Espriu, D. (Domènec)
Overview
Works:  30 works in 57 publications in 3 languages and 197 library holdings 

Genres:  Conference papers and proceedings 
Roles:  Editor, Other, Author, Contributor 
Classifications:  QC794.8.E44, 539.744 
Publication Timeline
.
Most widely held works by
D Espriu
Advanced School on Electroweak Theory : Maó, Menorca, Spain, 1622 June 1996 by
D Espriu(
Book
)
9 editions published between 1998 and 2014 in English and held by 96 WorldCat member libraries worldwide
9 editions published between 1998 and 2014 in English and held by 96 WorldCat member libraries worldwide
II RussianSpanish Congress on Particle and Nuclear Physics at all Scales, Astroparticle Physics and Cosmology : St. Petersburg,
Russia 14 October 2013 by
American Institute of Physics(
)
3 editions published in 2014 in English and held by 53 WorldCat member libraries worldwide
3 editions published in 2014 in English and held by 53 WorldCat member libraries worldwide
Spontaneous generation of geometry and its possible consequences by
Daniel Puigdomènech Bourgon(
)
3 editions published in 2012 in English and held by 3 WorldCat member libraries worldwide
Generació espontània de la gravetat i possibles conseqüències observacionals. En aquesta tesi hem desenvolupat una teoria en què la gravitació d'Einstein s'obté dinàmicament mitjançant el mecanisme de ruptura espontània de simetria d'una altra teoria més fonamental. En aquesta teoria fonamental no existeix cap noció mètrica o de geometria. Tots els graus de llibertat associats a la geometria de l'espai temps emergeixen tan sols després del trencament de la simetria. El resultat final correspon a la teoria d'EinsteinHilbert naturalment equipada amb una constant cosmològica. El fet d'obtenir aquesta constant ens porta a la seva interpretació com a una propietat intrínseca de l'espai temps en contraposició a la interpretació com a descripció efectiva tan sols vàlida a escales cosmològiques. Aprofitant el fet d'obtenir una constant cosmològica diferent de zero estudiem l'efecte que aquesta té en la propagació d'ones gravitatòries. En la seva presència les ones es propaguen en un espai temps de De Sitter i no en un espai temps pla de Minkowski. Els efectes poden, en principi, ésser mesurats en observacions en sistemes locals ("redshifts" petits). Finalment estudiem la rellevància que poden tenir aquestes modificacions, degudes a la constant cosmològica, en les ones gravitatòries que podrien ser detectades mitjançant els "pulsar timing arrays" en un futur proper. La conclusió és que la inclusió de la constant cosmològica té efectes notables que podrien significar un mètode alternatiu a la mesura del valor mateix de la constant cosmològica. De fet, aquests efectes podrien facilitar la primera detecció de les ones gravitatòries
3 editions published in 2012 in English and held by 3 WorldCat member libraries worldwide
Generació espontània de la gravetat i possibles conseqüències observacionals. En aquesta tesi hem desenvolupat una teoria en què la gravitació d'Einstein s'obté dinàmicament mitjançant el mecanisme de ruptura espontània de simetria d'una altra teoria més fonamental. En aquesta teoria fonamental no existeix cap noció mètrica o de geometria. Tots els graus de llibertat associats a la geometria de l'espai temps emergeixen tan sols després del trencament de la simetria. El resultat final correspon a la teoria d'EinsteinHilbert naturalment equipada amb una constant cosmològica. El fet d'obtenir aquesta constant ens porta a la seva interpretació com a una propietat intrínseca de l'espai temps en contraposició a la interpretació com a descripció efectiva tan sols vàlida a escales cosmològiques. Aprofitant el fet d'obtenir una constant cosmològica diferent de zero estudiem l'efecte que aquesta té en la propagació d'ones gravitatòries. En la seva presència les ones es propaguen en un espai temps de De Sitter i no en un espai temps pla de Minkowski. Els efectes poden, en principi, ésser mesurats en observacions en sistemes locals ("redshifts" petits). Finalment estudiem la rellevància que poden tenir aquestes modificacions, degudes a la constant cosmològica, en les ones gravitatòries que podrien ser detectades mitjançant els "pulsar timing arrays" en un futur proper. La conclusió és que la inclusió de la constant cosmològica té efectes notables que podrien significar un mètode alternatiu a la mesura del valor mateix de la constant cosmològica. De fet, aquests efectes podrien facilitar la primera detecció de les ones gravitatòries
Searching for P and CP odd effects in heavy ion collisions by
Xumeu Planells Noguera(
)
3 editions published in 2014 in English and held by 3 WorldCat member libraries worldwide
3 editions published in 2014 in English and held by 3 WorldCat member libraries worldwide
Algunes qüestions de renormalització a la cromodinàmica quàntica by
D Espriu(
Book
)
5 editions published between 1982 and 2019 in Catalan and held by 3 WorldCat member libraries worldwide
"Sembla obligat començar fent referència a les raons teòriques i experimentals que ens fan creure en la Cromodinàmica Quàntica com en la Teoria de Camps adient a la descripció del mon hadrònic.Per a creure en una teoria necessitem, seguint Wightman, dos requisits: ha d'estar lliure de contradiccions i ha de satisfer un rang més o menys ampli d'observacions experimentals. És en aquest sentit que hom creu en les equacions de Maxwelll, però no ho fa en l'antiga teoria quàntica anterior a la Mecànica Ondulatòria. En els dos aspectes la resposta ha d'ésser matisada.Pel que coneixem fins aquest moment QCD és una teoria lliure d'inconsistències internes, al menys a un nivell molt fonamental. És una teoria de gauge i creiem en les teories de gauge per a l'explicació de totes les interaccions convenientment definida (en un sentit ampli del terme), renormalitzable i unitària.A grans trets, el problema que ens impedeix donar una resposta conclusiva és la probable inexistència de la matriu S almenys en un sentit pertorbatiu."  TDX
5 editions published between 1982 and 2019 in Catalan and held by 3 WorldCat member libraries worldwide
"Sembla obligat començar fent referència a les raons teòriques i experimentals que ens fan creure en la Cromodinàmica Quàntica com en la Teoria de Camps adient a la descripció del mon hadrònic.Per a creure en una teoria necessitem, seguint Wightman, dos requisits: ha d'estar lliure de contradiccions i ha de satisfer un rang més o menys ampli d'observacions experimentals. És en aquest sentit que hom creu en les equacions de Maxwelll, però no ho fa en l'antiga teoria quàntica anterior a la Mecànica Ondulatòria. En els dos aspectes la resposta ha d'ésser matisada.Pel que coneixem fins aquest moment QCD és una teoria lliure d'inconsistències internes, al menys a un nivell molt fonamental. És una teoria de gauge i creiem en les teories de gauge per a l'explicació de totes les interaccions convenientment definida (en un sentit ampli del terme), renormalitzable i unitària.A grans trets, el problema que ens impedeix donar una resposta conclusiva és la probable inexistència de la matriu S almenys en un sentit pertorbatiu."  TDX
Vacuum Energy in Quantum Field Theory and Cosmology by
Adrià Gómez Valent(
Book
)
2 editions published in 2017 in English and held by 2 WorldCat member libraries worldwide
2 editions published in 2017 in English and held by 2 WorldCat member libraries worldwide
Influence of the pseudoscalar condensate gradient on the cooling regime of compact stars by
A. A Andrianov(
)
1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide
1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide
Some theoretical and experimental aspects of axion physics by Albert Renau Cerillo(
)
2 editions published between 2015 and 2016 in English and held by 2 WorldCat member libraries worldwide
In this thesis we study axions, a byproduct of the PecceiQuinn solution to the strong CP problem, which are also a viable candidate for the dark matter content of the Universe. In the first part of the thesis, we revisit the DineFischlerSrednickiZhitnisky axion model in light of the recent Higgs LHC results and electroweak precision data. This model is an extension of the twoHiggsdoublet model incorporating a PQ symmetry which leads to a physically acceptable axion. For generic values of the couplings, the model reproduces the minimal Standard Model, with a massless axion and all the other degrees of freedom at a very high scale. However, in some scenarios, the extra Higgses could be relatively light. We use the oblique corrections, in particular [Delta][rho], to constrain the mass spectrum in this case. Finally, we also work out the nonlinear parametrization of the DFSZ model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale. In the second part, we study the relevance of a cold axion background (CAB) as a responsible for the dark matter in the Universe. We examine indirect consequences of its presence through its effects on photon and cosmic ray propagation. First, we study the axionphoton system under the joint influence of two backgrounds: an external magnetic field and a CAB. Their effect consists in producing a threeway mixing of the axion with the two polarizations of the photon. We determine the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical tabletop experiments. Then, we consider the case in which no magnetic field is present. Here, circularly polarized photons are energy eigenstates, with a modified dispersion relation. This enables the emission of a photon by a charged particle, such as a cosmic ray, which is forbidden in regular QED due to energymomentum conservation. We study the energy loss of a cosmic ray due to this process and compute the energy flux of photons emitted in this way, which depends on the cosmic ray spectrum
2 editions published between 2015 and 2016 in English and held by 2 WorldCat member libraries worldwide
In this thesis we study axions, a byproduct of the PecceiQuinn solution to the strong CP problem, which are also a viable candidate for the dark matter content of the Universe. In the first part of the thesis, we revisit the DineFischlerSrednickiZhitnisky axion model in light of the recent Higgs LHC results and electroweak precision data. This model is an extension of the twoHiggsdoublet model incorporating a PQ symmetry which leads to a physically acceptable axion. For generic values of the couplings, the model reproduces the minimal Standard Model, with a massless axion and all the other degrees of freedom at a very high scale. However, in some scenarios, the extra Higgses could be relatively light. We use the oblique corrections, in particular [Delta][rho], to constrain the mass spectrum in this case. Finally, we also work out the nonlinear parametrization of the DFSZ model in the generic case where all scalars except the lightest Higgs and the axion have masses at or beyond the TeV scale. In the second part, we study the relevance of a cold axion background (CAB) as a responsible for the dark matter in the Universe. We examine indirect consequences of its presence through its effects on photon and cosmic ray propagation. First, we study the axionphoton system under the joint influence of two backgrounds: an external magnetic field and a CAB. Their effect consists in producing a threeway mixing of the axion with the two polarizations of the photon. We determine the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical tabletop experiments. Then, we consider the case in which no magnetic field is present. Here, circularly polarized photons are energy eigenstates, with a modified dispersion relation. This enables the emission of a photon by a charged particle, such as a cosmic ray, which is forbidden in regular QED due to energymomentum conservation. We study the energy loss of a cosmic ray due to this process and compute the energy flux of photons emitted in this way, which depends on the cosmic ray spectrum
Production of vector resonances at the LHC via WZscattering: a unitarized EChL analysis by R. L Delgado(
)
1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide
1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide
Stellar matter with pseudoscalar condensates by
A. A Andrianov(
)
1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide
1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide
Wave propagation in metamaterials mimicking spacetime geometry: black holes and cosmic strings by Isabel Fernández Núñez(
Book
)
2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide
In physics, it is common to find different phenomena being described by similar equations. A good analogy can make us look at a problem from a different point of view. In that way, ideas may be transferred from one field of science to another, allowing to model new phenomena after previous, wellstudied ones. In the case of the field of analogue gravity, systems that mimic certain aspects of the physics of curved spacetimes are studied. In this thesis, we are interested in the analogy between geometry and media. It has been known for several decades that light propagation in a gravitational field is formally equivalent to that in a bianisotropic medium. On the one hand, ray paths are bent due to spacetime curvature. On the other hand, spatial variations of the permittivity and permeability of a material can make light follow curved trajectories. These two phenomena can be related mathematically in the context of transformation optics, which provides the tools to determine the medium parameters necessary to mimic a certain coordinate transformation. Materials with these specific properties are not naturally occurring, therefore, the emergence of metamaterial science at the beginning of the century was needed to realize them. Metamaterials are artificial composite materials with subwavelength constitutive elements that exhibit exotic properties. They have been one of the hot topics of the past years given the variety of opportunities they offer: negative refraction, superlenses, indefinite dispersion, invisibility, among many others. In this thesis we study the analogues of two static spacetimes from the point of view of transformation optics: one with spherical symmetry and one with conical geometry. Both cases are inspired by solutions to Einstein's equations: the Schwarzschild black hole and the cosmic string, respectively. For each case, we derive the permittivity and permeability of the analogous material using Plebanski's formulation of the electromagnetic constitutive equations. We solve numerically the wave equation in the metamaterial and compare the results with analytical theories. We find that the spherically symmetric spacetime can be mimicked by either an anisotropic or isotropic medium due to its rotational symmetries. This is achieved by performing a coordinate transformation of the general metric to a conformally flat form. We obtain the medium parameters for both cases and apply the results to the case of the Schwarzschild black hole. We simulate the propagation of a Gaussian beam in the two materials and compare the numerical results with the nullgeodesics in the Schwarzschild spacetime, finding a good agreement. The cosmic string is an example of a topological defect with conical geometry. A conical space can be interpreted as flat space with a wedge removed. We make use of this transformation to study the wave equation in the cosmic string background. We apply asymptotic diffraction theories to obtain analytical models that describe wave propagation of electromagnetic or gravitational waves (in a certain gauge). We find that our expressions reproduce accurately the results of the numerical simulations in the analogous metamaterial. Moreover, with our models, we can understand the observed diffraction pattern as the interference of four characteristic waves. With this interpretation we can introduce the Fresnel observation zones, which are related to the diffraction maxima. They help localize the regions – in either space or frequency – where the wave effects are more significant. In fact, in the diffraction by a noncompact object such as the cosmic string, we find that the contribution to the field of wave effects such as interference or diffraction can be of the same order as the geometrical optics terms. Furthermore, the conical topology also appears in condensed matter systems as disclinations or wedge dislocations, therefore we expect our results to be applicable in those systems as well
2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide
In physics, it is common to find different phenomena being described by similar equations. A good analogy can make us look at a problem from a different point of view. In that way, ideas may be transferred from one field of science to another, allowing to model new phenomena after previous, wellstudied ones. In the case of the field of analogue gravity, systems that mimic certain aspects of the physics of curved spacetimes are studied. In this thesis, we are interested in the analogy between geometry and media. It has been known for several decades that light propagation in a gravitational field is formally equivalent to that in a bianisotropic medium. On the one hand, ray paths are bent due to spacetime curvature. On the other hand, spatial variations of the permittivity and permeability of a material can make light follow curved trajectories. These two phenomena can be related mathematically in the context of transformation optics, which provides the tools to determine the medium parameters necessary to mimic a certain coordinate transformation. Materials with these specific properties are not naturally occurring, therefore, the emergence of metamaterial science at the beginning of the century was needed to realize them. Metamaterials are artificial composite materials with subwavelength constitutive elements that exhibit exotic properties. They have been one of the hot topics of the past years given the variety of opportunities they offer: negative refraction, superlenses, indefinite dispersion, invisibility, among many others. In this thesis we study the analogues of two static spacetimes from the point of view of transformation optics: one with spherical symmetry and one with conical geometry. Both cases are inspired by solutions to Einstein's equations: the Schwarzschild black hole and the cosmic string, respectively. For each case, we derive the permittivity and permeability of the analogous material using Plebanski's formulation of the electromagnetic constitutive equations. We solve numerically the wave equation in the metamaterial and compare the results with analytical theories. We find that the spherically symmetric spacetime can be mimicked by either an anisotropic or isotropic medium due to its rotational symmetries. This is achieved by performing a coordinate transformation of the general metric to a conformally flat form. We obtain the medium parameters for both cases and apply the results to the case of the Schwarzschild black hole. We simulate the propagation of a Gaussian beam in the two materials and compare the numerical results with the nullgeodesics in the Schwarzschild spacetime, finding a good agreement. The cosmic string is an example of a topological defect with conical geometry. A conical space can be interpreted as flat space with a wedge removed. We make use of this transformation to study the wave equation in the cosmic string background. We apply asymptotic diffraction theories to obtain analytical models that describe wave propagation of electromagnetic or gravitational waves (in a certain gauge). We find that our expressions reproduce accurately the results of the numerical simulations in the analogous metamaterial. Moreover, with our models, we can understand the observed diffraction pattern as the interference of four characteristic waves. With this interpretation we can introduce the Fresnel observation zones, which are related to the diffraction maxima. They help localize the regions – in either space or frequency – where the wave effects are more significant. In fact, in the diffraction by a noncompact object such as the cosmic string, we find that the contribution to the field of wave effects such as interference or diffraction can be of the same order as the geometrical optics terms. Furthermore, the conical topology also appears in condensed matter systems as disclinations or wedge dislocations, therefore we expect our results to be applicable in those systems as well
Numerical Relativity studies in Antide Sitter spacetimes: Gravitational Collapse and the AdS/CFT correspondence by Daniel SantosOliván(
Book
)
2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide
In this thesis we study several open problems using Numerical Relativity on asymptotically Antide Sitter (AdS) spacetimes. The understanding of the dynamics of AdS is interesting not only because of pure theoretical reasons but also because of its importance in the correspondence gauge/gravity. In the thesis we present three different topics. The first is our research on the gravitational collapse of massless scalar fields in 18dS spacetimes. We have developed a new method that combines two different formulations of the Einstein Field Equations to get closer and with more accuracy to the collapse. The simulation starts with a Cauchy evolution with pseudospectral methods and when the collapse is taking place, it performs a change of coordinates to a characteristic one to track the formation of the apparent horizon. The collapse of the scalar field happens after a number of bounces with the critical points being the separation between the different branches. We have numerical evidence that in the separation of the branches there is a power law for subcritical configurations in addition to the one for supercritical ones. This new power law confirms that there is a gap in the mass of the apparent horizon. In the second part, we introduce a shock waves model in AdS to study the farfromequilibrium regime in the heavy ion collisions through the holographic correspondence in a nonconformal theory. Holographic collisions have attracted a lot of attention in the last few years because of the possibility of simulating strongly coupled systems but, as a drawback, we do not know yet the exact dual of the QCD that should explain the phenomena. In the models used until now, the shock waves correspond to conformal gauge theories while QCD is not conformal. In order to get closer to a description of the actual physical collisions we present the first shock wave collisions in a nonconformal theory. With this, we show how the nonconformality increases the hydrodynamisation time and also that this can happen before the equation of state is fulfilled. In the last part, we propose the use of spectral methods as a very strong option for high precision computations. Arbitrary precision arithmetic has two main problems. The first is the necessity of increasing a lot the discretisation units to reach the precision we want. The other one is the slowing down in the computational performance due to the fact that we need to emulate the fundamental operations with software because current processors are not adapted to carry out computations with precision different from the standard one. The exponential convergence of spectral methods can approximate functions to a very high accuracy with a few hundred terms in our spectral expansion while in other numerical methods it would be a few orders of magnitude larger. This makes these methods very attractive because they facilitate the accessibility to very small error simulations, removes the bottleneck of the memory demand and also help in the computational speed because fewer points are needed for the computation. We have tested this idea with the ANETO library for simulations in AdS spacetimes and the gravitational collapse in an asymptotically flat spacetime with very promising results. This library has been developed as a direct result of this thesis and that can be downloaded as Free Software
2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide
In this thesis we study several open problems using Numerical Relativity on asymptotically Antide Sitter (AdS) spacetimes. The understanding of the dynamics of AdS is interesting not only because of pure theoretical reasons but also because of its importance in the correspondence gauge/gravity. In the thesis we present three different topics. The first is our research on the gravitational collapse of massless scalar fields in 18dS spacetimes. We have developed a new method that combines two different formulations of the Einstein Field Equations to get closer and with more accuracy to the collapse. The simulation starts with a Cauchy evolution with pseudospectral methods and when the collapse is taking place, it performs a change of coordinates to a characteristic one to track the formation of the apparent horizon. The collapse of the scalar field happens after a number of bounces with the critical points being the separation between the different branches. We have numerical evidence that in the separation of the branches there is a power law for subcritical configurations in addition to the one for supercritical ones. This new power law confirms that there is a gap in the mass of the apparent horizon. In the second part, we introduce a shock waves model in AdS to study the farfromequilibrium regime in the heavy ion collisions through the holographic correspondence in a nonconformal theory. Holographic collisions have attracted a lot of attention in the last few years because of the possibility of simulating strongly coupled systems but, as a drawback, we do not know yet the exact dual of the QCD that should explain the phenomena. In the models used until now, the shock waves correspond to conformal gauge theories while QCD is not conformal. In order to get closer to a description of the actual physical collisions we present the first shock wave collisions in a nonconformal theory. With this, we show how the nonconformality increases the hydrodynamisation time and also that this can happen before the equation of state is fulfilled. In the last part, we propose the use of spectral methods as a very strong option for high precision computations. Arbitrary precision arithmetic has two main problems. The first is the necessity of increasing a lot the discretisation units to reach the precision we want. The other one is the slowing down in the computational performance due to the fact that we need to emulate the fundamental operations with software because current processors are not adapted to carry out computations with precision different from the standard one. The exponential convergence of spectral methods can approximate functions to a very high accuracy with a few hundred terms in our spectral expansion while in other numerical methods it would be a few orders of magnitude larger. This makes these methods very attractive because they facilitate the accessibility to very small error simulations, removes the bottleneck of the memory demand and also help in the computational speed because fewer points are needed for the computation. We have tested this idea with the ANETO library for simulations in AdS spacetimes and the gravitational collapse in an asymptotically flat spacetime with very promising results. This library has been developed as a direct result of this thesis and that can be downloaded as Free Software
Holographic collisions and nonconformal dynamics by Miquel Triana Iglesias(
)
2 editions published between 2017 and 2018 in Spanish and English and held by 2 WorldCat member libraries worldwide
"The gauge/gravity duality has proven to be a very useful tool in the understanding of quantum field theories outside the perturbative regime. In particular, holography has been able to shed light not only on generic mechanisms of strongly coupled theories, but also on processes occurred in experimental setups, such as the heavy ion collisions. Experimental observations such as small viscosities or fast hydrodynamization find a natural explanation when the problem is expressed in terms of gravity and black holes. Despite the successes, however, it is important to bear in mind that holography provides computational tools for toy models rather than for QCD itself, and that these models are usable only under certain assumptions. Nature is very often far more nuanced than the models physicists use to describe it. In the case of heavy ion experiments and QCD there are many features that are commonly coarse grained in the holographic computations. For instance, nontrivial RG flows or baryon currents have not been included in the holographic models until very recently, although these are very relevant to experiments, and fundamental in critical phenomena. In this thesis we present a series of works in the topics field theory and heavy ion collisions that use applied holography and numeric GR as computational tools. The unifying factor among them is that they consider gravitational setups beyond pure gravity to describe the physics of conserved currents, nontrivial RG flows and phase transitions. In chapter 2 we use an EinsteinMaxwell setup to compute the collision of two shockwaves with a conserved current and the hydrodynamization of the subsequent plasma. This conserved current is used to model the baryonic charge deposition by rapidity, observed in the experiments. The simulations are done with and without including the backreaction of the Maxwell field into the metric, which corresponds to the quenched approximation for the effects of the baryon charge on the gluons. In chapter 3 we present a one parameter family of nonconformal models. By adding an scalar field with a polynomial potential to the pure gravity setup, we can achieve a nontrivial RG flow between two fixed points in the dual field theory. In this work we compute the thermodynamics and the quasinormal modes spectra for the homogeneous states, being the latter one of the main results of the chapter. In chapter 4 we present the first holographic shockwave collisions in a nonconformal model. To do so, we use the model introduced in chapter 3. In nonconformal models the average pressure in equilibrium is not fixed by symmetry, but by the equation of state. Out of equilibrium the average pressure might take any value, giving a new probe for the equilibration of the system. When the plasma's average pressure is well approximated by the equation of state value, we say that the system has "EoSizied". In this chapter we show that the EoSization can indeed happen before the plasma has hydrodynamized. Finally, in chapter 5 we explore a holographic model that can contain phase transitions. This model is the same as the one presented in chapter 3, but now taking pure imaginary numbers for the controlling parameter. In an effort to understand the instabilities present in models with phase transitions, we trigger and evolve a spinoidal instability to its inhomogeneous end state. This is done by adding a small perturbation to a uniform black brane in a locally unstable branch, triggering a GregoryLaflamme type instability in the gravity side. The most remarkable result found in the simulation is that both the evolution and the final result are well described by second order hydrodynamics."
2 editions published between 2017 and 2018 in Spanish and English and held by 2 WorldCat member libraries worldwide
"The gauge/gravity duality has proven to be a very useful tool in the understanding of quantum field theories outside the perturbative regime. In particular, holography has been able to shed light not only on generic mechanisms of strongly coupled theories, but also on processes occurred in experimental setups, such as the heavy ion collisions. Experimental observations such as small viscosities or fast hydrodynamization find a natural explanation when the problem is expressed in terms of gravity and black holes. Despite the successes, however, it is important to bear in mind that holography provides computational tools for toy models rather than for QCD itself, and that these models are usable only under certain assumptions. Nature is very often far more nuanced than the models physicists use to describe it. In the case of heavy ion experiments and QCD there are many features that are commonly coarse grained in the holographic computations. For instance, nontrivial RG flows or baryon currents have not been included in the holographic models until very recently, although these are very relevant to experiments, and fundamental in critical phenomena. In this thesis we present a series of works in the topics field theory and heavy ion collisions that use applied holography and numeric GR as computational tools. The unifying factor among them is that they consider gravitational setups beyond pure gravity to describe the physics of conserved currents, nontrivial RG flows and phase transitions. In chapter 2 we use an EinsteinMaxwell setup to compute the collision of two shockwaves with a conserved current and the hydrodynamization of the subsequent plasma. This conserved current is used to model the baryonic charge deposition by rapidity, observed in the experiments. The simulations are done with and without including the backreaction of the Maxwell field into the metric, which corresponds to the quenched approximation for the effects of the baryon charge on the gluons. In chapter 3 we present a one parameter family of nonconformal models. By adding an scalar field with a polynomial potential to the pure gravity setup, we can achieve a nontrivial RG flow between two fixed points in the dual field theory. In this work we compute the thermodynamics and the quasinormal modes spectra for the homogeneous states, being the latter one of the main results of the chapter. In chapter 4 we present the first holographic shockwave collisions in a nonconformal model. To do so, we use the model introduced in chapter 3. In nonconformal models the average pressure in equilibrium is not fixed by symmetry, but by the equation of state. Out of equilibrium the average pressure might take any value, giving a new probe for the equilibration of the system. When the plasma's average pressure is well approximated by the equation of state value, we say that the system has "EoSizied". In this chapter we show that the EoSization can indeed happen before the plasma has hydrodynamized. Finally, in chapter 5 we explore a holographic model that can contain phase transitions. This model is the same as the one presented in chapter 3, but now taking pure imaginary numbers for the controlling parameter. In an effort to understand the instabilities present in models with phase transitions, we trigger and evolve a spinoidal instability to its inhomogeneous end state. This is done by adding a small perturbation to a uniform black brane in a locally unstable branch, triggering a GregoryLaflamme type instability in the gravity side. The most remarkable result found in the simulation is that both the evolution and the final result are well described by second order hydrodynamics."
Topics in chiral perturbation theory by
Joaquim Matias Espona(
Book
)
2 editions published between 1995 and 1996 in English and held by 2 WorldCat member libraries worldwide
2 editions published between 1995 and 1996 in English and held by 2 WorldCat member libraries worldwide
Jets as probes of strongly coupled quarkgluon plasma by Daniel Pablos Alonso(
Book
)
2 editions published between 2016 and 2017 in English and held by 2 WorldCat member libraries worldwide
In this thesis we have studied how high energetic excitations propagate through a non abelian strongly coupled plasma. This new state of matter is produced at heavy ion collisions in our accelerators and allows us to study a stage of the evolution of our Universe that occurred during the first microseconds after the Big Bang. In this extreme conditions of temperature and density the ordinary matter that we are made of behaves as a an almost perfect fluid, the most perfect known by mankind up to now in fact. The theory of strong interactions is tested at an energy scale that even though it is high enough to melt hadrons, it does not get to the point where the coupling constant is low enough to allow a perturbative description. In the plasma, the partonic field content, the quarks and gluons, cease to be the relevant degrees of freedom and a microscopic description in terms of quasiparticles is not possible. A very useful tool to put to test the actual behaviour of this strongly coupled fluid is the analysis of jet modifications as a result of their interactions with the plasma. In a first introductory part we have given the concepts needed to picture how heavy ion collisions develop as we are able to understand it today. At weak coupling, the main mechanism responsible for energy loss is induced gluon emission and interesting interference phenomena occur that lead to a dependence on path length of as the squared distance. These are known as coherence effects and their study becomes richer by considering multigluon emission, as it is done done in Part III. The strongly coupled picture uses holography to map a dressed excitation moving through a strongly coupled plasma into a string propagating in a higher dimensional space containing a black hole. Since the nonabelian theory in which the calculation is done is not QCD, but N = 4 SYM, we take these results as an insight to describe energetic parton propagation in a model of jet quenching in heavy ion collisions. Even though we assume that the exchanges with the medium are soft enough to include nonperturbative effects, as described by gauge/gravity duality, the energetic partons that are produced in the collision generally have a high virtuality which they relax by successive splittings. The latter occur at length scales that are not resolvable by the medium, and they should proceed as in vacuum. This observation motivates us to adopt a hybrid description for the interplay between the multi scale jet and the QGP, using each description at the scale it is supposed to be valid. This phenomenological description has proven to be very successful in describing dijet and photonjet data at different centralities, and predictions have been made for a wide range of observables for the coming data from run 2 of LHC, including a new observable, the ratio of the fragmentation functions of the leading and subleading jet in a dijet pair, which is highly sensitive to the specific energy loss mechanism. In the next part of the work we extend our hybrid model by the inclusion of two effects, broadening and medium response, which should help us better describe intrajet observables. The first effect, broadening, is due to the Brownian motion that probes experience in a thermal bath, and it will tend to broaden the distribution of particles within the jet. As it turns out, the observable quantifying such modifications, the jet shapes, are rather insensitive to the inclusion of this effect. However, by restricting the range of the tracks entering this analysis, we have been able to produce a new observable which shows a remarkable dependence on the precise strength of the broadening mechanism. The second effect involves overall energymomentum conservation. The rapidly thermalized energy deposited by the energetic partons modifies the plasma, inducing temperature and velocity fluctuations in the surrounding fluid cells. This perturbation propagates long distances in the form of a wake and eventually decays into soft hadrons, whose orientations keep a correlation with the jet direction and therefore produce a net effect even after background subtraction. The observable consequences are best noticed in intrajet measurements such as jet shapes and fragmentation functions, where it is clearly seen that the inclusion of such physics is in good agreement with the observed experimental trend, and it becomes simply unavoidable when comparisons against global measurements are performed. Finally, we compute the inclusive two gluon stimulated emission within the context of perturbative QCD. By studying the full answer in different kinematical limits we arrive to the conclusion that jet propagation is perceived from the point of view of the plasma as a set of effective emitters depending on the resolution power, which for a thin plasma it is of the order of the Debye screening mass. This physics is a missing piece of the Monte Carlo jet quenching model presented in this thesis and its inclusion is expected to have important consequences for the more differential observables, a task that will be undertaken in future work. These are very exciting times for the physics of strong nuclear interactions. We have seen how the very fundamental questions about the nature of the high temperature, strongly coupled phase of ordinary matter can be addressed by the study of jet quenching and its observable consequences. This thesis represents an effort in the confrontation of the seductive ideas of holography with experiments. Having the means to quantitatively confront new ideas, as we have done throughout the presented work, new observables, and new data is critical if we are eventually to understand the properties of the strongly coupled liquid quarkgluon plasma that Nature has served us
2 editions published between 2016 and 2017 in English and held by 2 WorldCat member libraries worldwide
In this thesis we have studied how high energetic excitations propagate through a non abelian strongly coupled plasma. This new state of matter is produced at heavy ion collisions in our accelerators and allows us to study a stage of the evolution of our Universe that occurred during the first microseconds after the Big Bang. In this extreme conditions of temperature and density the ordinary matter that we are made of behaves as a an almost perfect fluid, the most perfect known by mankind up to now in fact. The theory of strong interactions is tested at an energy scale that even though it is high enough to melt hadrons, it does not get to the point where the coupling constant is low enough to allow a perturbative description. In the plasma, the partonic field content, the quarks and gluons, cease to be the relevant degrees of freedom and a microscopic description in terms of quasiparticles is not possible. A very useful tool to put to test the actual behaviour of this strongly coupled fluid is the analysis of jet modifications as a result of their interactions with the plasma. In a first introductory part we have given the concepts needed to picture how heavy ion collisions develop as we are able to understand it today. At weak coupling, the main mechanism responsible for energy loss is induced gluon emission and interesting interference phenomena occur that lead to a dependence on path length of as the squared distance. These are known as coherence effects and their study becomes richer by considering multigluon emission, as it is done done in Part III. The strongly coupled picture uses holography to map a dressed excitation moving through a strongly coupled plasma into a string propagating in a higher dimensional space containing a black hole. Since the nonabelian theory in which the calculation is done is not QCD, but N = 4 SYM, we take these results as an insight to describe energetic parton propagation in a model of jet quenching in heavy ion collisions. Even though we assume that the exchanges with the medium are soft enough to include nonperturbative effects, as described by gauge/gravity duality, the energetic partons that are produced in the collision generally have a high virtuality which they relax by successive splittings. The latter occur at length scales that are not resolvable by the medium, and they should proceed as in vacuum. This observation motivates us to adopt a hybrid description for the interplay between the multi scale jet and the QGP, using each description at the scale it is supposed to be valid. This phenomenological description has proven to be very successful in describing dijet and photonjet data at different centralities, and predictions have been made for a wide range of observables for the coming data from run 2 of LHC, including a new observable, the ratio of the fragmentation functions of the leading and subleading jet in a dijet pair, which is highly sensitive to the specific energy loss mechanism. In the next part of the work we extend our hybrid model by the inclusion of two effects, broadening and medium response, which should help us better describe intrajet observables. The first effect, broadening, is due to the Brownian motion that probes experience in a thermal bath, and it will tend to broaden the distribution of particles within the jet. As it turns out, the observable quantifying such modifications, the jet shapes, are rather insensitive to the inclusion of this effect. However, by restricting the range of the tracks entering this analysis, we have been able to produce a new observable which shows a remarkable dependence on the precise strength of the broadening mechanism. The second effect involves overall energymomentum conservation. The rapidly thermalized energy deposited by the energetic partons modifies the plasma, inducing temperature and velocity fluctuations in the surrounding fluid cells. This perturbation propagates long distances in the form of a wake and eventually decays into soft hadrons, whose orientations keep a correlation with the jet direction and therefore produce a net effect even after background subtraction. The observable consequences are best noticed in intrajet measurements such as jet shapes and fragmentation functions, where it is clearly seen that the inclusion of such physics is in good agreement with the observed experimental trend, and it becomes simply unavoidable when comparisons against global measurements are performed. Finally, we compute the inclusive two gluon stimulated emission within the context of perturbative QCD. By studying the full answer in different kinematical limits we arrive to the conclusion that jet propagation is perceived from the point of view of the plasma as a set of effective emitters depending on the resolution power, which for a thin plasma it is of the order of the Debye screening mass. This physics is a missing piece of the Monte Carlo jet quenching model presented in this thesis and its inclusion is expected to have important consequences for the more differential observables, a task that will be undertaken in future work. These are very exciting times for the physics of strong nuclear interactions. We have seen how the very fundamental questions about the nature of the high temperature, strongly coupled phase of ordinary matter can be addressed by the study of jet quenching and its observable consequences. This thesis represents an effort in the confrontation of the seductive ideas of holography with experiments. Having the means to quantitatively confront new ideas, as we have done throughout the presented work, new observables, and new data is critical if we are eventually to understand the properties of the strongly coupled liquid quarkgluon plasma that Nature has served us
Grup de renormalització : tècniques i aplicacions by A Travesset(
Book
)
2 editions published between 1997 and 1998 in English and held by 2 WorldCat member libraries worldwide
2 editions published between 1997 and 1998 in English and held by 2 WorldCat member libraries worldwide
Chiral Imbalance in Hadron Matter: Its Manifestation in Photon Polarization Asymmetries by
A. A Andrianov(
)
1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide
1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide
QCD with Chiral Chemical Vector: Models Versus Lattices by
A. A Andrianov(
)
1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide
1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide
Confinement in pure Gauge theories by
Luca Tagliacozzo(
)
2 editions published in 2006 in English and held by 2 WorldCat member libraries worldwide
2 editions published in 2006 in English and held by 2 WorldCat member libraries worldwide
Analytical and numerical studies of random surface models and the QCD string by
Aleix Prats Ferrer(
)
1 edition published in 2005 in English and held by 1 WorldCat member library worldwide
1 edition published in 2005 in English and held by 1 WorldCat member library worldwide
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 Pich, A. (Antonio) Editor
 Andrianov, Alexander Editor
 Andrianov, Vladimir Editor
 Kolevatov, Sergei Editor
 Universitat de Barcelona
 Universitat de Barcelona Departament d'Estructura i Constituents de la Matèria
 Universitat de Barcelona Departament de Física Quàntica i Astrofísica
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 Andrianov, A. A. Author
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