Facultad de Física
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- ItemSelf-assembly of submonolayer-coverage organic films(2009) Corrales Iturriaga, Tomás Patricio; Volkmann, Ulrich; Pontificia Universidad Católica de Chile. Instituto de FísicaIn this work we present a study of self assembled submonolayer coverage organic films. The types of molecules studied here are n-alkane chains, mainly n-dotriacontane (n-C32H66), that are deposited on silicon substrates with a thin native silicon oxide layer (∼15Å). In this research we have developed a velocity controlled dip-coating device to prepare submonolayer films. We have identified the parameters that affect the coverage, morphology and structures that arise in the preparation of the film. The techniques used to characterize these films are Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Fur- thermore, this is the first work that demonstrates that SEM is a plausible technique to study thin films of n-alkanes. The future importance of this research is related to the possibility of micro-structuring energetically homogenous surfaces with nanometer thick films using relatively simple techniques, such as velocity controlled dip-coating. Micro-structured patterns, such as the stripes reported here, could be applied as optical diffraction grids or as templates for other materials.In this work we present a study of self assembled submonolayer coverage organic films. The types of molecules studied here are n-alkane chains, mainly n-dotriacontane (n-C32H66), that are deposited on silicon substrates with a thin native silicon oxide layer (∼15Å). In this research we have developed a velocity controlled dip-coating device to prepare submonolayer films. We have identified the parameters that affect the coverage, morphology and structures that arise in the preparation of the film. The techniques used to characterize these films are Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Fur- thermore, this is the first work that demonstrates that SEM is a plausible technique to study thin films of n-alkanes. The future importance of this research is related to the possibility of micro-structuring energetically homogenous surfaces with nanometer thick films using relatively simple techniques, such as velocity controlled dip-coating. Micro-structured patterns, such as the stripes reported here, could be applied as optical diffraction grids or as templates for other materials.
- ItemCaracterización de propiedades clásicas y cuánticas de pulsos de femtosegundos(2017) Rojas Aedo, Ricardo; Seifert, Birger; Pontificia Universidad Católica de Chile. Facultad de FísicaEste informe de tesis versa sobre propuestas hacia la caracterización de las propiedades clásicas y cuánticas de pulsos de femtosegundos, que en principio pueden ser expandidas a pocos pico segundosy a atto segundos, al menos en su sentido conceptual. El texto principalmente analizará en detalle el método de caracterización de propiedades clásicas de pulsos, basado en la mezcla no lineal de diferentes trenes pulsados, llamado FROG, reinterpretando el campo mezcla, desde una perspectiva clásica, donde se desarrolla una nueva técnica de caracterización analítica y no interferométrica llamada “VAMPIRE analítico” , y otra perspectiva cuántica, donde surge una propuesta para el análisis de las propiedades cuánticas internas de pulsos haciendo uso de esquemas tipo FROG . Por completitud en la última línea, además se comentará como generar estados cuánticos interesantes (no-coherentes), y los resultados obtenidos experimentalmente en el laboratorio, con pulsos de femtosegundos utilizando fibras ópticas.
- ItemAsirunaka: Generador de Potencia Pulsada de Doble Pulso Dedicado a Plasmas de Explosión de Alambres y Formación de Nanopartículas(2017) Masoliver Aguirre, Pavel; Bhuyan, Heman; Pontificia Universidad Católica de Chile. Facultad de Física
- ItemNumerical simulations of wire array Z-pinches under variations of global magnetic fields(2017) Donoso Tapia, Luis Alberto; Veloso Espinosa, Felipe Eduardo; Pontificia Universidad Católica de Chile. Facultad de FísicaDuring the last five years a lot of work has been done with the computational code GORGON [1,2] to simulate the dynamics of transient plasmas. The main work has been focused on studying plasmas in different configurations of wire arrays.These configurations include conical arrays [3,4,5], asymmetrical cylindrical arrays [6].This thesis focuses on two primary areas. First, how does spatial resolution affect the reliability of observed simulation results? This was studied by simulating conical wire array Z-pinches with varying resolutions. Second, the dynamics of Z pinch plasmas generated by asymmetrical wire arrays are examined. This causes the magnetic field topology to become asymmetrical, this causing the plasma to move away from the geometrical center [6]. Regarding the conical arrays studied in this work, a low electronic density region was initially observed, which was located between two high density regions, similar to what has been observed in stellar phenomena like the Herbig-Haro objects [7]. However, subsequent simulations, with resolution increased by a factor of 2,5,have disproved this supposition.The second main aspect of this work shows how undermassed aluminium wire configurations can be used for accurate control of plasma dynamics, by modifying the governing magnetic field topology of the system. This leads to an acceptable method for controlling the direction and velocity of the plasma precursor within a time period similar to the associated pulsed power generator rise time [6,8,9].
- ItemOptical surface monitoring and pillow positioning configuration for complex system's set-up(2017) Loreto Javiera Godoy Solís; Häring, Peter, 1965-; Sánchez Nieto, Beatriz; Pontificia Universidad Católica de Chile. Facultad de FísicaOptical Surface Monitoring and Pillow Positioning Configuration for Complex System’s Set-Up: Aligning the patient’s target volume, isocenter and OARs with the linac’s isocenter can be done using certain immobilization device and imaging to adapt therapy if any variation of the tumor or patient’s body has occurred. In this investigation, a configuration of 10 pillows and Vision RT were employed to positioning the patient while it was checked by CBCT. The results show that for non-coplanar fields, Vision RT is accurate enough, with shifts less than 1º and 1mm. 4 pillows in a wedge under the head show an accurate position in the rotational axis (lessthan 1º) comparing with Vision RT and the off-set values given by the CBCT, although more pillows should be necessary for thorax and pelvis plans, since the differences between both methods are in average of 5 mm and 10º. Since the image registration was made manually, there are difference between 2 CBCTs of 6 mm and 5º in average in each plan, around the same magnitude than the difference between the two methods, so the differences might be due to the fact that Vision RT matches surfaces and CBCT matches the target volume, and because the manual image registration is involved with a human error
- ItemForce spectroscopy of a saxitoxin bindingaptamer(2017) Figueroa Leigh, Nataniel; Maze Ríos, Jerónimo; Pontificia Universidad Católica de Chile. Facultad de FísicaOver the last decades optical tweezers have enabled the exploration of pico-Newton forces involved in several single-molecule mechanisms relevant in important biological systems (ie. DNA-folding and molecular motors). This has lead to a new understanding of the mechanical nature of the interactions occuring between biologicaly-relevant molecules. Here, in this thesis we used optical tweezers to study the folding/unfolding dynamics of the Handy-aptamer, a single-stranded-DNA molecule with high affinity for saxitoxin, a potent neurotoxin that is present in red tide algal blooms. This is the cause of substantial economic damage to the shellfish industry. To perform the pulling experiments, we developed a method to chemically attach the Handy-aptamerin between two double-stranded-DNA handles, which themselves were attached tomicron-sized polystyrene beads that were manipulated using the optical tweezers and a micropipette. From the pulling experiments we observed sharp folding/unfolding transitions. None the less, the transition between these states was observed to be erraticand time-dependent, exhibiting changes in sharpness and rate of occurence. Weattempted to stabilize the structure of the aptamer by adding Mg+2 and saxitoxin, both giving similar results; making the rip (sudden transition in extension) force histograms narrower and less abudant at higher forces; implying structure stabilization.These results have been the first steps towards characterizing the folding properties of the Handy-aptamer and identifying the properties that make it bind to saxitoxin.This would prove useful to develop better saxitoxin identifiers and sensors that would have lower toxin surveying costs and prevent deaths.
- ItemGas adsorption properties of complex copper oxides(2017) Rojas de la Fuente, Susana Dennis; Cabrera, Alejandro Leopoldo; Pontificia Universidad Católica de Chile. Facultad de FísicaHighly epitaxial films of CuFeO2 and CuFe0.75Ga0.25O2 were grown by pulsed laserdeposition (PLD) from stoichiometric targets over Al2O3 (001) substrate undercontrolled partial pressure of oxygen as carrier gas. Resulting films were highly orientedin c-axis direction.Structural properties of samples were characterized by X-Ray Diffraction (XRD), Raman spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), optical transmittance and diffuse reflectance. This characterization techniques confirmed the rhombohedral Delafossite crystal structure for both kind of samples and CuFe0.75Ga0.25O2 samples were formed by an alloy between CuFeO2 and CuGaO2 Delafossite materials. Using optical transmittance and diffuse reflectance, the optical transitions were estimated by using theTauc method. Direct optical transitions were measured at 1.28±0.02 eV and 2.20±0.05eV for pure CuFeO2 samples and for CuFe0.75Ga0.25O2 were measured at 1.50±0.04 eVand 2.30±0.09 eV, plots showed another higher transition near 3 eV but due to technical limitations this gap cannot be clearly determined. Adsorption of CO2 and H2O was studied via thermal programmed desorption technique. In both films Copper and Iron were present at the surface, and consequently formed part of the surface-gas interface. X-ray photoelectron data indicated that CO2 is adsorbed preferentially at copper sites forming a similar coordination to CuCO3. The energy for desorption of CO2 and H2O was estimated to be 1.0±0.8 eV/molecule for CuFeO2 and0.7±0.4 eV/molecule for CuFe0.75Ga0.25O2. Also, it was possible to correlate second order desorption with a CO2 reduction reaction. Copper Delafossite materials studied in this work showed some catalytic activity in good agreement with the literature. Future work in this field would involve synthesis of a wider variety of CuFe1-xGaxO2 samples in order to get a better idea of the influence ofiron substitution for gallium in the Delafossite structure. Also, for a better understanding of the relationship between adsorption properties and catalytic behavior some futurework regarding electrical and electrochemical properties is proposed
- ItemFotodetección mediante interferometría y sintonización termomecánica de láseres.(2017) Godoy Montecinos, Sergio Juan Pablo; Wallentowitz, Sascha; Pontificia Universidad Católica de Chile. Facultad de FísicaEsta tesis esta constituida por trabajos que se pueden agrupar en dos partes. La primera es sobre usos de un montaje homodino para hacer interferometría óptica, donde se presenta una medición de anticorrelaciones entre las fotodetecciones de las salidas de un separador de haces con reflexiones internas, utilizando una fuente de luz de estado coherente, y trabajos sobre como obtener la fotoestadística de una señal óptica utilizando un sistema homodino de interferometría. En la segunda parte se presenta la construcción de un láser de cavidad externa cuya frecuencia es sintonizable por medio de un control de temperatura.
- ItemWetting properties of n-alkane thin films to understand the adherence mechanism of artificial membranes on silicon substrates(2017) Díaz Díaz, Diego Ignacio; Volkmann, Ulrich; Pontificia Universidad Católica de Chile. Facultad de FísicaIn this work we present a study of the wetting properties of silicon samples coated with a single layer of n-alkane molecules that self-assemble perpendicular to the surface.The types of molecules studied here are n-alkane chains, mainly n-dotriacontane (n-C32 H66), that were deposited on silicon substrates with a thin native silicon oxidelayer (15˚A). The thin films were prepared by Dip-Coating technique in a C32 H66/n-heptane solution. The techniques used to characterize these films are Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). In this research a contact angle setup was developed to measure wettability of submonolayer films. An influence of morphology and coverage on the contact angle was found. Moreover, alkane molecules migrate much like a reverse coffee-ring effect after drop evaporation, forming complex tail-like morphologies.This research is relevant to understand alkane adhesion on silicon substrates, which is related with artificial membrane fabrication, which are used for biosensors applications. Micro-structured pattern like stripes could be applied as templates for other materials, especially considering the possibility of creating homogeneous surfaces with nanometer thick films.
- ItemIndividual breast dosimetry for mammographic exams : a back-projection approach(2017) Rioseco Mora, Camila Belén; Sánchez Nieto, Beatriz; Dörner Yaksic, Edgardo Andrés; Häring, Peter; Pontificia Universidad Católica de Chile. Facultad de FísicaThe aim of this project is to propose and validate a procedure for estimating a dose at the axial plane of the breast in patients under mammographic exposure by means of electronic portal imaging device (EPID) dosimetry. In vivo transit dosimetry consists of measuring the transmitted radiation through the breast with an EPID, and then back-projecting the fluence through the same volume in order to reconstruct the dose at a certain plane. The methodology relies on the fact that from individual beam attenuation information, is possible to estimate dose deposition in the mammary gland. Beam attenuation was calculated from the exit and entrance fluence. Monte Carlo simulation of the entrance fluence was computed for three beam qualities. Exit fluence is calculated for each case, by deconvolution of the EPID image with previously determined composite kernel. A complete model (i.e., X-ray tube, breast compression paddle, different breast thickness and detector) of the GE Senograph Essential with Tomosynthesis device, was simulated with EGSnrc. Specific codes as BEAMnrc and DOSXYZnrc were used for beam and detector simulations, respectively. Three different beam qualities were simulated (only for 2D conventional mammography image acquisition) and additionally, and in-house graphical user interphase MATLAB1 program “BreDose” was designed to estimate doses at an axial mid-plane of the breast from the EPID images.
- ItemParametrización y aplicación de un potencial de muchos cuerpos y transferencia de carga para Fe y FeF2(2017) Tangarife Franco, Edwin; Mejía López, José Félix; Pontificia Universidad Católica de Chile. Facultad de FísicaLas simulaciones computacionales a nivel atómico juegan un papel importante en el desarrollo, diseño y optimización de materiales, así como en la comprensión de sus propiedades estructurales, físicas y químicas. Los mejores enfoques que actualmente existen para describir las interacciones atómicas se basan en las descripciones mecánico-cuánticas, pero son computacionalmente muy costosas y su aplicación generalmente se limita a situaciones en las que el número de átomos es pequeño. Para estudiar sistemas de mayor tamaño se utilizan descripciones empíricas como el potencial COMB (carga optimizada de muchos cuerpos) que describe la interacción de átomos cargados, tomando en cuenta la posible transferencia de carga. Esto es importante principalmente en el estudio de sistemas iónicos, como los óxidos y los halogenuros, cuando se quiere investigar sus notables propiedades como catalizadores, disolventes, refrigerantes, etc. En el caso particular del Fluoruro de Hierro (FeF2), un sistema iónico antiferromagnético, ha sido usado también para la investigación básica del fenómeno de exchange bias en acoplamiento con un ferromagneto como el hierro (Fe). Este fenómeno depende fuertemente de la estructura geométrica y magnética de la interfaz generada en el acoplamiento del FeF2 y el Fe, cuya información no es fácil de obtener desde medidas experimentales. A nivel atómico este acoplamiento puede modificar la distribución de carga de las superficies de cada uno de los materiales en contacto, así como también podría tener migración de átomos de la superficie Fe a la superficie de FeF2, generando una magnetización no compensada que es necesaria para obtener el efecto de anisotropía unidireccional responsable del fenómeno de exchange bias. Por lo tanto, para simular estos sistemas a través de Monte Carlo o simulaciones de dinámica molecular, es importante considerar la transferencia de carga en el potencial de interacción utilizado para describir el sistema. En este trabajo se propone una parametrización para el potencial COMB, aplicados a sistemas compuestos por Fluoruro de Hierro y Hierro metálico (FeF2/Fe). El potencial empírico toma en cuenta los efectos de la transferencia de carga y las interacciones de muchos cuerpos dependientes del ambiente químico local que experimentan los átomos. El potencial es parametrizado pormedio de propiedades experimentales reportadas y/o calculadas desde primeros principios de las fases estables para Fe y FeF2 como: energía de disociación para moléculas de Fluor neutra F2 e ionizada F2−1, parámetros de red para el estado fundamental Fe y FeF2 y constantes elásticas. Esta parametrización es probada con simulaciones de dinámica molecular sobre estructuras macroscópicas cristalinas, superficies, nanopartículas y agregados atómicos. Principalmente se realiza un detallado estudio de la interfaz de FeF2/Fe, mostrando que existe difusión atómica desde el material antiferromagnético (FeF2) hacia el material ferromagnético (Fe). El tamaño de la interfaz obtenida es de 1.4 nm y se observa una fase amorfa que es activada por el proceso de disminución de la temperatura desde 1500K hasta 10K.
- ItemDesign of microwave antennas for nitrogen-vacancy centers applications(2018) Ortiz Moreno, Ari Rolando; Maze Ríos, Jerónimo; Gence, Loik; Pontificia Universidad Católica de Chile. Facultad de FísicaNitrogen-vacancy centers in diamond are promising candidates for a wide range of applications due to their quantum sensing capabilities at room temperature and easy optical readout and manipulation by means of confocal microscopy and the application of microwave radiation. Applying microwave radiation is not a trivial task depending on the application. If a single NV center is addressed, then a thin (20 —m diameter) copper wire is sufficient if the NV is within 50 —m from the wire. However in a large area with a lot of NV centers that must be addressed simultaneously with a homogeneous microwave intensity, then a more specialized microwave antenna is required. Towards this goal, a complete procedure for developing microstrip antennas for NV centers applications is presented. In order to drive all NV centers that point along a given direction with the same intensity, an antenna with a uniform intensity over this area is needed, which is not a trivial task. At a given power, there is a compromise between a uniform intensity and high intensity. This procedure includes the antenna design using optical lithography in order to achieve the desired spatial resolution, fabrication and testing using a vector network analyzer and different diamond samples. The fabricated antennas reached a maximum transmission of around 40% near the desired frequency (2.87 GHz), a 100 MHz bandwidth and are capable of resolving electronic spin resonance with a maximum contrast of 22%.
- ItemCharacterization of the ionizing radiation emission of a plasma focus device(2018) Díaz Contreras, Daniela Alejandra; Caprile Etchart, Paola F.; Moreno Martínez, José; Schwahofer, Andrea; Pontificia Universidad Católica de Chile. Facultad de FísicaThe PF2kJ plasma focus device was studied as a pulsed source of x-rays neutron radiation. X-rays are emitted during the focalization process of the plasma if the device is operated using hydrogen as the filling gas. Fusion reactions can be obtained if deuterium gas is used, with the consequent emission of fast neutrons. The x-ray emission is characterized by spatial distribution measurements by using TLD100 dosimeters and radiochromic films, the linearity of the output, as well as the effective energy of the x-ray radiation by measuring transmission through different aluminum thicknesses. A low effective energy of 7.5 keV is estimated. The variation of the intensity of the emission in distance and the assessment of the radiation levels which a device operator may be exposed are also included as part of the x-ray emission characterization study. Personal equivalent dose value of 2.8 mSv/year is estimated in a normal regime of the device operation. This level is not harmful based on ICRP recommendations. Fast neutron fluence of the order of 105n/cm2per shot in 4π sr is estimated by means of 3He proportional detector, and preliminary measurements are performed by using pairs of TLD 600 and TLD 700 dosimeters.
- ItemPredictors for radiation-induced xerostomia and their reliability considering random setup errors and parotid gland migration(2018) Astaburuaga García, Rosario; Bangert, Mark; Pontificia Universidad Católica de Chile. Facultad de Física
- ItemDesarrollo e implementación de un sistema de auditoría para dosimetría absoluta con alanina y TLD en centros de radioterapia chilenos(2018) Faúndez Cifuentes, Daniel; Gago Arias, Araceli; Pontificia Universidad Católica de Chile. Facultad de Física
- ItemDeviations of the leptonic branching ratios of the heavy Higgs in the MSSM with broken R-parity(2018) Méndez Leiva, Andrés; Díaz, Marco A.; Pontificia Universidad Católica de Chile. Facultad de FísicaWe performed a phenomenological study of the leptonic decay modes of a heavy Higgs in a supersymmetric scenario which we called the ϵλ-MSSM, in which we added ϵ-bilinear and λ-trilinear terms to break R-parity explicitly, constrained by the most recent neutrino experimental data. In particular, we explored the possibilityof decreasing the coupling associated to the τ τ mode, in order to reduce the large number of events predicted by other typical R-parity conserving (RpC) models to justify the non-observation of any heavy scalar resonance, while opening regions of the parameter space which were previously excluded. We also study the possibility of enhancing the µµ mode due to its importance in future experimental searches. We found that even with a loose cosmological bound given by the sum of the neutrino masses, the deviations for the τ τ mode are smaller than a 1%, while for the µµ mode it can be up to 50%. However, once we constrained our parameters to reproduce the most recent neutrino observables associated with neutrino oscillation, we found that the deviations attained in each mode are extremely small, leading to deviations of ∼ 0.0001% for the µµ mode and ∼ 0.0000000001% for the τ τ model, making the ϵλ-MSSM indistinguishable from the RpC-MSSM case in the leptonic channels.
- ItemEvaluación dosimétrica de tratamientos con Leksell gamma knife en presencia de inhomogeneidades(2018) Elgueda Farías, Susan Pamela; Caprile Etchart, Paola F.; Pontificia Universidad Católica de Chile. Facultad de Física
- ItemDeterminación de dosis absorbida periférica a través de simulaciones Monte Carlo : evaluación de los algoritmos de cálculo en el planificador comercial Monaco®(2018) Rodríguez Mongua, José Luis; Dörner Yaksic, Edgardo Andrés; Pontificia Universidad Católica de Chile. Facultad de FísicaSe ha realizado la simulación Monte Carlo en EGSnrc del acelerador lineal Axesse de Elekta para la obtención de distribuciones de dosis tanto dentro como fuera del campo de radiación de un haz de 6 MV. Dicha simulación ha sido validada por comparación con medidas experimentales. Posteriormente, el modelo Monte Carlo de EGSnrc del acelerador fue aplicado a la evaluación del comportamiento de los algoritmos Collapsed Cone y Monte Carlo de Monaco® en el escenario de una planificación clínica de un tratamiento de pulmón con tres campos sobre el maniquí computarizado masculino del ICRP110. Para lograr este objetivo hubo que transformar el formato original del maniquí ICRP en otro compatible con EGSnrc y con el DICOM que admite el sistema de planificación comercial, así como segmentar las estructuras para el cálculo de la dosis a órgano. La comparación de los resultados se realizó a partir de diversas métricas derivadas de los histogramas dosis volumen. Se encontró que la simulación Monte Carlo de EGSnrc para estimación de dosis periférica, debe ser realizada sin el uso de técnicas de reducción de varianza como el DBS puesto que esto altera de forma importante el computo de dosis fuera del campo. Los resultados obtenidos revelan que Collapsed Cone infraestima la dosis en un 40% cercano al borde del campo (arrastrando la falta de veracidad del sistema dosimétrico empleado en el comisionamiento) y que ambos algoritmos pueden llegar a subestimar la dosis en órganos alejados del borde del campo en más de un 80%. Sin embargo, en general Collapsed Cone reporta valores más cercanos al Monte Carlo de EGSnrc excepto en puntos muy alejados del campo de tratamiento y alineados con el isocentro. El hecho de que Collapsed Cone tenga un mejor comportamiento general puede deberse a que el Monte Carlo de Monaco fue optimizado para tratamientos con modulación de la fluencia.
- ItemLímites en la detección de neutrinos estériles en experimentos de reactores nucleares(2018) Mora Lepin, Luis; Ochoa-Ricoux, Juan Pedro; Pontificia Universidad Católica de Chile. Facultad de FísicaEn las últimas décadas el desarrollo de diversos experimentos para detectar neutrinos ha permitido ampliar el conocimiento de estas partículas a un nivel sin precedentes. A pesar del gran desarrollo en el área, existen aún algunas interrogantes sin respuesta. Una de ellas es establecer si es que existen más que sólo tres generaciones de neutrinos. En particular, existen algunas observaciones experimentales [1, 2, 24] que podrían ser explicadas por la existencia de un cuarto tipo de neutrino, el cual se ha denominado como “neutrino estéril” debido a que no interactuaría con la materia mediante ninguna de las fuerzas del Modelo Estándar. El presente trabajo investiga la posible existencia de un neutrino estéril mediante una reproducción estadística de las observaciones del experimento Bugey-3 en combinación con las del experimento Daya bay. Adicionalmente, se presenta un estudio del potencial de los experimentos PROSPECT y el detector cercano de JUNO en la búsqueda de neutrinos estériles mediante el uso de simulaciones. La segunda interrogante de la física de neutrinos que será investigada en esta tesis guarda relación con la jerarquía de masas de los neutrinos, la cual es aún desconocida. Se estudiará el potencial de JUNO para lograr resolver la jerarquía de masas y cómo la modificación de distintos parámetros experimentales influyen en la sensibilidad del experimento.
- ItemTesting modified gravity using a marked correlation function(2018) Armijo Torres, Joaquín; Padilla, Nelson; Cai, Yan-Chuan; Pontificia Universidad Católica de Chile. Facultad de FísicaEn teorías de gravedad modificada que presentan mecanismo de apantallamiento camaleón, la fuerza de la quinta fuerza depende del ambiente donde es gatillada. Esto induce una dependencia del entorno en la formación de la estructura a gran escala, que difiere del Universo ΛCDM. Se muestra que tales diferencias pueden ser captudaradas por medio de una función de correlación marcada. Con la función de correlación de galaxias y su número de densidad calibrado para ser el mismo entre los modelos f(R)y ΛCDM, en simulaciones numéricas, mostramos que la función de correlación marcada usando la densidad local o la masa de los halos para marcar las galaxias, contiene información extra y puede ser usada para probar estas teorías. Discutimos las posibles aplicaciones de este estudio estadístico in observaciones. Esta tesis reproduce texto de Armijo et al. (2018) literalmente.