5D Black Rings and 4D Black Holes

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小学上册第一次英语第三单元期末试卷

小学上册第一次英语第三单元期末试卷

小学上册英语第三单元期末试卷英语试题一、综合题(本题有100小题,每小题1分,共100分.每小题不选、错误,均不给分)1.What do you call a large body of water surrounded by land?A. LakeB. OceanC. RiverD. SeaA2.The ancient Egyptians built their pyramids as _____.3.How many zeros are in one thousand?A. OneB. TwoC. ThreeD. Four4.In art class, we use crayons, markers, and ________ (水彩) to create beautiful pictures. I love expressing my ________ (创造力).5.In 1776, the Declaration of Independence was adopted in the ______ (美国).6.I love exploring new places. Every summer, my family goes on a trip to __________. We visit museums, parks, and try local foods.7.The __________ is the imaginary line that divides the Earth into the Northern and Southern Hemispheres.8.The zebra has black and ______ (白色) stripes.9.The city of Nicosia is the capital of _______.10. A deer uses its keen sense of smell to detect ________________ (危险).11.How many colors are in a rainbow?A. FiveB. SixC. SevenD. EightC12.My brother loves to __________ (参加) sports tournaments.13.What is the name of the first artificial satellite launched into space?A. Sputnik 1B. Explorer 1C. Vanguard 1D. Luna 114.What is the capital city of Finland?A. HelsinkiB. TampereC. OuluD. Espoo15.She has a _____ (新) dress.16.What do we call a person who writes books?A. AuthorB. ArtistC. ComposerD. DirectorA17.The ____ has a loud call and is often found near water.18.I want to be a ________ when I grow up.19.We have a ______ (快乐的) time during family vacations.20.Elements in the same column of the periodic table have similar _______.21.What do we call a person who studies marine life?A. Marine BiologistB. OceanographerC. Aquatic ScientistD. All of the above22.She _____ (plays/played) piano well.23.Saturn is known for its beautiful _______.24.I watched a _______ (小鸟) build a nest.25. A solution that contains a high concentration of ions is called a ______ solution.26.What is the main theme of the story "Little Red Riding Hood"?A. FriendshipB. AdventureC. DangerD. Love27.Rocks are classified into three types: igneous, sedimentary, and ______.28.What is the term for a baby dog?A. KittenB. PuppyC. CalfD. CubB29. A bison is often seen in ______ (草原).30.This ________ (玩具) inspires me to be creative.31.I need to _____ (finish/start) my homework.32.What is the name of the main character in "The Little Mermaid"?A. ArielB. BelleC. CinderellaD. ElsaA Ariel33.I enjoy ______ (与朋友相处).34.What is the capital of Malta?A. VallettaB. MdinaC. RabatD. SliemaA Valletta35.What do you call the study of human societies and cultures?A. SociologyB. AnthropologyC. PsychologyD. Political scienceB36.What do we call a drawing or picture made with a pencil?A. PaintingB. SketchC. PhotoD. CollageB37.The spider spins a _________. (网)38.My _____ (小狗) loves to fetch sticks.39.听一听,判断所听内容与图片是否相符。

宇宙英文作文故事

宇宙英文作文故事

宇宙英文作文故事Title: Exploring the Cosmos: A Journey into the Unknown。

In the vast expanse of the cosmos, where stars twinkle like distant dreams and galaxies spiral in infinite dance, lies the boundless frontier of human exploration. This isthe story of intrepid adventurers who dared to venture beyond the familiar confines of Earth, reaching out intothe depths of space in search of understanding, discovery, and wonder.Our tale begins with the pioneers of space exploration, whose vision and courage paved the way for humanity's first steps beyond our planet's atmosphere. In the 20th century, amidst the tensions of the Cold War, the United States and the Soviet Union engaged in a race to conquer the cosmos. The launch of Sputnik by the Soviets in 1957 marked the dawn of the space age, sparking a fervent competition to achieve milestones such as the first human in space and the first manned lunar landing.In 1969, the world held its breath as Neil Armstrong and Buzz Aldrin set foot upon the lunar surface, uttering immortal words that echoed across the void: "That's one small step for man, one giant leap for mankind." Their historic feat not only demonstrated the triumph of human ingenuity and determination but also opened the door to a new era of exploration.As the decades passed, humanity's reach extended ever deeper into the cosmos. Robotic probes ventured to the outer planets, capturing breathtaking images of Jupiter's swirling storms, Saturn's majestic rings, and the icy moons of Neptune and Uranus. Meanwhile, space telescopes like Hubble peered into the distant reaches of the universe, revealing galaxies billions of light-years away and shedding light on the mysteries of dark matter and dark energy.But the quest for understanding did not end with the confines of our own solar system. In the 21st century, ambitious missions set their sights on distant worldsbeyond, searching for signs of life amidst the stars. The Mars rovers trundled across the red desert sands, analyzing soil samples and probing for evidence of ancient water and organic molecules. Elsewhere, telescopes scanned the skies for exoplanets orbiting distant stars, tantalizing astronomers with the possibility of other Earth-like worlds teeming with life.Yet, as humanity's reach extended further into the cosmos, so too did our awareness of its vastness and complexity. We learned of the violent birth and death of stars, the relentless pull of black holes, and the delicate balance of forces that govern the fabric of spacetime itself. And amidst the grandeur of the cosmos, we found humility in our own insignificance, mere specks of dust adrift in the cosmic ocean.But for all our knowledge and understanding, the cosmos remains a realm of endless possibility and discovery. With each new mission, each new observation, we peel back another layer of the cosmic tapestry, revealing new wonders and new mysteries that beckon us ever onward. For as longas there are stars in the sky and worlds beyond our own, the human spirit of exploration will continue to soar, driven by an insatiable curiosity to know and understand the universe that surrounds us.。

我有一个好梦英语作文小学六年级

我有一个好梦英语作文小学六年级

我有一个好梦英语作文小学六年级I Had a Beautiful DreamLast night, I had the most wonderful dream. It was so vivid and real, like I was actually living it. When I woke up, I felt happy and inspired, and I wanted to write it all down before I forgot.The dream started out in my classroom at school. It was an ordinary day, and my teacher Mrs. Johnson was giving a lesson about planets and the solar system. She asked if anyone knew which planet was the largest, and I raised my hand excitedly because I knew the answer was Jupiter. Mrs. Johnson called on me, and I stood up feeling proud that I would get the answer right.But then, everything started changing and becoming strange and dreamlike. The classroom seemed to melt away, and I found myself standing in outer space, surrounded by stars and planets! I could see the rings of Saturn up close and the reddish surface of Mars. I tried to move but I was just floating weightlessly. It was amazing but also a bit scary at first.Then, I heard a friendly voice calling out to me. "Don't be afraid! Come with me and I'll show you the wonders of the universe." I turned around and saw a glowing figure that lookedalmost like an angel or an alien. It had a human shape but its body seemed to be made of stardust and galaxies swirled around inside of it.The cosmic being reached out its hand, and I felt myself being pulled gently toward it. Suddenly, we were zooming through the cosmos at incredible speeds, slipping through wormholes and around black holes. I watched whole star systems and nebulae bloom and die in the blink of an eye. We explored strange new worlds, some frozen in ice, others filled with oceans and jungles teeming with alien life.On one planet, I met a race of six-legged creatures with vibrant blue fur and big yellow eyes. They didn't speak with words but could communicate telepathically. Their minds felt warm and curious as they welcomed me and showed me their crystalline city nestled in a lush green valley.On another world, I walked among giants – people who towered fifty feet tall! Their booming voices shook the ground, but they were gentle and let me clamber over their enormous hands and feet. A little girl from their village no bigger than a human played with me, and we became fast friends despite the huge difference in our sizes.We went to so many unbelievable places, I can't really describe them all. One minute I was hiking through a petrified forest of rainbow-colored trees, and the next I was surfing down the gullets of a gas giant, waves of liquid nitrogen and hydrogen crashing around me. It felt like the dream would never end and the adventures would just keep getting wilder and more amazing.Eventually, my celestial guide brought me to the very edge of the known universe. We stood there together, watching galaxies being formed from clouds of cosmic dust billions of light years away. "This is where it all began, and where it will all return in the end when the last stars blink out," the entity told me solemnly.I felt very small realizing how vast the cosmos truly is. At the same time, I felt a profound sense of peace and connection to all that exists. Like I was a tiny but vital part of this grand,never-ending cycle of birth, life, death, and rebirth among the stars.Sadly, that's when I began to wake up, my consciousness returning to the ordinary reality of my bedroom. I opened my eyes, the amazing visions already fading from my mind's eye.But the feelings of wonder and existential calm have stayed with me.Maybe it was just a crazy dream caused by watching too many space movies. Or maybe my spirit really did get to take a whirlwind tour of the infinite universes out there, guided by some higher being or force. Either way, I know I'll never look at the night sky or think about our cosmic origins the same way again.When I was little, I wanted to be an astronaut and travel to the Moon and Mars. But after this dream, I feel like I've already been to places that make the Moon seem pretty ordinary in comparison. Exploring other planets or even other galaxies doesn't seem so far-fetched or impossible anymore. In fact, I think human beings are destined to one day voyage among the stars, just like I did in my dream.I hope that I can have dreams that amazing again. For now though, I'll have to be content with learning as much as I can about astronomy and the universe we live in. I've got a new telescope for my bedroom that I'm going to spend a lot of time with, scanning the night skies. And I'm already devouring every book about space I can get my hands on from the library.Who knows? Maybe my incredible cosmic dream was really a vision of my own future. Maybe one day, I'll be an astronaut or scientist uncovering the secrets of life among the stars. Or perhaps I'll write science-fiction stories that will inspire other kids to develop a fascination with the infinite wonders of the universe, just like my dream has inspired me. All I know is, the boundaries of what's possible for me to experience and achieve now seem to extend far beyond the limits of this small planet we call home.。

以天文摄影展为题的英语作文高中

以天文摄影展为题的英语作文高中

以天文摄影展为题的英语作文高中全文共10篇示例,供读者参考篇1Hello everyone! Today I want to tell you all about the amazing astronomy photography exhibition that I went to with my family last weekend. It was so cool!We saw pictures of the stars, planets, and galaxies that were taken by really talented photographers. Some of the pictures were so beautiful and colorful, it was like looking at a magical wonderland in the sky.There was a picture of the moon that showed all the craters and mountains in such clear detail. It was like I could reach out and touch it! And there was a picture of Jupiter with its big red spot, it looked so mysterious and fascinating.My favorite picture was of the Milky Way galaxy. It was a swirl of bright stars and colors that made me feel like I was flying through space. I could have stared at it for hours!I also learned a lot of cool facts about space while I was at the exhibition. Did you know that the sun is a star too? And thatthere are planets out there that are much bigger than Earth? It was mind-blowing!I had so much fun at the astronomy photography exhibition.I can't wait to go back and learn even more about the universe. Space is so amazing and mysterious, and I want to explore it all!篇2The Astronomy Photography ExhibitionHey everyone! Today I want to tell you about this super cool event I went to last weekend – the Astronomy Photography Exhibition! It was so amazing and I learned a lot of interesting stuff about space and stars.First of all, the pictures at the exhibition were out of this world! There were photos of galaxies, nebulae, and even our very own Milky Way. Some of the photographers used special telescopes to capture these images, and the details were so clear and beautiful.I also got to see photos of different planets in our solar system, like Mars and Jupiter. It was crazy to see all the different colors and textures on these planets up close. I even learnedabout some moons that orbit around these planets – did you know that Jupiter has more than 70 moons?!One of my favorite parts of the exhibition was learning about the constellations. The photographers had taken pictures of the night sky and outlined all the different constellations. I could see Orion, the Big Dipper, and even the Southern Cross. It was so cool to see how the stars connect to form these shapes.Overall, the Astronomy Photography Exhibition was a blast! I had so much fun looking at all the amazing pictures and learning about our universe. I can't wait to go back next year and see even more incredible photos. If you're into space and stars like me, this exhibition is definitely a must-see!That's all for now, see you next time! Bye!篇3Title: My Visit to the Astronomy Photography ExhibitionHi everyone! Today I want to tell you about my awesome experience at the Astronomy Photography Exhibition. It was so cool! When I walked into the exhibition hall, I saw lots of amazing pictures of stars, planets, and galaxies. They were all taken by super talented photographers. I felt like I was in outer space!One of my favorite photos was of the Milky Way. It was so beautiful and filled with twinkling stars. I also saw a picture of Saturn with its rings and a close-up of the surface of the moon. It was like I could reach out and touch them!I learned a lot of interesting things at the exhibition too. Did you know that some stars are bigger than the sun? Or that there are black holes in space that can swallow anything in their path? It’s so mind-blowing!I had so much fun going from photo to photo, learning about our amazing universe. I even got to meet some real astronomers who explained how they take these incredible pictures. They were so friendly and answered all my questions.I can’t wait to go back to the Astronomy Photography Exhibition next year. It’s the best way to learn about space and see the beauty of the universe. If you ever get a chance to visit, you should definitely go. It’s out o f this world!篇4Title: My Visit to the Astronomy Photography ExhibitionHi everyone! Today I want to tell you about my experience at the Astronomy Photography Exhibition. It was super cool!So, I went to the exhibition with my friends from school. We saw lots of amazing pictures of stars, planets, and galaxies. Some of them looked like they were from another world!One of my favorite photos was a picture of the Milky Way. It was so beautiful and bright. I also saw a photo of Jupiter with its big red spot. It looked so cool!There was a section about the moon too. We saw pictures of all the different phases of the moon. It was really interesting to see how it changes over time.We also learned about different telescopes and cameras that astronomers use to take these pictures. My friends and I even got to try out a telescope and take our own pictures of the stars.Overall, I had so much fun at the Astronomy Photography Exhibition. I learned a lot about space and got to see some really cool pictures. I can't wait to go back next year!That's all for now. Thanks for reading about my adventure at the exhibition. Bye!篇5Title: My Visit to the Astronomy Photography ExhibitionHey guys! Today I want to tell you about my super cool day at the Astronomy Photography Exhibition. It was out of this world! Literally!So, my school organized a trip to the exhibition, and I was so excited to go. When we arrived, there were huge posters of galaxies, stars, and planets everywhere. I felt like I was in outer space!I saw some amazing photographs taken by astronomers and amateur photographers. They captured the beauty of the night sky in a way that I had never seen before. I learned about different types of planets, stars, and even black holes. It was mind-blowing!One of my favorite parts was seeing the Milky Way galaxy up close. It looked like a giant swirl of stars and dust. I also saw the stunning colors of nebulae and the glowing trails of comets. I felt like I was on a space adventure!I even got to attend a workshop where I learned how to take my own astronomy photographs. I can't wait to try it out with my friends.Overall, the Astronomy Photography Exhibition was an unforgettable experience. I learned so much about the universeand our place in it. I can't wait to explore more about space in the future. I hope you guys get to visit an exhibition like this too! It's truly out of this world!篇6Title: My Amazing Experience at the Astronomy Photography ExhibitionHey guys, do you like looking at the stars and planets in the sky? Well, I went to this super cool Astronomy Photography Exhibition last week and I want to tell you all about it!The exhibition was held at the local science museum and it was all about pictures of the universe taken by telescopes and cameras. There were so many awesome photos of planets like Jupiter and Saturn, as well as different galaxies and stars. Some of the pictures looked like they were from another world – it was so amazing to see!One of my favorite parts of the exhibition was the section on the moon. They had pictures of the moon at different stages, like when it's full or just a tiny sliver. Did you know that the moon looks different depending on where you are on Earth? I didn't know that before!There was also a section on the solar system, with pictures of all the planets and their moons. I learned that some moons are bigger than planets – how crazy is that?I had so much fun at the Astronomy Photography Exhibition and I can't wait to go back next year. If you get a chance to go to one, you should definitely check it out. Who knows, maybe you'll discover something new about the universe, just like I did!篇7Once upon a time, I went to a really cool astronomy photography exhibition with my family. It was super awesome! There were so many pictures of stars, planets, and galaxies. It was like we were traveling through outer space right there in the museum.I saw pictures of the Milky Way, which is our galaxy. It looked so big and bright in the photos. I also saw pictures of Saturn with its beautiful rings and Mars with its red surface. It was so cool to see these planets up close.One of my favorite pictures was of the moon. It looked so detailed and close, like you could almost reach out and touch it. I learned that there are different phases of the moon and that itchanges shape throughout the month. It was really interesting to see all the different pictures of the moon.There were also pictures of comets and asteroids, which are like big rocks flying through space. I never knew there were so many things out there in the universe. It made me realize how big and amazing space is.Overall, the astronomy photography exhibition was a really fun and educational experience. I learned so much about the planets, stars, and galaxies. I can't wait to learn more about space and maybe even take my own astronomy photos one day. It was definitely a day to remember!篇8Title: My visit to the Astronomy Photography ExhibitionHey guys, I want to tell you all about this super cool Astronomy Photography Exhibition that I went to last weekend! It was so awesome and I saw so many amazing pictures of stars, galaxies, and planets.When I first walked in, I saw a huge picture of the Milky Way galaxy and it looked so beautiful. It made me feel like I was flying through space! There were also pictures of different planets likeMars and Jupiter. I couldn't believe how clear they looked, almost like they were right in front of me.One of my favorite pictures was of a meteor shower. It was like fireworks in the sky, but way better! I also learned a lot about the different constellations and how they look in the night sky. Did you know that some stars are millions of light years away? It's so amazing to think about how big the universe is.I had so much fun at the exhibition and I can't wait to go back again. Maybe next time I'll even bring a telescope so I can see the stars up close. If you ever get the chance to visit an Astronomy Photography Exhibition, I totally recommend it. You'll learn so much and see some truly out-of-this-world pictures!篇9Oh my gosh! I went to this super cool astronomy photography exhibition with my family last weekend and it was totally out of this world! It was like staring at the stars through a magical telescope and going on a cosmic adventure.There were pictures of galaxies, planets, stars, and even comets! I learned so much about the universe and how vast and beautiful it is. The colors and patterns in the photos were so mesmerizing, I couldn't take my eyes off of them.My favorite part was seeing the pictures of the moon up close. I never knew there were so many craters and mountains on its surface! It was like I was actually there, standing on the moon and looking back at Earth.The best part of the exhibition was when the guide showed us how the photographs were taken. It was amazing to see how much time and effort goes into capturing these incredible images. I even got to try my hand at taking a picture of the night sky with a telescope!Overall, the astronomy photography exhibition was an unforgettable experience that opened my eyes to the wonders of the universe. I can't wait to go back and learn even more about the mysteries of space. It was an adventure I'll never forget!篇10Ah! Have you guys heard about the Astronomy Photography Exhibition that's happening in our city? It's soooo cool! I went there with my friends and it was out of this world!The exhibition was held in a big hall and it was filled with all these amazing photos of space. There were pictures of stars, galaxies, planets, and even the moon! I couldn't believe how beautiful everything looked.One of my favorite photos was a picture of the Milky Way. It was so sparkly and bright, just like a million diamonds in the sky. And there was another photo of Jupiter that was super cool too. You could see all the different stripes and colors on the planet.The best part was when we got to see some photos taken by real astronomers. They had these huge telescopes and cameras to capture all the stunning images. I even got to talk to one of them and ask them all about their work. They were so nice and told me all about the different constellations and stars they had photographed.I learned so much at the exhibition and had so much fun with my friends. I can't wait to go back and see more amazing photos of space. Astronomy is so fascinating and now I want to learn even more about it!If you guys get a chance, you should definitely check out the Astronomy Photography Exhibition. It's an experience you won't forget!。

我最喜欢关于科学的书籍英语作文

我最喜欢关于科学的书籍英语作文

我最喜欢关于科学的书籍英语作文My Favorite Science BookScience is the coolest subject ever! It teaches us so many amazing things about how the world works. My favorite science book is called "Exploring the Cosmos" and it's all about outer space. It has the most incredible pictures and mind-blowing facts that make me feel like a real astronaut exploring the galaxies!The first chapter is called "The Solar System" and it starts by showing all the planets in our solar system. Did you know that the biggest planet is Jupiter? It's a massive gas giant that's so huge, over 1,300 Earths could fit inside it! And get this - it actually has a storm called the Great Red Spot that has been raging for over 300 years. How crazy is that? The book also tells us that Saturn has lots of beautiful rings around it made of billions of tiny rocks and ice chunks. I dream of one day travelling there on a spaceship to see them up close.But my absolute favorite planet is Mars, which is often called the Red Planet because its soil has a rusty reddish color from being so rich in iron. The pictures of the Martian landscape look almost alien, with its towering volcanoes, deep canyons, and those cool looking dunes shaped by wind. Some parts of Marseven used to have flowing water and lakes! Isn't that wild? The book says that one day humans might be able to live on Mars in special domed colonies. I really hope that happens because being one of the first kids living on another planet would be the best thing ever!Moving out from the planets, the book takes us deeper into space to explore stars and galaxies. It blows my mind that there are billions and billions of stars out there, each one a burning ball of superhot gas like our Sun. They come in different colors too - red, blue, yellow, and white. The oldest stars are actually nearing the end of their lives and will eventually explode into beautiful clouds called nebulas, which is where new stars are born from the leftover gas and dust. It's like a endless cosmic cycle of stars being born, living, and then dying, creating more new stars. The universe is so amazing!My favorite chapter is the one on galaxies because it has the most dazzling pictures that make me feel like I'm floating through outer space. Our own Milky Way galaxy contains over 200 billion stars all swirling together in this huge spinning spiral. From far away, galaxies almost look like shining frisbees or pinwheels in the blackness of space. There are so many different types too - elliptical ones that are cloudlike, irregular galaxiesthat are blobby and misshapen, and incredible spiral galaxies with long arms curving around. The most distant galaxies we can see are actually from when the universe was just a baby, only a few billion years old!The book talks about how galaxies are gravitationally bound clusters, which means the incredible force of gravity is what holds them together and makes them spin. Apparently in the middle of every galaxy is a supermassive black hole - the most powerful gravity monster imaginable. These totally weird and fascinating black holes actually warp the very fabric of space and time around them. Just thinking about that bends my brain! The pictures look like shimmering cosmic tunnels reaching deep into an endless abyss. I could stare at those black hole images for hours, wondering what profound secrets lie within.At the very end, the book talks about some of the biggest mysteries that scientists today are still trying to solve, like what exactly is dark matter and dark energy? How did our universe begin in the first Big Bang? And is there other intelligent alien life somewhere out there amongst the billions of galaxies? Those are such exciting and profound questions that make me want to become an astrophysicist when I grow up so I can help unravel those cosmic puzzles!"Exploring the Cosmos" is hands down my favorite book because it fills my head with such jaw-dropping facts and beautiful images about the incredible universe we live in. Reading it inspires me to keep exploring, learning, and never stop being curious about the world around me. I can't wait to see what other amazing space discoveries happen in my lifetime. Who knows, maybe one day I'll even get to walk on Mars or see a supernova exploding with my own eyes! The cosmos is our tiny home in this vast, ancient universe just waiting to be uncovered. And books like this make me feel like I can reach out and touch the stars.。

英语作文-探索太空奥秘,感受宇宙的神秘

英语作文-探索太空奥秘,感受宇宙的神秘

英语作文-探索太空奥秘,感受宇宙的神秘The cosmos has always been a canvas of intrigue and mystery, a vast expanse that beckons the curious and the brave. It is a place where the laws of physics are pushed to their limits and sometimes, even beyond our understanding. The exploration of space is not just a journey through the physical dimensions of distance and time, but also an expedition into the very essence of our existence.In the silent void of space, stars are born and die in spectacular fashion, galaxies collide and dance in a cosmic ballet, and black holes lurk in the shadows, swallowing everything that dares to venture too close. Each of these phenomena tells a story—a narrative of the universe's past, present, and future.The quest to unravel the secrets of space has led humanity to remarkable discoveries. We have sent probes to distant planets, landed on asteroids, and peered into the deepest corners of the universe with powerful telescopes. These eyes in the sky have revealed wonders such as the rings of Saturn, the red deserts of Mars, and the icy geysers of Europa.Yet, for all that we have learned, the universe remains a place of profound mystery. There are questions that still elude us: What is dark matter? Why is the expansion of the universe accelerating? Are we alone, or is the cosmos teeming with life in forms we can scarcely imagine?The answers to these questions may reshape our understanding of our place in the cosmos. They may tell us not just about the universe out there, but also about the universe within—the human spirit that yearns to explore, to understand, and to connect.Space exploration is a testament to our innate curiosity and our relentless pursuit of knowledge. It is a journey that has the power to unite us in wonder and aspiration. As we stand on the precipice of new discoveries, we are reminded that the universe is not just something to be studied—it is something to be experienced. It is a reminder that, in thegrand tapestry of existence, we are both observers and participants in the unfolding story of the cosmos.In this journey, technology and imagination are our greatest allies. They allow us to build spacecraft that can withstand the harsh conditions of space, to simulate environments that are millions of miles away, and to visualize scenarios that push the boundaries of what we believe is possible.As we continue to explore the vastness of space, we do so with a sense of humility and a recognition of our own limitations. The universe is far more complex and mysterious than we once thought, and each discovery leads to new questions, new challenges, and a deeper appreciation for the enigma that is space.In conclusion, the exploration of space is more than a scientific endeavor; it is a journey of the human spirit. It is a pursuit that calls to the dreamers, the thinkers, the artists, and the engineers. It is an invitation to gaze up at the night sky and feel a connection to the stars that twinkle back, as if to say, "Come, explore, and be amazed." For in the pursuit of the cosmos, we find not only the secrets of the universe but also the potential of our own boundless imagination. 。

小学上册I卷英语第四单元期末试卷

小学上册I卷英语第四单元期末试卷

小学上册英语第四单元期末试卷英语试题一、综合题(本题有100小题,每小题1分,共100分.每小题不选、错误,均不给分)1.The __________ (自然美) inspires artists.2.My mom is cooking ________ for dinner.3.The _____ (风) can carry seeds far away.4.I can’t wait to have a __________ (形容词) __________ (玩具名) party.5.Fossils provide evidence of ______ life on Earth.6.I wear _____ (运动鞋) to school.7.What is the main ingredient in sushi?A. RiceB. NoodlesC. BreadD. PotatoesA8.My favorite color is _______ (blue/red).9.What is the first letter of the alphabet?A. AB. BC. CD. D10.Which animal is known for its distinctive black and white coloring?A. PandaB. ZebraC. SkunkD. Orca11.What do you call a baby rabbit?A. KitB. PupC. CalfD. Cub12.My brother is a ______. He enjoys building robots.13.The _____ (squirrel) is in the tree.14.What do you call a large body of water?A. RiverB. OceanC. PondD. Lake15.The flowers are _____ (pretty/ugly).16.I want to learn to ______.17.y of Versailles imposed harsh penalties on ________ (德国). The Trea18.My friend is a committed __________ (志愿者).19.What do we call the large body of salt water that covers most of the Earth?A. SeaB. OceanC. BayD. Gulf20.What is the name of the famous mountain located in Africa?A. KilimanjaroB. DenaliC. EverestD. Elbrus21.What is the main ingredient in mayonnaise?A. EggB. OilC. VinegarD. All of the above22.They are ___ a project. (finishing)23.She is ________ a book.24. A __________ solution has more solute than it can dissolve.25.What is the capital city of Papua New Guinea?A. Port MoresbyB. LaeC. Mount HagenD. Madang26.What is the capital of Afghanistan?A. KabulB. HeratC. KandaharD. Mazar-i-Sharif27.Some fish can glow in the ______.28.She can ___ (sing/dance) very well.29.My dad teaches me to be __________ (负责的) with my chores.30.My grandma has a lovely _____ at her house.31.The chemical symbol for gallium is __________.32.The flowers are _____ in the garden. (growing)33.What is the main ingredient in minestrone soup?A. BeansB. PastaC. VegetablesD. All of the above34.The Earth's atmosphere is made up of different gases, primarily ______.35.The ancient Greeks held their athletic competitions in honor of ______ (宙斯).36. A solution that contains a large amount of solute compared to solvent is called______.37. A solution that is unable to dissolve more solute is called ______.38.What is the opposite of hot?A. WarmB. CoolC. ColdD. FreezingC39.The element with the symbol V is __________.40.Chemical reactions are affected by factors such as temperature, concentration, and ______.41.What do you call a baby dog?A. KittenB. CubC. PuppyD. ChickC42.The volcano is _______ (active).43.The earth orbits around the ______ (sun).44.I like to wear ___ (hats) in the sun.45.My teacher is very __________ (和蔼可亲).46.The _____ (狮子) rests in the shade during the hot day.47.My favorite childhood memory is __________ because it was so much fun.48.What is the capital of Germany?A. MunichB. BerlinC. FrankfurtD. HamburgB49.I like to ride my ______ (scooter).50.Which animal is known for its ability to change color?A. ChameleonB. ElephantC. TigerD. Kangaroo51.Astronomers use radio waves to study _______ objects.52.Which month comes after April?A. MarchB. MayC. JuneD. JulyB53.Which animal is known for its intelligence and problem-solving skills?A. DogB. CatC. DolphinD. ElephantC54.How many colors are in a standard traffic light?A. 2B. 3C. 4D. 555. A ________ (草原) is full of grasses.56.Gardening can provide a sense of ______ and satisfaction. (园艺可以带来成就感和满足感。

中性黑环时空中费米子的隧穿

中性黑环时空中费米子的隧穿

中性黑环时空中费米子的隧穿陈德友【摘要】研究五维时空中费米子的隧穿特征通常需要构造五个伽马矩阵.在本文中,我们以一个五维中性黑环为例,通过降维技术将五维降为四维,在四维时空中构造矩阵,对黑环的费米子隧穿辐射进行了研究.其研究结果表明,四维时空中同样可以得到五维黑环的霍金温度.【期刊名称】《西华师范大学学报(自然科学版)》【年(卷),期】2014(035)001【总页数】3页(P1-3)【关键词】中性黑环;隧穿效应;费米子【作者】陈德友【作者单位】西华师范大学理论物理研究所,四川南充637009【正文语种】中文【中图分类】P145.6最近的研究表明[1,2],四维黑洞的温度可以通过费米子隧穿视界得到.在该研究中,人们无需假设粒子出射路径沿径向方向[3].为了求解粒子的作用量,人们首先需要构造伽马矩阵,以及假设费米子出射波函数的表达形式.最后,通过半经典近似得到粒子的隧穿率以及黑洞的温度.该方法的关键是构造伽马矩阵.将该工作推广到高维时空,五维以及六维时空中费米子的隧穿特性被研究[4,5].四维时空中的矩阵能很好的构造,然而,高维时空中的矩阵比较难构造.本文将以一个五维中性黑环为例,通过降维技术,将五维降为四维,达到简化构造伽马矩阵的目的,在四维中研究五维时空中费米子的隧穿特性.其结果表明,四维时空中同样可以得到五维时空视界处的霍金温度.中性黑环的度规给出如下[6]:ds2=其中,F(ξ)=1+λξ,G(ξ)=(1+vξ)(1-ξ2),C(v,λ)=.v、λ是无维度的参数,且满足0<v≤λ<1.为了避免在x=-1和y=-1处奇异性的产生,φ、ψ选取具有2π的周期性.该环的视界位置在y=yh=- .为了方便研究粒子的隧穿特性,上述度规可以表示为ds2=-A(x,y)dt2+B-1(x,y)dy2+gψψ(dψ+N(x,y)dt)2+gxxdx2+gφφdφ2在视界处A(x,yh)=B(x,yh)=0,Ωh=-N(x,yh).一般情况下,人们直接从上述度规研究费米子在该时空中的隧穿特性.但在五维时空中不利于构造伽马矩阵.为了方便构造伽马矩阵,我们在四维时空中研究该五维度规.因此,我们对度规(2)进行坐标变换dψ=-N(x,y)dt,得到ds2=-f(x,y)dt2+g-1(x,y)dy2+gxxdx2+gφφdφ2,其中f(x,y)=,g(x,y)=-.费米子的运动方程满足弯曲时空中的狄拉克方程iγμ(∂μ+Ωμ)ψ+ψ=0,其中,矩阵满足关系式{γμ,γu}=2gμv,m是隧穿粒子的质量.我们选择如下γμ 矩阵对于自旋为1/2的粒子,这里有自旋向上和向下两个态,它们对应的波函数分别为我们选取向上态的波函数进行研究.将波函数和伽马矩阵带入狄拉克方程,整理后得到这个方程很难直接从上面方程中得出作用量的表达形式.考虑到时空的特性,我们进行变量分离如下I↑=-(ω-jΩ)t+W(y)+X(x,φ),其中,ω是隧穿粒子的能量,j和Ω分别对应于角动量和角速度.将作用量带入方程(9)、(10),可以得到复函数的X(x,φ)解.我们感兴趣的是方程(7)、(8),因为,隧穿率由此决定.将作用量带入后,得到在视界处解得到在上面方程中,+(-)分别对应出射(入射)解,Ω+是视界处的角速度,f′(x,yh)=,g′(x,yh)= .因此,粒子的隧穿率为[7]Γ===所以,在黑环视界处的霍金温度为T==.在上面的讨论中,我们把五维时空降为四维,在四维时空中得到了五维中性黑环的温度.综上,在反常取消的研究方法中[8],人们考虑到视界附件的性质,通过降维技术,将高维时空降为二维.通过反常抵消的方法,同样可以得到视界处的温度.在本文中,我们同样可以采用此方法进行研究,相同的霍金温度可以得到.【相关文献】[1] KERNER R,MANN R B.Charged Fermions Tunnelling from Kerr-Newman Black Holes [J].Phys Lett B,2008,665:277-283.[2] CHEN D,JIANG Q Q,ZU X T.Fermions Tunnelling from the Charged Dilatonic BlackHoles [J].Class Quant Grav,2008,25:205022.[3] PARIKH M P,WILCZEK F.Hawking Rradiation as Tunneling [J].Phys Rev Lett,2000,85:5042-5045.[4] JIANG Q Q.Dirac Particles’ Tunnelling from Black Rings [J].Phys Rev D,2008,78:044009.[5] LIN K,YANG S Z.Fermion Tunneling from Higher-Dimensional Black Holes [J].Phys Rev D,2009,79:064035.[6] EMPARAN R.Rotating Circular Strings,and Infinite Non-uniqueness of Black rings [J].JHEP,2004,03:064.[7] MITRA P.Hawking Temperature from Tunnelling Formalism [J].Phys Lett B,2007,648:240-242.[8] ROBINSON S P,WILCZEK F.A Relationship Between Hawking Radiation And Gravitational Anomalies [J].Phys Rev Lett,2005,95:011303.。

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a rXiv:h ep-th/054126v21Fe b26hep-th/05041265D Black Rings and 4D Black Holes Davide Gaiotto*,Andrew Strominger*and Xi Yin*Center of Mathematical Sciences Zhejiang University,Hangzhou 310027China Abstract It has recently been shown that the M theory lift of a IIA 4D BPS Calabi-Yau black hole is a 5D BPS black hole spinning at the center of a Taub-NUT-flux geometries,and a certain linear relation between 4D and 5D BPS partition functions was accordingly proposed.In the present work we fortify and enrich this proposal by showing that the M-theory lift of the general 4D multi-black hole geometry are 5D black rings in a Taub-NUT-flux geometry.Contents1.Introduction (1)2.Multicenter BPS solutions in4D (2)3.5D solutions (4)4.4D→5D lift (5)1.IntroductionIn a recent paper[1]it was shown that the M-theory lift of a general4D BPS Calabi-Yau black hole can be viewed as a5D BPS spinning black hole[2]sitting in the center of aflux-Taub-NUT spacetime.This suggested a direct relation between the microstates of 4D and5D black holes,and(invoking[3])motivated a conjecture of the formZ5D=Z4D=|Z top|2,(1.1)relating a4D BPS partition function,a5D BPS partition function and the topological string.See[1]for the precise form of and arguments appearing in(1.1).A recent surprise[4]is that BPS objects in5D include black rings as well as black holes.The5D partition function Z5D should include all BPS states,in particular black rings.A check of our conjecture is then that Z4D must include a contribution to match the5D black rings in Z5D.Indeed we will show that there is just such a matching contribution.In a series of beautiful papers[5,6,7]Denef and collaborators have explicitly constructed multi-center 4D BPS black hole solutions which in general carry angular momenta.The black holes in these solutions can have different sets of charges and they are bound to one another in the sense that the black holes separations arefixed in terms of their charges and the asymptotic values of the moduli.In this paper we will construct exact”flux-Taub-NUT-black-ring”solutions describing a black ring in Taub-NUT with four-formflux turned on.We further show that these solutions are precisely the lift to5D of the Denef multi-center solutions, and the4D black hole separations become the radii of the5D rings.This result fortifies and enriches the4D-5D connection proposed in[1],and will also clearly have implications for our understanding of the topological string.1This paper is organized as follows.Section2reviews the multi-center black hole solutions.Section3constructs a general solution of5D supergravity describing black rings and black holes in a multi-Taub-NUT-flux geometry.In section4we show that section3 is the M-theory lift of section2,and describe the basic example of lifting the bound state of a D6-brane with a D4-D2-D0black hole to a5D black ring.2.Multicenter BPS solutions in4DIn this section we review,and slightly reformulate,the general multi-center BPS so-lution of4D N=2supergravity2found in[7].The solution is characterized by electro-magnetic charges and asymptotic moduli.It may be expressed in terms of2h11+2real harmonic functions on R3HΛ( x)HΛ( x) =hΛhΛ+spΛi qΛ,i1π∂S bh(pΛ,qΛ)2Im[CXΛ¯C¯FΛ].(2.3)In order tofind S bh as a function of charges,as needed in(2.2),one must solve the algebraic attractor equations[11,12].This may or may not be analytically possible,depending on the form of the prepotential and the charge vector.Note that the S bh used here is a function of position and is equal to the black hole entropy only at the horizon.The constants h encode the values of the moduli at spatial infinity,i.e.Re[CXΛ(∞)]=hΛ,Re[CFΛ(∞)]=hΛ.Given the modulifields XΛ( x)the four dimensional metric is then simplyds24=−ππd x2,(2.4)where it is implicit that S bh=S bh(XΛ( x))andω(4)is the solution ofdω(4)=HΛ∗3dHΛ−HΛ∗3dHΛ.(2.5) The gaugefields strengths aredAΛ=d S−1bh∂S bhR2 T N +1(r2+L2−2rL cosθ)1(r2+L2−2rL cosθ)1L +q02(2.8)The integrability condition(2.7)is then1R2T N =h A p A3.5D solutionsThis section will describe some new supersymmetric 5D black ring-Taub-NUT-flux solutions which generalize previous solutions of minimal supergravity [4,13].In the next section we will seetheyare simply the lift to 5D of the 4D multicenter solutions reviewed in the previous section.N =2supergravity fields in 5D are organized by the so-called very special geometry[14],parameterized by h 11real scalar fields Y A ,subject to the constraintD ABC Y A Y B Y C =1,(3.1)for constant couplings D ABC .It is useful to further defineY A ≡3D ABC Y B Y C .(3.2)BPS solutions in 5D N =2supergravity may be written following [15,16,17,13]ds 25=−2−4/3f −2(dt +ω)2+22/3fds 2X F A =d f −1Y A (dt +ω) +ΘA (3.3)where ds 2X is hyperk¨a ler metric on a 4D hyperk¨a ler space X ,ΘA are closed self-dual 2-forms on X ,the self-dual part of dωis −fY A ΘA and f is a function on X obeying∇2(fY A )=3D ABC ΘB ·ΘC .(3.4)When the space X is Taub-NUT,3one hasds 2X =H 0( x )d x 2+H 0( x )−1(dx 5+ω0)2,dω0=∗3dH 0,(3.5)with H 0a harmonic function as in (2.8),and the coordinate x 5has periodicity 4π.Closed self-dual 2-forms are then given byΘA =d H AH 0·∇ H C 3The more general solution with X being a Gibbons-Hawking space was presented in [17].This is magically solved byfY A =H A +3D ABC H B H C(H 0)2+H A H AX 0of 4D supergravity,a solution of 5Dsupergravity is quite generally given byds 25D =22/3V 2(dx 5+A 04D )2+2−1/3V −1ds 24D ,A A 5D =A A 4D +Re z A (dx 5+A 04D ),Y A =V −1Im z A ,V ≡ D ABC Im z A Im z B Im zC 1X 0.(4.2)The expression for the entropy as a function of the charges is known,although complicated[19].It isS (p,q )=2π2=D ABC y A y B y C ,3D ABC y A yB =qC +3D ABC p A p B 2+D ABC p A p B p C2p 0.(4.3)Correspondingly there will be certain functions Q( x)and J( x)built out of the harmonic functions(HΛ( x),HΛ( x)).The volume of the Calabi-Yau at x is V( x)3,withS(HΛ,HΛ)V( x)=,(4.5)becomes precisely the black ring solution inflatr5D spacetime[4].The radius of the ring is R ring=L.It is constructed from wrapped M5branes with charges p A,carries M2charges˜q A=q A+3D ABC p B p C and SU(2)L spin J L=q0/2.Note that the entropy of the two-centered black hole comes from only the D4-D2-D0 system.It is amusing to verify directly that the tree level entropy of the D4-D2-D0system of charge(p A,q A,q0)indeed agrees with that of the black ring[20],[21]with M5-M2charge (p A,˜q A)and angular momentum J L=q0/2.More generally,when there are mulitple4D black holes carrying D6charge,the back-ground geometry of the5D lift will be a resolved multi-Taub-Nut-flux geometry.The black holes of the4D solution that carry D6charges will lift to5D spinning black holes at the fixed points of the U(1)L isometry of the multi-Taub-NUT background.Those that do not will lift to5D black rings tracing orbits of the isometry.AcknowledgementsWe would like to thank M.Guica for useful conversations.This work was supported in part by DOE grant DE-FG02-91ER40654.References[1] D.Gaiotto,A.Strominger and X.Yin,“New Connections Between4D and5D BlackHoles,”arXiv:hep-th/0503217.[2]J.C.Breckenridge,R.C.Myers,A.W.Peet and C.Vafa,“D-branes and Spinning BlackHoles”,hep-th/9602065.[3]H.Ooguri,A.Strominger and C.Vafa,“Black hole attractors and the topologicalstring,”arXiv:hep-th/0405146.[4]H.Elvang,R.Emparan,D.Mateos and H.S.Reall,“A supersymmetric black ring,”Phys.Rev.Lett.93,211302(2004)[arXiv:hep-th/0407065].[5] F.Denef,“Supergravityflows and D-brane stability,”JHEP0008,050(2000)[arXiv:hep-th/0005049].[6] F.Denef,B.R.Greene and M.Raugas,“Split attractorflows and the spectrum ofBPS D-branes on the quintic,”JHEP0105,012(2001)[arXiv:hep-th/0101135]. [7] B.Bates and F.Denef,“Exact solutions for supersymmetric stationary black holecomposites,”arXiv:hep-th/0304094.[8]G.W.Moore,“Attractors and arithmetic,”arXiv:hep-th/9807056.[9]G.W.Moore,“Arithmetic and attractors,”arXiv:hep-th/9807087.[10]G.W.Moore,“Les Houches lectures on strings and arithmetic,”arXiv:hep-th/0401049.[11]S.Ferrara,R.Kallosh and A.Strominger,“N=2extremal black holes,”Phys.Rev.D52,5412(1995)[arXiv:hep-th/9508072].[12] A.Strominger,“Macroscopic Entropy of N=2Extremal Black Holes,”Phys.Lett.B383,39(1996)[arXiv:hep-th/9602111].[13]P.Kraus and rsen,“Attractors and black rings,”arXiv:hep-th/0503219.[14]M.Gunaydin,G.Sierra and P.K.Townsend,“Gauging The D=5Maxwell-EinsteinSupergravity Theories:More On Jordan Algebras,”Nucl.Phys.B253,573(1985).[15]J.P.Gauntlett,J.B.Gutowski,C.M.Hull,S.Pakis and H.S.Reall,“All supersym-metric solutions of minimal supergravity infive dimensions,”Class.Quant.Grav.20, 4587(2003)[arXiv:hep-th/0209114].[16]J.B.Gutowski and H.S.Reall,“General supersymmetric AdS(5)black holes,”JHEP0404,048(2004)[arXiv:hep-th/0401129].[17]J.P.Gauntlett and J.B.Gutowski,“General concentric black rings,”Phys.Rev.D71,045002(2005)[arXiv:hep-th/0408122].[18]R.Gregory,J.A.Harvey and G.W.Moore,“Unwinding strings and T-duality ofKaluza-Klein and H-monopoles,”Adv.Theor.Math.Phys.1,283(1997)[arXiv:hep-th/9708086].[19]M.Shmakova,‘Calabi-Yau black holes,”Phys.Rev.D56,540(1997)[arXiv:hep-th/9612076].[20]I.Bena and P.Kraus,“Microscopic description of black rings in AdS/CFT,”JHEP0412,070(2004)[arXiv:hep-th/0408186].[21]M.Cyrier,M.Guica,D.Mateos and A.Strominger,“Microscopic entropy of the blackring,”arXiv:hep-th/0411187.。

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