrianov (University of St Petesburg)

23 PT symmetric classical and quantum cosmology

According to modern observational data the phantom equation of state for dark energy is not excluded. This scenario creates problems with stability of universe evolution. An alternative to phantom models is given by models of scalar matter with non-Hermitian, PTsymmetric interaction[1]. In this talk we present the set of such models with several scalar fields which are exactly (analytically) solvable both in classical and in quantum case[2]. The latter case is investigated in the Friedmann-Robertson-Walker minisuperspace approach. We use advantages of analytical solvability to disentangle the differences between phantom and PT symmetric dynamics and give arguments in favor to the latter one. References [1] A. A. Andrianov, F. Cannata, A. Y. Kamenshchik and D. Regoli, Phan- tom cosmology based on PT symmetry, Int. J. Mod. Phys. D, 19 (2010), 97–111. [2] A. A. Andrianov, O. O. Novikov, Chen Lan. Quantum cosmology of the multi-eld scalar matter: some exact solutions, arXiv:1503.05527v1 (2015), 1-16.

Speaker: Alexander Andrianov (Saint Petersburg State University)

24 Aspects of integrable deformations of strings in symmetric spaces and AdS(5)xS(5)

I will summarize recent work aimed to show that sigma models on (semi-)symmetric spaces F/G admit discrete integrable deformations that can be viewed as deformations of the F/F gauged WZW model. For the AdS(5)xS(5) world-sheet theory, F=PSU(2,2|4) and the resulting theory has just the right amount of kappa-symmetries, which points to the existence of a new fully consistent deformed string background.

Speaker: Prof. J. Luis Miramontes (Universidade de Santiago de Compostela)

25 Exact thick brane solutions in the model with several scalar fields

The model of scalar matter that permits the formation of a domain wall (thick brane) is studied. The potential of the scalar matter is assumed to have $O(N)$ symmetry softly broken by terms quadratic in fields. One of the fields develops delocalized kink background while others may or may not form localized configurations depending on the relative values of the parameters. We present exact background solutions for arbitrary number of fields and discuss possible applications for model building based on the idea of large extra dimensions.

Speaker: Oleg Novikov (Saint-Petersburg State University, V.A.Fock Department of Theoretical Physics)

26 Cosmological Higgs-Axion interplay for a naturally small electroweak scale

Recently, a new mechanism to generate a naturally small electroweak scale has been proposed. It exploits the coupling of the Higgs to an axion-like field and a long era in the early universe where the axion unchains a dynamical screening of the Higgs mass. We present a new realization of this idea with the new feature that it leaves no signs of new physics up to a rather large scale, 10^9 GeV, except for two very light and weakly coupled axion-like states. One of the scalars can be a viable Dark Matter candidate. Such a cosmological Higgs-axion interplay could be tested with a number of experimental strategies.

Speaker: Oriol Pujolas Boix

13:10 Lunch

Excursion: A Toxa island and San Vicente do Mar

Thursday 10 September

Session 7

Convener: Carlos Albert Salgado Lopez (Universidade de Santiago de Compostela (ES))

27 Euler-Lagrange equations for the high energy effective actions in QCD and gravity

The theory of high energy processes in QCD is based on the gluon reggeization. In particular, Pomeron and Odderon are composite states of two and three reggeized gluons, respectively. We discuss the effective action and corresponding classical equations for quarks and gluons interacting with reggeized gluons. In the extended N=4 supersymmetric gauge model the Pomeron is dual to the reggeized graviton living on the anti-de-Sitter 10-dimensiona space. Therefore to construct the Gribov Pomeron calculus in this model one should calculate the Regge trajectory and various vertices for reggeized gravitons. We formulate the effective action describing the reggeized graviton interactions and derive the Euler-Lagrange equation for this action.

Speaker: Prof. Lev Lipatov (Petersburg Nuclear Physics Institute)

28 Particle Production in Hybrid Formalism at NLO

We reconsider the perturbative next-to-leading calculation of the single inclusive hadron production in the framework of the hybrid formalism, applied to hadron production in proton-nucleus collisions. We introduce the explicit requirement that fast fluctuations in the projectile wave function which only exists for a short time are not resolved by the target.This Ioffe time cutoff also strongly affects the next-to-leading order terms. Our final expressions are unambiguous and do not coincide at next-to-leading order with the results available in the literature.

Speaker: Tolga Altinoluk

29 Search for BFKL-effects at high energies

To be announced.

Speaker: Victor Kim (Petersburg Nuclear Physics Institute)

30 Collisions of two projectiles on two targets in the BFKL approach

High-energy collisions of two nucleons on two nucleons are studied in the BFKL approach in the leading approximation in $\alpha_sN_c$. Total cross-section as well as single and double inclusive cross-sections for gluon production are considered. Diagrams both with and without redistribution of colour are taken into account. It is found that intermediate BKP states consisting of 4 reggeized gluons give a contribution which may be observable in deuteron-deuteron scattering.

Speaker: Prof. Mikhail Braun (Department of High Energy Physics, Saint-Petersburg State University, S. Petersburg, Russia)

11:00 Break

Session 8

Convener: Irina Aref'eva (Steklov mathematical Institute)

31 Repulsion of quark-gluon strings and collective effects in two-particle angular long-range correlations in hadronic collisions

\documentclass[]{article} \begin{document} \title{ Repulsion of quark-gluon strings and collective effects in two-particle angular long-range correlations in hadronic collisions } \author{ I.G.Altsybeev, G.A.Feofilov\\ {\it \small Saint-Petersburg State University}\\ } \date{}%draft v0.2} \maketitle Color flux tubes (quark-gluon strings), formed at early stages of hadron-hadron collision, may overlap in case of sufficiently high densities and interact by repelling or attracting each other \cite{1}. In the hypothesis of repulsive interaction, strings may acquire, before the hadronization, the additional transverse boost that is an efficient sum of all accounted string-string interactions. This produces additional transverse momenta to the particles formed in string decays over a wide range of rapidity, thus leading to modification of observables and to azimuthal asymmetry of two-particle correlations. Monte Carlo toy-model \cite{2,3} with the account of the string repulsion is implemented, where an efficient string-string interaction radius is introduced. We consider this string repulsion as the main dynamic origin of the elliptic flow and of the higher harmonics that describe the complicated structures observed in two-particle correlation topology in nucleus-nucleus collisions at RHIC and at LHC. The approach is also discussed for the high-multiplicity proton-proton and proton-nucleus high-energy collisions. {\it Acknowledgements.} This work is supported by the Saint-Petersburg State University research grant 11.38.242.2015. \begin{thebibliography}{99} \bibitem{1} V.A. Abramovsky, O.V. Kanchely, JETP letters 31, 566(1980); Abramovskii V. A., Gedalin E. V., Gurvich E. G., Kancheli O. V., JETP Lett., vol.47, 337-339 (1988). \bibitem{2} G.Feofilov, I.Altsybeev, O.Kochebina, PoS (Baldin ISHEPP XXII) 067 (2015). \bibitem{3} I. Altsybeev, proceedings of the XI Quark Confinement and the Hadron Spectrum Conference, arXiv:1502.03608 [hep-ph] (2015). \end{thebibliography} \end{document}

Speaker: Dr Grigori Feofilov (Saint-Petersburg State University)

32 Universal geometrical scaling of elliptic flow

Speaker: Carlos Pajares Vales (Universidade de Santiago de Compostela (ES))

33 Forward-Backward Correlation between Mean Event Transverse Momenta in String Fusion Model

The explicit analytical expression for the asymptotic of the correlation coefficient between mean event transverse momenta of charged particles produced in separated rapidity intervals is derived. The asymptotic at large string density is obtained in the model with string fusion by introducing a lattice in the transverse plane and assuming the translational invariance of the particle production from strings in rapidity at high energies. It is found that in contrast to the correlation between transverse momenta of single particles the strength of the correlation between mean event transverse momenta in two separated rapidity intervals is not decrease with the total number of initial strings. That makes this type of correlation promising for the observation in relativistic heavy ion collisions. It is also found that in this limit the strength of the correlation does not depends on the variance in the number of particles produced by a single sources, in contrast to the correlation between multiplicities or the transverse momentum and multiplicity. The work was supported by the RFBR grant 15-02-02097-a and the Saint-Petersburg State University grant 11.38.197.2014.

Speaker: Vladimir Vechernin (Saint-Petersburg State University)

vechernin-IIIRSC.pdf

34 Forward-backward multiplicity correlations in pp collisions with the ALICE detector

I. Altsybeev for the ALICE Collaboration. The strength of forward-backward (FB) multiplicity correlations is measured by the ALICE detector in proton-proton collisions at $\sqrt{s}=0.9$, 2.76 and 7 TeV. Such correlations are considered to be a powerful tool for the exploration of the initial conditions of hadronic interactions. The measurement is performed in the central pseudorapidity region ($|\eta| < 0.8$) for the charged tracks with transverse momentum $p_{\rm{T}}>0.3$ GeV/$c$. Two separate pseudorapidity windows of width ranging from 0.2 to 0.8 are chosen symmetrically around $\eta=0$. The multiplicity correlation strength ($b_{\rm corr}$) is found to decrease with increasing pseudorapidity gap and shows a non-linear increase with the width of these windows. A sizable increase of the correlation strength with the collision energy is observed. The correlation coefficient is also measured for multiplicities in different configurations of two azimuthal sectors selected within the symmetric FB $\eta$-windows. Two different contributions, short-range (SR) and long-range (LR), are observed. The energy dependence of $b_{\rm corr}$ is found to be weak for the SR component while it is strong for the LR component. Moreover, the correlation coefficient is studied for particles belonging to various transverse momentum intervals chosen to have the same mean multiplicity. Both SR and LR contributions to $b_{\rm corr}$ are found to increase with $p_{\rm{T}}$ in this case. Results are compared to PYTHIA and PHOJET event generators and to a string-based phenomenological model. The observed dependencies of $b_{\rm corr}$ add new constraints on phenomenological models.

Speaker: Igor Altsybeev (St. Petersburg State University (RU))

FB_correlations_in_pp_Rus-Spanish_Congress_2015_v1.2.pdf

35 Strongly intensive fluctuations in nucleus-nucleus collisions at high energy in Monte Carlo model with string fusion

The exploration of the QCD phase diagram and a search for the critical point is one of the main subjects of heavy ion physics. The experimental investigation of the phase diagram of a strongly interacting matter is related to the study of the fluctuations and correlations of observables in the nuclear collisions at high energy. Around the critical point, enhanced fluctuations are expected to appear. Such behavior related to strong fluctuations in colors of strings could be expected in the framework of the string fusion approach [1,2], where around percolation threshold, when the processes of string fusion and percolation come into play, the critical behavior takes place. The large extent of string overlap can be considered as a possible way of quark-gluon plasma formation. As it was shown [3], the equation of state of the QGP at zero chemical potential, obtained in the color string percolation model, is in an excellent agreement with the lattice results. In the present work, the string-parton Monte Carlo model [4] is applied to heavy and light ion collisions at the center of mass energy range from a few up to several hundred GeV per nucleon. The implementing of both the string fusion and the finite rapidity length of strings allowed considering the particle production at non-zero baryon density. In addition to long-range correlation studies [5], we calculated several types of strongly intensive event-by-event variables [6] as a function of rapidity and collision energy and provided predictions for the experiment. The author acknowledges Saint-Petersburg State University for the research grant 11.38.193.2014 and Special Rector’s Scholarship. He is also grateful to the Dynasty Foundation. [1] N.S. Amelin, N. Armesto, M.A. Braun, E.G. Ferreiro, C. Pajares, Phys. Rev. Lett. 73, 2813 (1994). [2] M.A. Braun, F. del Moral, C. Pajares. Eur. Phys. J. C 21, 557 (2001). [3] R. P. Scharenberg, B. K. Srivastava, A. S. Hirsch, Eur. Phys. J. C 71, 1510 (2011); B. K. Srivastava, Nucl. Phys. A 926, 142 (2014). [4] V. N. Kovalenko, Phys. Atom. Nucl. 76, 1189 (2013); V. Kovalenko, V. Vechernin, PoS (Baldin ISHEPP XXI) 077 (2012). [5] V. Kovalenko, V. Vechernin, PoS (Baldin ISHEPP XXII) 069 (2015). [6] M. I. Gorenstein and K. Grebieszkow, Phys. Rev. C 89, 034903 (2014); M. Gazdzicki, M. I. Gorenstein and M. Mackowiak-Pawlowska, Phys. Rev. C 88, 024907 (2013).

Speaker: Vladimir Kovalenko (St. Petersburg State University (RU))

Kovalenko_Spain4.pdf

13:00 Lunch

Session 9

Convener: Nestor Armesto Perez (Universidade de Santiago de Compostela (ES))

36 The symmetries of Carroll (super) particle

We investigate particles whose dynamics are invariant under the (AdS) Carroll group. Although a single free (Ads) Carroll particle.has non-trivial dynamics, there is non-trivial dynamics when there is a coupling to background Carroll gauge fields or when we consider two particles. The extension to the supersymmetric case will be considered. The construction of a Carroll string will be also studied.

Speaker: Joaquim Gomis (Universitat de Barcelona)

37 The lightest scalar meson and its non-ordinary nature.

In this talk I will review the present status of the lightest scalar meson resonance, which has been a controversial state for many decades despite playing a central role in our understanding of the QCD spontaneous symmetry breaking and the nucleon-nucleon attraction. Recently, the debate about its existence and parameters has been finally settled. In addition, there are strong indications that this is not an ordinary quark-antiquark state, coming form large Nc, Regge Theory, and many other approaches, including lattice.

Speaker: Jose R. Pelaez (Universidad COmplutense)

38 Medium-induced two gluon radiation

Multiple gluon emissions of a high energetic parton passing through a hot and dense QCD medium are usually assumed to be independent and given by iterating the well-studied single inclusive gluon emission. However, it is known that interferences among different emitters in the parton cascades are known to lead to angular ordering of gluon emissions in the vacuum. Motivated by this, we consider the two gluon emission spectrum at leading order in a dense medium using semi-classical eikonal formalism. We compute the leading order probability to emit two gluons by such a highly energetic parton in a dense QCD medium. An analytical expression for the two gluon spectrum is obtained in terms of the in-medium n-point correlation functions, that we evaluate more explicity in the large N_C limit. Our results can also reproduce the well known picture of the vacuum case

Speaker: Mr Manoel Rodríguez Calvo (Universidade de Santiago de Compostela)

16:00 Break

Session 10

Convener: Valery Rubakov (Inst. for Nucelar Resarch, RAS, Moscow)

39 p-Pb collisions at the LHC and nPDFs

To be announced.

Speaker: Dr Pia Zurita (Universidade de Santiago de Compostela)

40 Meson gas properties and chiral symmetry restoration

I will discuss recent progress in low-energy QCD at finite temperature regarding chiral symmetry restoration and properties of meson gases relevant for Heavy-Ion Physics and lattice simulations. In particular, I will present a recent analysis of scalar and pseudo-scalar susceptibilities $\chi_S$ and $\chi_P^a$, which allows to understand chiral partner degeneration at chiral symmetry restoration in a consistent framework built from model-independent assumptions. On the one hand, correlator identities confirmed by Chiral Perturbation Theory allow to relate $\chi_P^a$ and quark condensates for different channels in the light and strange sectors. On the other hand, such identities and the $O(4)$ $S/P$ degeneration pattern are supported by direct analysis of lattice data for screening masses, quark condensates and scalar susceptibilities. The role played by the thermal $f_0(500)$ will be particularly emphasized. In fact, saturation of $\chi_S$ by the $f_0(500)$ state dynamically generated through thermal unitarization within ChPT, gives rise to a peak compatible with the lattice transition point, consistent with partner degeneration. I will also discuss resummation schemes such as large-$N_f$ in which properties such as thermal unitarity and the thermal $f0(500)$ pole behaviour hold exactly. Some recent progress on chiral symmetry properties in the presence of external magnetic fields could also be discussed.

Speaker: Angel Gomez Nicola (Universidad Complutense Madrid)

41 The impact of e+A collisions on nuclear PDFs

e+A collisions can bring useful information to questions that A+A cannot (fully) answer. In particular, they can shed light on the distribution of partons within nuclei. This is most relevant in the case of the gluon, which suffers from huge uncertainties in the small-x regime. We show how to implement data from e+A collisions into existing nPDFs and the impact these collisions have on said distributions.

Speaker: Manoel R. Moldes

Session in memory of K. Gridnev

42 Introduction

Speaker: Xavier Viñas (Universidad de Barcelona)

43 Gridnev

Speaker: Dmitry Gridnev (Saint Petersburg State University)

21:00 Conference dinner

Friday 11 September

Session 11

Convener: Enrique Zas (Universidade de Santiago de Compostela)

44 Baryon Acoustic Oscillations and the Expansion History of the Universe

The tiny inhomogeneities left over from the inflationary phase seeded the early Universe with primordial density perturbations. The photon-baryon fluid reacted to these perturbations by forming spherical pressure waves known as baryon acoustic oscillations (BAO). These waves propagated through the primordial plasma until the Universe became transparent to radiation, effectively stopping the dragging of the baryons by the photons. This left the Universe with a matter overdensity at a fixed scale (the sound horizon: 480 million light years) which was later imprinted in the galaxy distribution. This characteristic scale has been used for the past 10 years as a "standard ruler" to constrain the relation between the distance to astrophysical objects and the redshift of their photons due to the Universe's expansion. This is known as the distance-redshift relation, which encodes the expansion history of the Universe. Modern galaxy surveys such as the Baryon Oscillation Spectroscopic Survey (BOSS) are playing a key role in determining this relation with high precision, allowing us to place strong constraints on the recent phase of accelerated expansion of the Universe and therefore on dark energy. I will describe the current state of the art of BAO measurements and discuss their implications on the standard cosmological model.

Speaker: Mr Antonio J. Cuesta (Institut de Ciències del Cosmos - Universitat de Barcelona)

45 Ultrahigh energy neutrinos at the Pierre Auger Observatory

The observation of ultrahigh energy neutrinos has become a priority in experimental Astroparticle Physics. They can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere or in the Earth's crust, producing air showers that can be observed with arrays of detectors at the ground. With the Surface Detector of the Pierre Auger Observatory we are sensitive to neutrinos in the sub-EeV energy range and above. A search for UHE neutrinos has yielded no candidates and a limit to the diffuse flux of ultrahigh energy neutrinos has been placed that challenges the Waxman-Bahcall bound predictions, and constrains their production in interactions of ultrahigh energy cosmic rays with the Cosmic Microwave Background radiation.

Speaker: Jaime Alvarez-Muniz (Universidad de Santiago de Compostela)

46 The high energy neutrino events at IceCube

IceCube has published the observation of 37 events of TeV-PeV energies. We show that the angular distribution, the spectrum and the muon to shower ratio of these events can not be explained by atmospheric neutrinos. On the other hand, IceCube's interpretation in terms of a diffuse astrophysical flux with $E^{-2}$ spectrum implies events at the Glashow resonance (6.4 PeV) that have not been observed yet. We obtain an excellent fit if cosmogenic neutrinos of ultrahigh energy experience new neutral current interactions that are very soft, with only a small fraction of energy being transferred to the target nucleon. We discuss models that may provide cross sections with the precise features required to fit the data.

Speaker: Manuel Masip (Universidad de Granada)

47 Quantum Vacuum and Cosmology with a Background of Zeta Functions

What drives the acceleration of the Universe expansion? Dark energy, of course, but what is it? Beautiful mathematics, involving the zeta function of pseudodifferential operators, are key in answering this question. After summarizing the uses of the zeta function for the definition of regularized traces and determinants, the motivations behind the celebrated Chowla-Selberg formula will be discussed, together with some non-trivial generalizations of it and some applications in Physics and Cosmology.

Speaker: Prof. Emilio Elizalde (ICE-CSIC and IEEC, Barcelona)

48 Global holographic effects

Speaker: Irina Aref'eva (Steklov mathematical Institute)

49 Conformal Universe as false vacuum decay holofraphic picture

Speaker: Valery Rubakov (Ins. for Nuclear Research, Ras, Moscow)

11:10 Break

Session 12

Convener: Vladimir Andrianov (Saint Petersburg State University)

50 The Pierre Auger Observatory: latest results and future prospects for Astroparticle and Particle Physics

We highlight the main results obtained by the Pierre Auger Collaboration in its quest to unveil the mysteries associated with the nature and origin of the highest-energy cosmic rays. The observatory has steadily produced high-quality data for more than 10 years, which have already led to a number of major breakthroughs in the field contributing to the advance of our understanding of these extremely energetic particles. The interpretation of our measurements so far opens new questions which will be addressed by the foreseen upgrade of the Pierre Auger Observatory.

Speaker: Ines Valino (University of Santiago de Compostela)

51 Effects of pseudoscalar condensate on the rate of cooling of neutron stars.

We consider the effect that the appearance of pseudoscalar condensates in a neutron star can have on its cooling rate. We make no particular assumption on the origin and characteristics of these possible condensates and only assume that in regions where the pseudoscalar density varies the propagation of photons is governed by modified Maxwell-Chern-Simons electrodynamics. We find that this gives non-trivial reflection coefficients between regions of different pseudoscalar density and may affect the star cooling rate.

Speaker: Sergey Kolevatov (SPbSU)

52 Progress in the determination of details of inflaction

Speaker: Alexei Starobinsky (Landau Inst. of Theoretical Physics, RAS, Moscow)